If there is a WAL segment with same ID but different TLI present in both
the WAL archive and pg_xlog, prefer the one with higher TLI. Before this
patch, the archive was polled first, for all expected TLIs, and only if no
file was found was pg_xlog scanned. This was a change in behavior from 9.3,
which first scanned archive and pg_xlog for the highest TLI, then archive
and pg_xlog for the next highest TLI and so forth. This patch reverts the
behavior back to what it was in 9.2.
The reason for this is that if for example you try to do archive recovery
to timeline 2, which branched off timeline 1, but the WAL for timeline 2 is
not archived yet, we would replay past the timeline switch point on
timeline 1 using the archived files, before even looking timeline 2's files
in pg_xlog
Report and patch by Kyotaro Horiguchi. Backpatch to 9.3 where the behavior
was changed.
Previously we were piggybacking on transaction ID parameters to freeze
multixacts; but since there isn't necessarily any relationship between
rates of Xid and multixact consumption, this turns out not to be a good
idea.
Therefore, we now have multixact-specific freezing parameters:
vacuum_multixact_freeze_min_age: when to remove multis as we come across
them in vacuum (default to 5 million, i.e. early in comparison to Xid's
default of 50 million)
vacuum_multixact_freeze_table_age: when to force whole-table scans
instead of scanning only the pages marked as not all visible in
visibility map (default to 150 million, same as for Xids). Whichever of
both which reaches the 150 million mark earlier will cause a whole-table
scan.
autovacuum_multixact_freeze_max_age: when for cause emergency,
uninterruptible whole-table scans (default to 400 million, double as
that for Xids). This means there shouldn't be more frequent emergency
vacuuming than previously, unless multixacts are being used very
rapidly.
Backpatch to 9.3 where multixacts were made to persist enough to require
freezing. To avoid an ABI break in 9.3, VacuumStmt has a couple of
fields in an unnatural place, and StdRdOptions is split in two so that
the newly added fields can go at the end.
Patch by me, reviewed by Robert Haas, with additional input from Andres
Freund and Tom Lane.
In a database that's not yet reached consistency, it's possible that some
segments of a relation are not full-size but are not the last ones either.
Because of the way smgrnblocks() works, asking for a new page with P_NEW
will fill in the last not-full-size segment --- and if that makes it full
size, the apparent EOF of the relation will increase by more than one page,
so that the next P_NEW request will yield a page past the next consecutive
one. This breaks the relation-extension logic in XLogReadBufferExtended,
possibly allowing a page update to be applied to some page far past where
it was intended to go. This appears to be the explanation for reports of
table bloat on replication slaves compared to their masters, and probably
explains some corrupted-slave reports as well.
Fix the loop to check the page number it actually got, rather than merely
Assert()'ing that dead reckoning got it to the desired place. AFAICT,
there are no other places that make assumptions about exactly which page
they'll get from P_NEW.
Problem identified by Greg Stark, though this is not the same as his
proposed patch.
It's been like this for a long time, so back-patch to all supported
branches.
WakeupWaiters() is supposed to wake up all LW_WAIT_UNTIL_FREE waiters of
the slot, but the loop incorrectly also woke up the first LW_EXCLUSIVE
waiter, if there was no LW_WAIT_UNTIL_FREE waiters in the queue.
Noted by Andres Freund. This code is new in 9.4, so no backpatching.
Replication slots are a crash-safe data structure which can be created
on either a master or a standby to prevent premature removal of
write-ahead log segments needed by a standby, as well as (with
hot_standby_feedback=on) pruning of tuples whose removal would cause
replication conflicts. Slots have some advantages over existing
techniques, as explained in the documentation.
In a few places, we refer to the type of replication slots introduced
by this patch as "physical" slots, because forthcoming patches for
logical decoding will also have slots, but with somewhat different
properties.
Andres Freund and Robert Haas
This makes it possible to store lwlocks as part of some other data
structure in the main shared memory segment, or in a dynamic shared
memory segment. There is still a main LWLock array and this patch does
not move anything out of it, but it provides necessary infrastructure
for doing that in the future.
This change is likely to increase the size of LWLockPadded on some
platforms, especially 32-bit platforms where it was previously only
16 bytes.
Patch by me. Review by Andres Freund and KaiGai Kohei.
This allows ending recovery as a consistent state has been reached. Without
this, there was no easy way to e.g restore an online backup, without
replaying any extra WAL after the backup ended.
MauMau and me.
Since C99, it's been standard for printf and friends to accept a "z" size
modifier, meaning "whatever size size_t has". Up to now we've generally
dealt with printing size_t values by explicitly casting them to unsigned
long and using the "l" modifier; but this is really the wrong thing on
platforms where pointers are wider than longs (such as Win64). So let's
start using "z" instead. To ensure we can do that on all platforms, teach
src/port/snprintf.c to understand "z", and add a configure test to force
use of that implementation when the platform's version doesn't handle "z".
Having done that, modify a bunch of places that were using the
unsigned-long hack to use "z" instead. This patch doesn't pretend to have
gotten everyplace that could benefit, but it catches many of them. I made
an effort in particular to ensure that all uses of the same error message
text were updated together, so as not to increase the number of
translatable strings.
It's possible that this change will result in format-string warnings from
pre-C99 compilers. We might have to reconsider if there are any popular
compilers that will warn about this; but let's start by seeing what the
buildfarm thinks.
Andres Freund, with a little additional work by me
In ordinary operation, VACUUM must be careful to take a cleanup lock on
each leaf page of a btree index; this ensures that no indexscans could
still be "in flight" to heap tuples due to be deleted. (Because of
possible index-tuple motion due to concurrent page splits, it's not enough
to lock only the pages we're deleting index tuples from.) In Hot Standby,
the WAL replay process must likewise lock every leaf page. There were
several bugs in the code for that:
* The replay scan might come across unused, all-zero pages in the index.
While btree_xlog_vacuum itself did the right thing (ie, nothing) with
such pages, xlogutils.c supposed that such pages must be corrupt and
would throw an error. This accounts for various reports of replication
failures with "PANIC: WAL contains references to invalid pages". To
fix, add a ReadBufferMode value that instructs XLogReadBufferExtended
not to complain when we're doing this.
* btree_xlog_vacuum performed the extra locking if standbyState ==
STANDBY_SNAPSHOT_READY, but that's not the correct test: we won't open up
for hot standby queries until the database has reached consistency, and
we don't want to do the extra locking till then either, for fear of reading
corrupted pages (which bufmgr.c would complain about). Fix by exporting a
new function from xlog.c that will report whether we're actually in hot
standby replay mode.
* To ensure full coverage of the index in the replay scan, btvacuumscan
would emit a dummy WAL record for the last page of the index, if no
vacuuming work had been done on that page. However, if the last page
of the index is all-zero, that would result in corruption of said page,
since the functions called on it weren't prepared to handle that case.
There's no need to lock any such pages, so change the logic to target
the last normal leaf page instead.
The first two of these bugs were diagnosed by Andres Freund, the other one
by me. Fixes based on ideas from Heikki Linnakangas and myself.
This has been wrong since Hot Standby was introduced, so back-patch to 9.0.
Makes the replay loop slightly more readable, by separating the concerns of
whether to stop and whether to delay, and how to extract the timestamp from
a record.
This has the user-visible change that the timestamp of the last applied
record is now updated after actually applying it. Before, it was updated
just before applying it. That meant that pg_last_xact_replay_timestamp()
could return the timestamp of a commit record that is in process of being
replayed, but not yet applied. Normally the difference is small, but if
min_recovery_apply_delay is set, there could be a significant delay between
reading a record and applying it.
Another behavioral change is that if you recover to a restore point, we stop
after the restore point record, not before it. It makes no difference as far
as running queries on the server is concerned, as applying a restore point
record changes nothing, but if examine the timeline history you will see
that the new timeline branched off just after the restore point record, not
before it. One practical consequence is that if you do PITR to the new
timeline, and set recovery target to the same named restore point again, it
will find and stop recovery at the same restore point. Conceptually, I think
it makes more sense to consider the restore point as part of the new
timeline's history than not.
In principle, setting the last-replayed timestamp before actually applying
the record was a bug all along, but it doesn't seem worth the risk to
backpatch, since min_recovery_apply_delay was only added in 9.4.
If pause_at_recovery_target is set, recovery pauses *before* applying the
target record, even if recovery_target_inclusive is set. If you then
continue with pg_xlog_replay_resume(), it will apply the target record
before ending recovery. In other words, if you log in while it's paused
and verify that the database looks OK, ending recovery changes its state
again, possibly destroying data that you were tring to salvage with PITR.
Backpatch to 9.1, this has been broken since pause_at_recovery_target was
added.
The docs say that only one of recovery_target_xid, recovery_target_time, or
recovery_target_name can be specified. But the code actually did something
different, so that a name overrode time, and xid overrode both time and name.
Now the target specified last takes effect, whether it's an xid, time or
name.
With this patch, we still accept multiple recovery_target settings, even
though docs say that only one can be specified. It's a general property of
the recovery.conf file parser that you if you specify the same option twice,
the last one takes effect, like with postgresql.conf.
When starting WAL replay from an online checkpoint, the last replayed WAL
record variable was initialized using the checkpoint record's location, even
though the records between the REDO location and the checkpoint record had
not been replayed yet. That was noted as "slightly confusing" but harmless
in the comment, but in some cases, it fooled CheckRecoveryConsistency to
incorrectly conclude that we had already reached a consistent state
immediately at the beginning of WAL replay. That caused the system to accept
read-only connections in hot standby mode too early, and also PANICs with
message "WAL contains references to invalid pages".
Fix by initializing the variables to the REDO location instead.
In 9.2 and above, change CheckRecoveryConsistency() to use
lastReplayedEndRecPtr variable when checking if backup end location has
been reached. It was inconsistently using EndRecPtr for that check, but
lastReplayedEndRecPtr when checking min recovery point. It made no
difference before this patch, because in all the places where
CheckRecoveryConsistency was called the two variables were the same, but
it was always an accident waiting to happen, and would have been wrong
after this patch anyway.
Report and analysis by Tomonari Katsumata, bug #8686. Backpatch to 9.0,
where hot standby was introduced.
And the same for do_pg_stop_backup. The code in do_pg_* is not allowed
to access the catalogs. For manual base backups, the permissions
check can be handled in the calling function, and for streaming
base backups only users with the required permissions can get past
the authentication step in the first place.
Reported by Antonin Houska, diagnosed by Andres Freund
Original users of slru.c were all producing 4-digit filenames, so that
was all that that code was prepared to handle. Changes to multixact.c
in the course of commit 0ac5ad5134 made pg_multixact/members create
5-digit filenames once a certain threshold was reached, which
SlruScanDirectory wasn't prepared to deal with; in particular,
5-digit-name files were not removed during truncation. Change that
routine to make it aware of those files, and have it process them just
like any others.
Right now, some pg_multixact/members directories will contain a mixture
of 4-char and 5-char filenames. A future commit is expected fix things
so that each slru.c user declares the correct maximum width for the
files it produces, to avoid such unsightly mixtures.
Noticed while investigating bug #8673 reported by Serge Negodyuck.
In the 9.2 code for extending multixact/members, the logic was very
simple because the number of entries in a members page was a proper
divisor of 2^32, and thus at 2^32 wraparound the logic for page switch
was identical than at any other page boundary. In commit 0ac5ad5134 I
failed to realize this and introduced code that was not able to go over
the 2^32 boundary. Fix that by ensuring that when we reach the last
page of the last segment we correctly zero the initial page of the
initial segment, using correct uint32-wraparound-safe arithmetic.
Noticed while investigating bug #8673 reported by Serge Negodyuck, as
diagnosed by Andres Freund.
In pg_multixact/members, relying on modulo-2^32 arithmetic for
wraparound handling doesn't work all that well. Because we don't
explicitely track wraparound of the allocation counter for members, it
is possible that the "live" area exceeds 2^31 entries; trying to remove
SLRU segments that are "old" according to the original logic might lead
to removal of segments still in use. To fix, have the truncation
routine use a tailored SlruScanDirectory callback that keeps track of
the live area in actual use; that way, when the live range exceeds 2^31
entries, the oldest segments still live will not get removed untimely.
This new SlruScanDir callback needs to take care not to remove segments
that are "in the future": if new SLRU segments appear while the
truncation is ongoing, make sure we don't remove them. This requires
examination of shared memory state to recheck for false positives, but
testing suggests that this doesn't cause a problem. The original coding
didn't suffer from this pitfall because segments created when truncation
is running are never considered to be removable.
Per Andres Freund's investigation of bug #8673 reported by Serge
Negodyuck.
If a tuple was locked by transaction A, and transaction B updated it,
the new version of the tuple created by B would be locked by A, yet
visible only to B; due to an oversight in HeapTupleSatisfiesUpdate, the
lock held by A wouldn't get checked if transaction B later deleted (or
key-updated) the new version of the tuple. This might cause referential
integrity checks to give false positives (that is, allow deletes that
should have been rejected).
This is an easy oversight to have made, because prior to improved tuple
locks in commit 0ac5ad5134 it wasn't possible to have tuples created by
our own transaction that were also locked by remote transactions, and so
locks weren't even considered in that code path.
It is recommended that foreign keys be rechecked manually in bulk after
installing this update, in case some referenced rows are missing with
some referencing row remaining.
Per bug reported by Daniel Wood in
CAPweHKe5QQ1747X2c0tA=5zf4YnS2xcvGf13Opd-1Mq24rF1cQ@mail.gmail.com
Tuple freezing was broken in connection to MultiXactIds; commit
8e53ae025d tried to fix it, but didn't go far enough. As noted by
Noah Misch, freezing a tuple whose Xmax is a multi containing an aborted
update might cause locks in the multi to go ignored by later
transactions. This is because the code depended on a multixact above
their cutoff point not having any lock-only member older than the cutoff
point for Xids, which is easily defeated in READ COMMITTED transactions.
The fix for this involves creating a new MultiXactId when necessary.
But this cannot be done during WAL replay, and moreover multixact
examination requires using CLOG access routines which are not supposed
to be used during WAL replay either; so tuple freezing cannot be done
with the old freeze WAL record. Therefore, separate the freezing
computation from its execution, and change the WAL record to carry all
necessary information. At WAL replay time, it's easy to re-execute
freezing because we don't need to re-compute the new infomask/Xmax
values but just take them from the WAL record.
While at it, restructure the coding to ensure all page changes occur in
a single critical section without much room for failures. The previous
coding wasn't using a critical section, without any explanation as to
why this was acceptable.
In replication scenarios using the 9.3 branch, standby servers must be
upgraded before their master, so that they are prepared to deal with the
new WAL record once the master is upgraded; failure to do so will cause
WAL replay to die with a PANIC message. Later upgrade of the standby
will allow the process to continue where it left off, so there's no
disruption of the data in the standby in any case. Standbys know how to
deal with the old WAL record, so it's okay to keep the master running
the old code for a while.
In master, the old freeze WAL record is gone, for cleanliness' sake;
there's no compatibility concern there.
Backpatch to 9.3, where the original bug was introduced and where the
previous fix was backpatched.
Álvaro Herrera and Andres Freund
The original performs too poorly; in some scenarios it shows way too
high while profiling. Try to make it a bit smarter to avoid excessive
cosst. In particular, make it have a maximum size, and have entries be
sorted in LRU order; once the max size is reached, evict the oldest
entry to avoid it from growing too large.
Per complaint from Andres Freund in connection with new tuple freezing
code.
WAL records of hint bit updates is useful to tools that want to examine
which pages have been modified. In particular, this is required to make
the pg_rewind tool safe (without checksums).
This can also be used to test how much extra WAL-logging would occur if
you enabled checksums, without actually enabling them (which you can't
currently do without re-initdb'ing).
Sawada Masahiko, docs by Samrat Revagade. Reviewed by Dilip Kumar, with
further changes by me.
Set min_recovery_apply_delay to force a delay in recovery apply for commit and
restore point WAL records. Other records are replayed immediately. Delay is
measured between WAL record time and local standby time.
Robert Haas, Fabrízio de Royes Mello and Simon Riggs
Detailed review by Mitsumasa Kondo
When wal_level=logical, we'll log columns from the old tuple as
configured by the REPLICA IDENTITY facility added in commit
07cacba983. This makes it possible
a properly-configured logical replication solution to correctly
follow table updates even if they change the chosen key columns,
or, with REPLICA IDENTITY FULL, even if the table has no key at
all. Note that updates which do not modify the replica identity
column won't log anything extra, making the choice of a good key
(i.e. one that will rarely be changed) important to performance
when wal_level=logical is configured.
Each insert, update, or delete to a catalog table will also log
the CMIN and/or CMAX values of stamped by the current transaction.
This is necessary because logical decoding will require access to
historical snapshots of the catalog in order to decode some data
types, and the CMIN/CMAX values that we may need in order to judge
row visibility may have been overwritten by the time we need them.
Andres Freund, reviewed in various versions by myself, Heikki
Linnakangas, KONDO Mitsumasa, and many others.
When an external recovery command such as restore_command or
archive_cleanup_command fails, report the exit code properly,
distinguishing signals and normal exists, using the existing
wait_result_to_str() facility, instead of just reporting the return
value from system().
Reviewed-by: Peter Geoghegan <pg@heroku.com>
Both heap_freeze_tuple() and heap_tuple_needs_freeze() neglected to look
into a multixact to check the members against cutoff_xid. This means
that a very old Xid could survive hidden within a multi, possibly
outliving its CLOG storage. In the distant future, this would cause
clog lookup failures:
ERROR: could not access status of transaction 3883960912
DETAIL: Could not open file "pg_clog/0E78": No such file or directory.
This mostly was problematic when the updating transaction aborted, since
in that case the row wouldn't get pruned away earlier in vacuum and the
multixact could possibly survive for a long time. In many cases, data
that is inaccessible for this reason way can be brought back
heuristically.
As a second bug, heap_freeze_tuple() didn't properly handle multixacts
that need to be frozen according to cutoff_multi, but whose updater xid
is still alive. Instead of preserving the update Xid, it just set Xmax
invalid, which leads to both old and new tuple versions becoming
visible. This is pretty rare in practice, but a real threat
nonetheless. Existing corrupted rows, unfortunately, cannot be repaired
in an automated fashion.
Existing physical replicas might have already incorrectly frozen tuples
because of different behavior than in master, which might only become
apparent in the future once pg_multixact/ is truncated; it is
recommended that all clones be rebuilt after upgrading.
Following code analysis caused by bug report by J Smith in message
CADFUPgc5bmtv-yg9znxV-vcfkb+JPRqs7m2OesQXaM_4Z1JpdQ@mail.gmail.com
and privately by F-Secure.
Backpatch to 9.3, where freezing of MultiXactIds was introduced.
Analysis and patch by Andres Freund, with some tweaks by Álvaro.
Commit 9dc842f08 of 8.2 era prevented MultiXact truncation during crash
recovery, because there was no guarantee that enough state had been
setup, and because it wasn't deemed to be a good idea to remove data
during crash recovery anyway. Since then, due to Hot-Standby, streaming
replication and PITR, the amount of time a cluster can spend doing crash
recovery has increased significantly, to the point that a cluster may
even never come out of it. This has made not truncating the content of
pg_multixact/ not defensible anymore.
To fix, take care to setup enough state for multixact truncation before
crash recovery starts (easy since checkpoints contain the required
information), and move the current end-of-recovery actions to a new
TrimMultiXact() function, analogous to TrimCLOG().
At some later point, this should probably done similarly to the way
clog.c is doing it, which is to just WAL log truncations, but we can't
do that for the back branches.
Back-patch to 9.0. 8.4 also has the problem, but since there's no hot
standby there, it's much less pressing. In 9.2 and earlier, this patch
is simpler than in newer branches, because multixact access during
recovery isn't required. Add appropriate checks to make sure that's not
happening.
Andres Freund
While autovacuum dutifully launched anti-multixact-wraparound vacuums
when the multixact "age" was reached, the vacuum code was not aware that
it needed to make them be full table vacuums. As the resulting
partial-table vacuums aren't capable of actually increasing relminmxid,
autovacuum continued to launch anti-wraparound vacuums that didn't have
the intended effect, until age of relfrozenxid caused the vacuum to
finally be a full table one via vacuum_freeze_table_age.
To fix, introduce logic for multixacts similar to that for plain
TransactionIds, using the same GUCs.
Backpatch to 9.3, where permanent MultiXactIds were introduced.
Andres Freund, some cleanup by Álvaro
Parts of the code used autovacuum_freeze_max_age to determine whether
anti-multixact-wraparound vacuums are necessary, while others used a
hardcoded 200000000 value. This leads to problems when
autovacuum_freeze_max_age is set to a non-default value. Use the latter
everywhere.
Backpatch to 9.3, where vacuuming of multixacts was introduced.
Andres Freund
Prevent handle_sig_alarm from losing control partway through due to a query
cancel (either an asynchronous SIGINT, or a cancel triggered by one of the
timeout handler functions). That would at least result in failure to
schedule any required future interrupt, and might result in actual
corruption of timeout.c's data structures, if the interrupt happened while
we were updating those.
We could still lose control if an asynchronous SIGINT arrives just as the
function is entered. This wouldn't break any data structures, but it would
have the same effect as if the SIGALRM interrupt had been silently lost:
we'd not fire any currently-due handlers, nor schedule any new interrupt.
To forestall that scenario, forcibly reschedule any pending timer interrupt
during AbortTransaction and AbortSubTransaction. We can avoid any extra
kernel call in most cases by not doing that until we've allowed
LockErrorCleanup to kill the DEADLOCK_TIMEOUT and LOCK_TIMEOUT events.
Another hazard is that some platforms (at least Linux and *BSD) block a
signal before calling its handler and then unblock it on return. When we
longjmp out of the handler, the unblock doesn't happen, and the signal is
left blocked indefinitely. Again, we can fix that by forcibly unblocking
signals during AbortTransaction and AbortSubTransaction.
These latter two problems do not manifest when the longjmp reaches
postgres.c, because the error recovery code there kills all pending timeout
events anyway, and it uses sigsetjmp(..., 1) so that the appropriate signal
mask is restored. So errors thrown outside any transaction should be OK
already, and cleaning up in AbortTransaction and AbortSubTransaction should
be enough to fix these issues. (We're assuming that any code that catches
a query cancel error and doesn't re-throw it will do at least a
subtransaction abort to clean up; but that was pretty much required already
by other subsystems.)
Lastly, ProcSleep should not clear the LOCK_TIMEOUT indicator flag when
disabling that event: if a lock timeout interrupt happened after the lock
was granted, the ensuing query cancel is still going to happen at the next
CHECK_FOR_INTERRUPTS, and we want to report it as a lock timeout not a user
cancel.
Per reports from Dan Wood.
Back-patch to 9.3 where the new timeout handling infrastructure was
introduced. We may at some point decide to back-patch the signal
unblocking changes further, but I'll desist from that until we hear
actual field complaints about it.
Change SET LOCAL/CONSTRAINTS/TRANSACTION behavior outside of a
transaction block from error (post-9.3) to warning. (Was nothing in <=
9.3.) Also change ABORT outside of a transaction block from notice to
warning.
These bugs can cause data loss on standbys started with hot_standby=on at
the moment they start to accept read only queries, by marking committed
transactions as uncommited. The likelihood of such corruptions is small
unless the primary has a high transaction rate.
5a031a5556 fixed bugs in HS's startup logic
by maintaining less state until at least STANDBY_SNAPSHOT_PENDING state
was reached, missing the fact that both clog and subtrans are written to
before that. This only failed to fail in common cases because the usage
of ExtendCLOG in procarray.c was superflous since clog extensions are
actually WAL logged.
f44eedc3f0f347a856eea8590730769125964597/I then tried to fix the missing
extensions of pg_subtrans due to the former commit's changes - which are
not WAL logged - by performing the extensions when switching to a state
> STANDBY_INITIALIZED and not performing xid assignments before that -
again missing the fact that ExtendCLOG is unneccessary - but screwed up
twice: Once because latestObservedXid wasn't updated anymore in that
state due to the earlier commit and once by having an off-by-one error in
the loop performing extensions. This means that whenever a
CLOG_XACTS_PER_PAGE (32768 with default settings) boundary was crossed
between the start of the checkpoint recovery started from and the first
xl_running_xact record old transactions commit bits in pg_clog could be
overwritten if they started and committed in that window.
Fix this mess by not performing ExtendCLOG() in HS at all anymore since
it's unneeded and evidently dangerous and by performing subtrans
extensions even before reaching STANDBY_SNAPSHOT_PENDING.
Analysis and patch by Andres Freund. Reported by Christophe Pettus.
Backpatch down to 9.0, like the previous commit that caused this.
RecoveryIsInProgress() can be called very frequently. During normal
operation, it just checks a backend-local variable and returns quickly,
but during hot standby, it checks a spinlock-protected shared variable.
Those spinlock acquisitions can become a point of contention on a busy
hot standby system.
Replace the spinlock acquisition with a memory barrier.
Per discussion with Andres Freund, Ants Aasma and Merlin Moncure.
The TYPEALIGN macro, and the related ones like MAXALIGN, don't work with
values larger than intptr_t, because TYPEALIGN casts the argument to
intptr_t to do the arithmetic. That's not a problem when dealing with
pointers or lengths or offsets related to pointers, but the XLogInsert
scaling patch added a call to MAXALIGN with an XLogRecPtr argument.
To fix, add wider variants of the macros, called TYPEALIGN64 and MAXALIGN64,
which are just like the existing variants but work with uint64 instead of
intptr_t.
Report and patch by David Rowley, analysis by Andres Freund.
It seems to make more sense to use "cutoff multixact" terminology
throughout the backend code; "freeze" is associated with replacing of an
Xid with FrozenTransactionId, which is not what we do for MultiXactIds.
Andres Freund
Some adjustments by Álvaro Herrera
This reverts commit 269e780822
and commit 5b571bb8c8.
Unfortunately, the initial patch had insufficient performance testing,
and resulted in a regression.
Per report by Thom Brown.
Performance testing shows that if the insertpos_lck spinlock and the fields
that it protects are on the same cache line with other variables that are
frequently accessed, the false sharing can hurt performance a lot. Keep
them apart by adding some padding.
This keeps the usual trigger file name unchanged from 9.2, avoiding nasty
issues if you use a pre-9.3 pg_ctl binary with a 9.3 server or vice versa.
The fallback behavior of creating a full checkpoint before starting up is now
triggered by a file called "fallback_promote". That can be useful for
debugging purposes, but we don't expect any users to have to resort to that
and we might want to remove that in the future, which is why the fallback
mechanism is undocumented.
When upgrading from servers of versions 9.2 and older, and MultiXactIds
have been used in the old server beyond the first page (that is, 2048
multis or more in the default 8kB-page build), pg_upgrade would set the
next multixact offset to use beyond what has been allocated in the new
cluster. This would cause a failure the first time the new cluster
needs to use this value, because the pg_multixact/offsets/ file wouldn't
exist or wouldn't be large enough. To fix, ensure that the transient
server instances launched by pg_upgrade extend the file as necessary.
Per report from Jesse Denardo in
CANiVXAj4c88YqipsyFQPboqMudnjcNTdB3pqe8ReXqAFQ=HXyA@mail.gmail.com
Initialization of the first XLOG buffer at end-of-recovery was broken for
the case that the last read WAL record ended at a page boundary. Instead of
trying to copy the last full xlog page to the buffer cache in that case,
just set shared state so that the next page is initialized when the first
WAL record after startup is inserted. (that's what we did in earlier
version, too)
To make the shared state required for that case less surprising, replace the
XLogCtl->curridx variable, which was the index of the latest initialized
buffer, with an XLogRecPtr of how far the buffers have been initialized.
That also allows us to get rid of the XLogRecEndPtrToBufIdx macro.
While we're at it, make a similar change for XLogCtl->Write.curridx, getting
rid of that variable and calculating the next buffer to write from
XLogCtl->LogwrtResult instead.
Was broken by my xloginsert scaling patch. XLogCtl global variable needs
to be initialized in each process, as it's not inherited by fork() on
Windows.
This patch replaces WALInsertLock with a number of WAL insertion slots,
allowing multiple backends to insert WAL records to the WAL buffers
concurrently. This is particularly useful for parallel loading large amounts
of data on a system with many CPUs.
This has one user-visible change: switching to a new WAL segment with
pg_switch_xlog() now fills the remaining unused portion of the segment with
zeros. This potentially adds some overhead, but it has been a very common
practice by DBA's to clear the "tail" of the segment with an external
pg_clearxlogtail utility anyway, to make the WAL files compress better.
With this patch, it's no longer necessary to do that.
This patch adds a new GUC, xloginsert_slots, to tune the number of WAL
insertion slots. Performance testing suggests that the default, 8, works
pretty well for all kinds of worklods, but I left the GUC in place to allow
others with different hardware to test that easily. We might want to remove
that before release.
Reviewed by Andres Freund.
On some platforms, posix_fallocate() is available but may still return
EINVAL if the underlying filesystem does not support it. So, in case
of an error, fall through to the alternate implementation that just
writes zeros.
Per buildfarm failure and analysis by Tom Lane.
This function is more efficient than actually writing out zeroes to
the new file, per microbenchmarks by Jon Nelson. Also, it may reduce
the likelihood of WAL file fragmentation.
Jon Nelson, with review by Andres Freund, Greg Smith and me.
In 9.3, there's no particular limit on the number of bgworkers;
instead, we just count up the number that are actually registered,
and use that to set MaxBackends. However, that approach causes
problems for Hot Standby, which needs both MaxBackends and the
size of the lock table to be the same on the standby as on the
master, yet it may not be desirable to run the same bgworkers in
both places. 9.3 handles that by failing to notice the problem,
which will probably work fine in nearly all cases anyway, but is
not theoretically sound.
A further problem with simply counting the number of registered
workers is that new workers can't be registered without a
postmaster restart. This is inconvenient for administrators,
since bouncing the postmaster causes an interruption of service.
Moreover, there are a number of applications for background
processes where, by necessity, the background process must be
started on the fly (e.g. parallel query). While this patch
doesn't actually make it possible to register new background
workers after startup time, it's a necessary prerequisite.
Patch by me. Review by Michael Paquier.
We don't normally bother retrying when the number of bytes written by
write() is short of what was requested. It is generally assumed that a
write() to disk doesn't return short, unless you run out of disk space.
While writing the WAL, however, it seems prudent to try a bit harder,
because a failure leads to PANIC. The write() is also much larger than most
write()s in the backend (up to wal_buffers), so there's more room for
surprises.
Also retry on EINTR. All signals used in the backend are flagged SA_RESTART
nowadays, so it shouldn't happen, but better to be defensive.
In some cases with higher numbers of subtransactions
it was possible for us to incorrectly initialize
subtrans leading to complaints of missing pages.
Bug report by Sergey Konoplev
Analysis and fix by Andres Freund
Most of the documentation uses "single-user mode", so use that in the
code as well. Adjust the documentation to match the new error message
wording. Also add a documentation index entry for "single-user mode".
Based-on-patch-by: Jeff Janes <jeff.janes@gmail.com>
MarkBufferDirtyHint() writes WAL, and should know if it's got a
standard buffer or not. Currently, the only callers where buffer_std
is false are related to the FSM.
In passing, rename XLOG_HINT to XLOG_FPI, which is more descriptive.
Back-patch to 9.3.
elog.c has historically treated LOG messages as low-priority during
bootstrap and standalone operation. This has led to confusion and even
masked a bug, because the normal expectation of code authors is that
elog(LOG) will put something into the postmaster log, and that wasn't
happening during initdb. So get rid of the special-case rule and make
the priority order the same as it is in normal operation. To keep from
cluttering initdb's output and the behavior of a standalone backend,
tweak the severity level of three messages routinely issued by xlog.c
during startup and shutdown so that they won't appear in these cases.
Per my proposal back in December.
Since commit f21bb9cfb5, this function
ignores the caller-provided length and loops until it finds a
terminator, which GetVirtualXIDsDelayingChkpt() never adds. Restore the
previous loop control logic. In passing, revert the addition of an
unused variable by the same commit, presumably a debugging relic.
Seems cleaner to get the currently-replayed TLI in the same call to
GetXLogReplayRecPtr that we get the WAL position. Make it more clear in the
comment what the code does when recovery has already ended
(RecoveryInProgress() will set ThisTimeLineID in that case). Finally, make
resetting ThisTimeLineID afterwards more explicit.
Make slightly better decisions about indentation than what pgindent
is capable of. Mostly breaking out long function calls into one
line per argument, with a few other minor adjustments.
No functional changes- all whitespace.
pgindent ran cleanly (didn't change anything) after.
Passes all regressions.
checkpointer needs to reset ThisTimeLineID after
a restartpoint to allow installing/recycling new
WAL files. If recovery has already ended this
would leave ThisTimeLineID set incorrectly and
so we must reset it otherwise later checkpoints
do not have the correct timeline.
Bug report by Heikki Linnakangas.
Further investigation by Heikki and myself.
This simplifies the handling of crashes after fast promotion and various
minor cases that can exist in short timing windows around that case.
Broad fix to bug reported by Michael Paquier on -hackers,
approach prompted by Heikki Linnakangas
If OID wraparound should occur while in standalone mode (unlikely but
possible), we want to advance the counter to FirstNormalObjectId not
FirstBootstrapObjectId. Otherwise, user objects might be created with OIDs
in the system-reserved range. That isn't immediately harmful but it poses
a risk of conflicts during future pg_upgrade operations.
Noted by Andres Freund. Back-patch to all supported branches, since all of
them are supported sources for pg_upgrade operations.
If a standby server has a cascading standby server connected to it, it's
possible that WAL has already been sent up to the next WAL page boundary,
splitting a WAL record in the middle, when the first standby server is
promoted. Don't throw an assertion failure or error in walsender if that
happens.
Also, fix a variant of the same bug in pg_receivexlog: if it had already
received WAL on previous timeline up to a segment boundary, when the
upstream standby server is promoted so that the timeline switch record falls
on the previous segment, pg_receivexlog would miss the segment containing
the timeline switch. To fix that, have walsender send the position of the
timeline switch at end-of-streaming, in addition to the next timeline's ID.
It was previously assumed that the switch happened exactly where the
streaming stopped.
Note: this is an incompatible change in the streaming protocol. You might
get an error if you try to stream over timeline switches, if the client is
running 9.3beta1 and the server is more recent. It should be fine after a
reconnect, however.
Reported by Fujii Masao.
Heikki reported comment was wrong, so fixed
code to match the comment: we only need to
take additional locking precautions when we
have a shared lock on the buffer.
We copy the buffer before inserting an XLOG_HINT to avoid WAL CRC errors
caused by concurrent hint writes to buffer while share locked. To make this work
we refactor RestoreBackupBlock() to allow an XLOG_HINT to avoid the normal
path for backup blocks, which assumes the underlying buffer is exclusive locked.
Resulting code completely changes layout of XLOG_HINT WAL records, but
this isn't even beta code, so this is a low impact change.
In passing, avoid taking WALInsertLock for full page writes on checksummed
hints, remove related cruft from XLogInsert() and improve xlog_desc record for
XLOG_HINT.
Andres Freund
Bug report by Fujii Masao, testing by Jeff Janes and Jaime Casanova,
review by Jeff Davis and Simon Riggs. Applied with changes from review
and some comment editing.
The pg_start_backup() and pg_stop_backup() functions checked the privileges
of the initially-authenticated user rather than the current user, which is
wrong. For example, a user-defined index function could successfully call
these functions when executed by ANALYZE within autovacuum. This could
allow an attacker with valid but low-privilege database access to interfere
with creation of routine backups. Reported and fixed by Noah Misch.
Security: CVE-2013-1901
Checksums are set immediately prior to flush out of shared buffers
and checked when pages are read in again. Hint bit setting will
require full page write when block is dirtied, which causes various
infrastructure changes. Extensive comments, docs and README.
WARNING message thrown if checksum fails on non-all zeroes page;
ERROR thrown but can be disabled with ignore_checksum_failure = on.
Feature enabled by an initdb option, since transition from option off
to option on is long and complex and has not yet been implemented.
Default is not to use checksums.
Checksum used is WAL CRC-32 truncated to 16-bits.
Simon Riggs, Jeff Davis, Greg Smith
Wide input and assistance from many community members. Thank you.
Remove use of PageSetTLI() from all page manipulation functions
and adjust README to indicate change in the way we make changes
to pages. Repurpose those bytes into the pd_checksum field and
explain how that works in comments about page header.
Refactoring ahead of actual feature patch which would make use
of the checksum field, arriving later.
Jeff Davis, with comments and doc changes by Simon Riggs
Direction suggested by Robert Haas; many others providing
review comments.
We had two copies of this function in the backend and libpq, which was
already pretty bogus, but it turns out that we need it in some other
programs that don't use libpq (such as pg_test_fsync). So put it where
it probably should have been all along. The signal-mask-initialization
support in src/backend/libpq/pqsignal.c stays where it is, though, since
we only need that in the backend.
If we were about to enter archive recovery after crash recovery, we scanned
the archive for the latest tli history file, and set the recovery target
timeline to that. However, when we actually tried to read the history file,
we would not fetch the file from the archive, because we were not in archive
recovery yet.
To fix, make readTimeLineHistory and existsTimeLineHistory to always fetch
the file from archive if archive recovery is requested, even if we're not in
archive recovery yet.
Backpatch to 9.2. Mitsumasa KONDO
fmgr_sql had been designed on the assumption that the FmgrInfo it's called
with has only query lifespan. This is demonstrably unsafe in connection
with range types, as shown in bug #7881 from Andrew Gierth. Fix things
so that we re-generate the function's cache data if the (sub)transaction
it was made in is no longer active.
Back-patch to 9.2. This might be needed further back, but it's not clear
whether the case can realistically arise without range types, so for now
I'll desist from back-patching further.
We must still initialize minRecoveryPoint if we start straight with archive
recovery, e.g when recovering from a normal base backup taken with
pg_start/stop_backup. Otherwise we never consider the system consistent.
If you create a base backup using an atomic filesystem snapshot, and try to
perform PITR starting from that base backup, or if you just kill a master
server and create recovery.conf to put it into standby mode, we don't know
how far we need to recover before reaching consistency. Normally in crash
recovery, we replay all the WAL present in pg_xlog, and assume that we're
consistent after that. And normally in archive recovery, minRecoveryPoint,
backupEndRequired, or backupEndPoint is set in the control file, indicating
how far we need to replay to reach consistency. But if the server was
previously up and running normally, and you kill -9 it or take an atomic
filesystem snapshot, none of those fields are set in the control file.
The solution is to perform crash recovery first, replaying all the WAL in
pg_xlog. After that's done, we assume that the system is consistent like in
normal crash recovery, and switch to archive recovery mode after that.
Per report from Kyotaro HORIGUCHI. In his scenario, recovery.conf was
created after "pg_ctl stop -m i". I'm not sure we need to support that exact
scenario, but we should support backing up using a filesystem snapshot,
which looks identical.
This issue goes back to at least 9.0, where hot standby was introduced and
we started to track when consistency is reached. In 9.1 and 9.2, we would
open up for hot standby too early, and queries could briefly see an
inconsistent state. But 9.2 made it more visible, as we started to PANIC if
we see a reference to a non-existing page during recovery, if we've already
reached consistency. This is a fairly big patch, so back-patch to 9.2 only,
where the issue is more visible. We can consider back-patching further after
this has received some more testing in 9.2 and master.
This enables non-backend code, such as pg_xlogdump, to use it easily.
The previous location, in src/backend/catalog/catalog.c, made that
essentially impossible because that file depends on many backend-only
facilities; so this needs to live separately.
Revert my earlier fix for the bug that unarchived WAL files get deleted on
crash recovery, commit c9cc7e05c6. We create
a .done file for files streamed or restored from archive, so the WAL file
recycling logic used during normal operation works just as well during
archive recovery.
Per Fujii Masao's suggestion.
This is a forward-patch of commit 6f4b8a4f4f,
applied to 9.2 back in August. The plan was to do something else in master,
but it looks like it's not going to happen, so let's just apply the 9.2
solution to master as well.
Fujii Masao
Currently it's only possible for loadable modules to get control during
post-commit cleanup of a transaction. That doesn't work too well if they
want to do something that could throw an error; for example, an FDW might
need to issue a remote commit, which could well fail. To improve matters,
extend the existing APIs for XactCallback and SubXactCallback functions
to provide new pre-commit events for this purpose.
The release notes will need to mention that existing callback functions
should be checked to make sure they don't do something unwanted when one
of the new event types occurs. In the examples within our source tree,
contrib/sepgsql was fine but plpgsql had been a bit too cute.
The reason this wasn't supported before was that GiST indexes need an
increasing sequence to detect concurrent page-splits. In a regular WAL-
logged GiST index, the LSN of the page-split record is used for that
purpose, and in a temporary index, we can get away with a backend-local
counter. Neither of those methods works for an unlogged relation.
To provide such an increasing sequence of numbers, create a "fake LSN"
counter that is saved and restored across shutdowns. On recovery, unlogged
relations are blown away, so the counter doesn't need to survive that
either.
Jeevan Chalke, based on discussions with Robert Haas, Tom Lane and me.
The intention was to request a regular online checkpoint immediately after
end of recovery, when performing "fast promotion". However, because the
checkpoint was requested before other backends were allowed to write WAL,
the checkpointer process performed a restartpoint rather than a checkpoint.
Delay the RequestCheckPoint call until after recovery has truly ended, so
that you get a real checkpoint.
This isn't used for anything but a sanity check at the moment, but it could
be highly valuable for debugging purposes. It could also be used to recreate
timeline history by traversing WAL, which seems useful.
The new rmgrlist.h header, containing all necessary data
about built-in resource managers, allows other pieces of code to
access them.
In particular, this allows a future pg_xlogdump program to extract
rm_desc function pointers, without having to keep a duplicate list of
them.
Previous patch to skip checkpoints at end of recovery didn't
correctly perform crash recovery, fumbling the timeline switch.
Now we record the minRecoveryPointTLI of the newly selected
timeline, so that we crash recover to the correct timeline.
Bug report from Fujii Masao, investigated by me.
pg_ctl promote -m fast will skip the checkpoint at end of recovery so that we
can achieve very fast failover when the apply delay is low. Write new WAL record
XLOG_END_OF_RECOVERY to allow us to switch timeline correctly for downstream log
readers. If we skip synchronous end of recovery checkpoint we request a normal
spread checkpoint so that the window of re-recovery is low.
Simon Riggs and Kyotaro Horiguchi, with input from Fujii Masao.
Review by Heikki Linnakangas
This patch introduces two additional lock modes for tuples: "SELECT FOR
KEY SHARE" and "SELECT FOR NO KEY UPDATE". These don't block each
other, in contrast with already existing "SELECT FOR SHARE" and "SELECT
FOR UPDATE". UPDATE commands that do not modify the values stored in
the columns that are part of the key of the tuple now grab a SELECT FOR
NO KEY UPDATE lock on the tuple, allowing them to proceed concurrently
with tuple locks of the FOR KEY SHARE variety.
Foreign key triggers now use FOR KEY SHARE instead of FOR SHARE; this
means the concurrency improvement applies to them, which is the whole
point of this patch.
The added tuple lock semantics require some rejiggering of the multixact
module, so that the locking level that each transaction is holding can
be stored alongside its Xid. Also, multixacts now need to persist
across server restarts and crashes, because they can now represent not
only tuple locks, but also tuple updates. This means we need more
careful tracking of lifetime of pg_multixact SLRU files; since they now
persist longer, we require more infrastructure to figure out when they
can be removed. pg_upgrade also needs to be careful to copy
pg_multixact files over from the old server to the new, or at least part
of multixact.c state, depending on the versions of the old and new
servers.
Tuple time qualification rules (HeapTupleSatisfies routines) need to be
careful not to consider tuples with the "is multi" infomask bit set as
being only locked; they might need to look up MultiXact values (i.e.
possibly do pg_multixact I/O) to find out the Xid that updated a tuple,
whereas they previously were assured to only use information readily
available from the tuple header. This is considered acceptable, because
the extra I/O would involve cases that would previously cause some
commands to block waiting for concurrent transactions to finish.
Another important change is the fact that locking tuples that have
previously been updated causes the future versions to be marked as
locked, too; this is essential for correctness of foreign key checks.
This causes additional WAL-logging, also (there was previously a single
WAL record for a locked tuple; now there are as many as updated copies
of the tuple there exist.)
With all this in place, contention related to tuples being checked by
foreign key rules should be much reduced.
As a bonus, the old behavior that a subtransaction grabbing a stronger
tuple lock than the parent (sub)transaction held on a given tuple and
later aborting caused the weaker lock to be lost, has been fixed.
Many new spec files were added for isolation tester framework, to ensure
overall behavior is sane. There's probably room for several more tests.
There were several reviewers of this patch; in particular, Noah Misch
and Andres Freund spent considerable time in it. Original idea for the
patch came from Simon Riggs, after a problem report by Joel Jacobson.
Most code is from me, with contributions from Marti Raudsepp, Alexander
Shulgin, Noah Misch and Andres Freund.
This patch was discussed in several pgsql-hackers threads; the most
important start at the following message-ids:
AANLkTimo9XVcEzfiBR-ut3KVNDkjm2Vxh+t8kAmWjPuv@mail.gmail.com1290721684-sup-3951@alvh.no-ip.org1294953201-sup-2099@alvh.no-ip.org1320343602-sup-2290@alvh.no-ip.org1339690386-sup-8927@alvh.no-ip.org4FE5FF020200002500048A3D@gw.wicourts.gov4FEAB90A0200002500048B7D@gw.wicourts.gov
When a standby server follows the master using WAL archive, and it chooses
a new timeline (recovery_target_timeline='latest'), it only fetches the
timeline history file for the chosen target timeline, not any other history
files that might be missing from pg_xlog. For example, if the current
timeline is 2, and we choose 4 as the new recovery target timeline, the
history file for timeline 3 is not fetched, even if it's part of this
server's history. That's enough for the standby itself - the history file
for timeline 4 includes timeline 3 as well - but if a cascading standby
server wants to recover to timeline 3, it needs the history file. To fix,
when a new recovery target timeline is chosen, try to copy any missing
history files from the archive to pg_xlog between the old and new target
timeline.
A second similar issue was with the WAL files. When a standby recovers from
archive, and it reaches a segment that contains a switch to a new timeline,
recovery fetches only the WAL file labelled with the new timeline's ID. The
file from the new timeline contains a copy of the WAL from the old timeline
up to the point where the switch happened, and recovery recovers it from the
new file. But in streaming replication, walsender only tries to read it
from the old timeline's file. To fix, change walsender to read it from the
new file, so that it behaves the same as recovery in that sense, and doesn't
try to open the possibly nonexistent file with the old timeline's ID.
The xlogreader refactoring broke the logic to decide which timeline to start
streaming from. XLogPageRead() uses the timeline history to check which
timeline the requested WAL position falls into. However, after the
refactoring, XLogPageRead() is always first called with the first page in
the segment, to verify the segment header, and only then with the actual WAL
position we're interested in. That first read of the segment's header made
XLogPageRead() to always start streaming from the old timeline containing
the segment header, not the timeline containing the actual record, if there
was a timeline switch within the segment.
I thought I fixed this yesterday, but that fix was too narrow and only fixed
this for the corner-case that the timeline switch happened in the first page
of the segment. To fix this more robustly, pass explicitly the position of
the record we're actually interested in to XLogPageRead, and use that to
decide which timeline to read from, rather than deduce it from the page and
offset.
Per report from Fujii Masao.
get a large enough part of the page to include the beginning of the next
record we're interested in. The XLogPageRead callback uses the requested
length to decide which timeline to stream WAL from, and if the first call
is short, and the page contains a timeline switch, we'll repeatedly try
to stream that page from the old timeline, and never get across the
timeline switch.
This mirrors the changes done earlier to the server in standby mode. When
receivelog reaches the end of a timeline, as reported by the server, it
fetches the timeline history file of the next timeline, and restarts
streaming from the new timeline by issuing a new START_STREAMING command.
When pg_receivexlog crosses a timeline, it leaves the .partial suffix on the
last segment on the old timeline. This helps you to tell apart a partial
segment left in the directory because of a timeline switch, and a completed
segment. If you just follow a single server, it won't make a difference, but
it can be significant in more complicated scenarios where new WAL is still
generated on the old timeline.
This includes two small changes to the streaming replication protocol:
First, when you reach the end of timeline while streaming, the server now
sends the TLI of the next timeline in the server's history to the client.
pg_receivexlog uses that as the next timeline, so that it doesn't need to
parse the timeline history file like a standby server does. Second, when
BASE_BACKUP command sends the begin and end WAL positions, it now also sends
the timeline IDs corresponding the positions.
XLogReadRecord should reset its state on every error, to make sure it
re-reads the page on next call. It was inconsistent in that some errors did
that, but some did not.
In ReadRecord(), don't give up on an error if we're in standby mode. The
loop was set up to retry, but the checks within the loop broke out of the
loop on any error.
Andres Freund, with some tweaking by me.
This new facility can not only be used by xlog.c to carry out crash
recovery, but also by external programs. By supplying a function to
read XLog pages from somewhere, all the WAL reading can be used for
completely different purposes.
For the standard backend use, the behavior should be pretty much the
same as previously. As for non-backend programs, an hypothetical
pg_xlogdump program is now closer to reality, but some more backend
support is still necessary.
This patch was originally submitted by Andres Freund in a different
form, but Heikki Linnakangas opted for and authored another design of
the concept. Andres has advanced the patch since Heikki's initial
version. Review and some (mostly cosmetics) changes by me.
If you take a base backup from a standby server with "pg_basebackup -X
fetch", and the timeline switches while the backup is being taken, the
backup used to fail with an error "requested WAL segment %s has already
been removed". This is because the server-side code that sends over the
required WAL files would not construct the WAL filename with the correct
timeline after a switch.
Fix that by using readdir() to scan pg_xlog for all the WAL segments in the
range, regardless of timeline.
Also, include all timeline history files in the backup, if taken with
"-X fetch". That fixes another related bug: If a timeline switch happened
just before the backup was initiated in a standby, the WAL segment
containing the initial checkpoint record contains WAL from the older
timeline too. Recovery will not accept that without a timeline history file
that lists the older timeline.
Backpatch to 9.2. Versions prior to that were not affected as you could not
take a base backup from a standby before 9.2.
Streaming replication can fetch any missing timeline history files from the
master, but recovery would read the timeline history file for the target
timeline before reading the checkpoint record, and before walreceiver has
had a chance to fetch it from the master. Delay reading it, and the sanity
checks involving timeline history, until after reading the checkpoint
record.
There is at least one scenario where this makes a difference: if you take
a base backup from a standby server right after a timeline switch, the
WAL segment containing the initial checkpoint record will begin with an
older timeline ID. Without the timeline history file, recovering that file
will fail as the older timeline ID is not recognized to be an ancestor of
the target timeline. If you try to recover from such a backup, using only
streaming replication to fetch the WAL, this patch is required for that to
work.
After receiving some WAL over streaming replication, try to open the file
from the timeline we're currently recieving, not recoveryTargetTLI. They
are usually the same, which is why wasn't noticed before, but you'd get
an error if there have been more than one timeline switch between the
current point in WAL and the recovery target.
The cascading standby patch in 9.2 changed the way WAL files are treated
when restored from the archive. Before, they were restored under a temporary
filename, and not kept in pg_xlog, but after the patch, they were copied
under pg_xlog. This is necessary for a cascading standby to find them, but
it also means that if the archive goes offline and a standby is restarted,
it can recover back to where it was using the files in pg_xlog. It also
means that if you take an offline backup from a standby server, it includes
all the required WAL files in pg_xlog.
However, the same change was not made to timeline history files, so if the
WAL segment containing the checkpoint record contains a timeline switch, you
will still get an error if you try to restart recovery without the archive,
or recover from an offline backup taken from the standby.
With this patch, timeline history files restored from archive are copied
into pg_xlog like WAL files are, so that pg_xlog contains all the files
required to recover. This is a corner-case pre-existing issue in 9.2, but
even more important in master where it's possible for a standby to follow a
timeline switch through streaming replication. To make that possible, the
timeline history files must be present in pg_xlog.
This gets rid of XLByteLT, XLByteLE, XLByteEQ and XLByteAdvance.
These were useful for brevity when XLogRecPtrs were split in
xlogid/xrecoff; but now that they are simple uint64's, they are just
clutter. The only downside to making this change would be ease of
backporting patches, but that has been negated by other substantive
changes to the involved code anyway. The clarity of simpler expressions
makes the change worthwhile.
Most of the changes are mechanical, but in a couple of places, the patch
author chose to invert the operator sense, making the code flow more
logical (and more in line with preceding comments).
Author: Andres Freund
Eyeballed by Dimitri Fontaine and Alvaro Herrera
This was broken before, we would recycle old WAL segments on wrong timeline
after the recovery target timeline had changed, but my recent commit to
not initialize ThisTimeLineID at all in a standby's checkpointer process
broke this completely.
The problem is that when installing a recycled WAL segment as a future one,
ThisTimeLineID is used to construct the filename. To fix, always update
ThisTimeLineID to the current timeline being recovered, before recycling
WAL segments at a restartpoint.
This still leaves a small window where we might install WAL segments under
wrong timeline ID, if the timeline is changed just as we're about to start
recycling. Also, even if we're replaying timeline X at the momnent, there's
no guarantee that we'll need as many WAL segments on that timeline as we
recycle. We might be just about to reach the point where we switch to next
timeline, so might only need one more WAL segment on the current timeline.
We'll live with the waste in that situation.
Bug pointed out by Fujii Masao. 9.1 and 9.2 had the same issue, when
recovery target timeline was changed, but I committed a slightly different
version of this patch on those branches.
Most of the time, the last replayed record comes from the recovery target
timeline, but there is a corner case where it makes a difference. When
the startup process scans for a new timeline, and decides to change recovery
target timeline, there is a window where the recovery target TLI has already
been bumped, but there are no WAL segments from the new timeline in pg_xlog
yet. For example, if we have just replayed up to point 0/30002D8, on
timeline 1, there is a WAL file called 000000010000000000000003 in pg_xlog
that contains the WAL up to that point. When recovery switches recovery
target timeline to 2, a walsender can immediately try to read WAL from
0/30002D8, from timeline 2, so it will try to open WAL file
000000020000000000000003. However, that doesn't exist yet - the startup
process hasn't copied that file from the archive yet nor has the walreceiver
streamed it yet, so walsender fails with error "requested WAL segment
000000020000000000000003 has already been removed". That's harmless, in that
the standby will try to reconnect later and by that time the segment is
already created, but error messages that should be ignored are not good.
To fix that, have walsender track the TLI of the last replayed record,
instead of the recovery target timeline. That way walsender will not try to
read anything from timeline 2, until the WAL segment has been created and at
least one record has been replayed from it. The recovery target timeline is
now xlog.c's internal affair, it doesn't need to be exposed in shared memory
anymore.
This fixes the error reported by Thom Brown. depesz the same error message,
but I'm not sure if this fixes his scenario.
We used to set it to the current recovery target timeline, but the recovery
target timeline can change during recovery, leaving ThisTimeLineID at an
old value. That seems worse than always leaving it at zero to begin with.
AFAICS there was no good reason to set it in the first place. ThisTimeLineID
is not needed in checkpointer or bgwriter process, until it's time to write
the end-of-recovery checkpoint, and at that point ThisTimeLineID is updated
anyway.
If you restored from a backup taken from a standby, and the last record in
the backup is the checkpoint record, ie. there is no redo required except
for the checkpoint record, we would fail to notice that we've reached the
end-of-backup point, and the database is consistent. The result was an
error "WAL ends before end of online backup". To fix, move the
have-we-reached-end-of-backup check into CheckRecoveryConsistency(), which
is already responsible for similar checks with minRecoveryPoint, and is
called in the right places.
Backpatch to 9.2, this check and bug did not exist before that.
Before this patch, streaming replication would refuse to start replicating
if the timeline in the primary doesn't exactly match the standby. The
situation where it doesn't match is when you have a master, and two
standbys, and you promote one of the standbys to become new master.
Promoting bumps up the timeline ID, and after that bump, the other standby
would refuse to continue.
There's significantly more timeline related logic in streaming replication
now. First of all, when a standby connects to primary, it will ask the
primary for any timeline history files that are missing from the standby.
The missing files are sent using a new replication command TIMELINE_HISTORY,
and stored in standby's pg_xlog directory. Using the timeline history files,
the standby can follow the latest timeline present in the primary
(recovery_target_timeline='latest'), just as it can follow new timelines
appearing in an archive directory.
START_REPLICATION now takes a TIMELINE parameter, to specify exactly which
timeline to stream WAL from. This allows the standby to request the primary
to send over WAL that precedes the promotion. The replication protocol is
changed slightly (in a backwards-compatible way although there's little hope
of streaming replication working across major versions anyway), to allow
replication to stop when the end of timeline reached, putting the walsender
back into accepting a replication command.
Many thanks to Amit Kapila for testing and reviewing various versions of
this patch.
EndRecPtr is the last record that we've read, but not necessarily yet
replayed. CheckRecoveryConsistency should compare minRecoveryPoint with the
last replayed record instead. This caused recovery to think it's reached
consistency too early.
Now that we do the check in CheckRecoveryConsistency correctly, we have to
move the call of that function to after redoing a record. The current place,
after reading a record but before replaying it, is wrong. In particular, if
there are no more records after the one ending at minRecoveryPoint, we don't
enter hot standby until one extra record is generated and read by the
standby, and CheckRecoveryConsistency is called. These two bugs conspired
to make the code appear to work correctly, except for the small window
between reading the last record that reaches minRecoveryPoint, and
replaying it.
In the passing, rename recoveryLastRecPtr, which is the last record
replayed, to lastReplayedEndRecPtr. This makes it slightly less confusing
with replayEndRecPtr, which is the last record read that we're about to
replay.
Original report from Kyotaro HORIGUCHI, further diagnosis by Fujii Masao.
Backpatch to 9.0, where Hot Standby subtly changed the test from
"minRecoveryPoint < EndRecPtr" to "minRecoveryPoint <= EndRecPtr". The
former works because where the test is performed, we have always read one
more record than we've replayed.
If a file is truncated, we must update minRecoveryPoint. Once a file is
truncated, there's no going back; it would not be safe to stop recovery
at a point earlier than that anymore.
Per report from Kyotaro HORIGUCHI. Backpatch to 8.4. Before that,
minRecoveryPoint was not updated during recovery at all.
Forgot to update it at the right place. Also, consider checkpoint record
that switches to new timelne to be on the new timeline.
This fixes erroneous "requested timeline 2 does not contain minimum recovery
point" errors, pointed out by Amit Kapila while testing another patch.
If we're not in hot standby mode, then there's no way for users to connect
to reset the recoveryPause flag, so we shouldn't pause. The code was aware
of this but the test to see if pausing was safe was seriously inadequate:
it wasn't paying attention to reachedConsistency, and besides what it was
testing was that we could legally enter hot standby, not that we have
done so. Get rid of that in favor of checking LocalHotStandbyActive,
which because of the coding in CheckRecoveryConsistency is tantamount to
checking that we have told the postmaster to enter hot standby.
Also, move the recoveryPausesHere() call that reacts to asynchronous
recoveryPause requests so that it's not in the middle of application of a
WAL record. I put it next to the recoveryStopsHere() call --- in future
those are going to need to interact significantly, so this seems like a
good waystation.
Also, don't bother trying to read another WAL record if we've already
decided not to continue recovery. This was no big deal when the code was
written originally, but now that reading a record might entail actions like
fetching an archive file, it seems a bit silly to do it like that.
Per report from Jeff Janes and subsequent discussion. The pause feature
needs quite a lot more work, but this gets rid of some indisputable bugs,
and seems safe enough to back-patch.
When waiting for an XLOG_BACKUP_RECORD the minRecoveryPoint
will be incorrect, so we must not declare recovery as consistent
before we have seen the record. Major bug allowing recovery to end
too early in some cases, allowing people to see inconsistent db.
This patch to HEAD and 9.2, other fix required for 9.1 and 9.0
Simon Riggs and Andres Freund, bug report by Jeff Janes
This allows us to do some more rigorous sanity checking for various
incorrect point-in-time recovery scenarios, and provides more information
for debugging purposes. It will also come handy in the upcoming patch to
allow timeline switches to be replicated by streaming replication.
This allows recovery to notice certain incorrect recovery scenarios.
If a server has recovered to point X on timeline 5, and you restart
recovery, it better be on timeline 5 when it reaches point X again, not on
some timeline with a higher ID. This can happen e.g if you a standby server
is shut down, a new timeline appears in the WAL archive, and the standby
server is restarted. It will try to follow the new timeline, which is wrong
because some WAL on the old timeline was already replayed before shutdown.
Requires an initdb (or at least pg_resetxlog), because this adds a field to
the control file.
Rename PGXACT->inCommit flag into delayChkpt flag,
and generalise comments to allow use in other situations,
such as the forthcoming potential use in checksum patch.
Replace wait loop to look for VXIDs with delayChkpt set.
No user visible changes, not behaviour changes at present.
Simon Riggs, reviewed and rebased by Jeff Davis
Update README to explain prerequisites for
correct access to LSN fields of a page.
Independent chunk removed from checksums
patch to reduce size of patch.
This reverts commit c11130690d in favor of
actually fixing the problem: namely, that we should never have been
modifying the checkpoint record's nextXid at this point to begin with.
The nextXid should match the state as of the checkpoint's logical WAL
position (ie the redo point), not the state as of its physical position.
It's especially bogus to advance it in some wal_levels and not others.
In any case there is no need for the checkpoint record to carry the
same nextXid shown in the XLOG_RUNNING_XACTS record just emitted by
LogStandbySnapshot, as any replay operation will already have adopted
that value as current.
This fixes bug #7710 from Tarvi Pillessaar, and probably also explains bug
#6291 from Daniel Farina, in that if a checkpoint were in progress at the
instant of XID wraparound, the epoch bump would be lost as reported.
(And, of course, these days there's at least a 50-50 chance of a checkpoint
being in progress at any given instant.)
Diagnosed by me and independently by Andres Freund. Back-patch to all
branches supporting hot standby.
Previously we stored all xids mixed together.
Now we store top-level xids first, followed
by all subxids. Also skip logging any subxids
if the snapshot is suboverflowed, since there
are potentially large numbers of them and they
are not useful in that case anyway. Has value
in the envisaged design for decoding of WAL.
No planned effect on Hot Standby.
Andres Freund, reviewed by me
If wal_level = hot_standby we update the checkpoint nextxid,
though in the case where a wraparound occurred half-way through
a checkpoint we would neglect updating the epoch also. Updating
the nextxid is arguably the wrong thing to do, but changing that
may introduce subtle bugs into hot standby startup, while updating
the value doesn't cause any known bugs yet. Minimal fix now to
HEAD and backbranches, wider fix later in HEAD.
Bug reported in #6291 by Daniel Farina and slightly differently in
Cause analysis and recommended fixes from Tom Lane and Andres Freund.
Applied patch is minimal version of Andres Freund's work.
This was apparently a typo, which caused recovery to think that it
immediately reached the end of backup, and allowed the database to start
up too early.
Reported by Jeff Janes. Backpatch to 9.2, where this code was introduced.
Files opened with BasicOpenFile or PathNameOpenFile are not automatically
cleaned up on error. That puts unnecessary burden on callers that only want
to keep the file open for a short time. There is AllocateFile, but that
returns a buffered FILE * stream, which in many cases is not the nicest API
to work with. So add function called OpenTransientFile, which returns a
unbuffered fd that's cleaned up like the FILE* returned by AllocateFile().
This plugs a few rare fd leaks in error cases:
1. copy_file() - fixed by by using OpenTransientFile instead of BasicOpenFile
2. XLogFileInit() - fixed by adding close() calls to the error cases. Can't
use OpenTransientFile here because the fd is supposed to persist over
transaction boundaries.
3. lo_import/lo_export - fixed by using OpenTransientFile instead of
PathNameOpenFile.
In addition to plugging those leaks, this replaces many BasicOpenFile() calls
with OpenTransientFile() that were not leaking, because the code meticulously
closed the file on error. That wasn't strictly necessary, but IMHO it's good
for robustness.
The same leaks exist in older versions, but given the rarity of the issues,
I'm not backpatching this. Not yet, anyway - it might be good to backpatch
later, after this mechanism has had some more testing in master branch.
When startup process opens a WAL segment after replaying part of it, it
validates the first page on the WAL segment, even though the page it's
really interested in later in the file. As part of the validation, it checks
that the TLI on the page header is >= the TLI it saw on the last page it
read. If the segment contains a timeline switch, and we have already
replayed it, and then re-open the WAL segment (because of streaming
replication got disconnected and reconnected, for example), the TLI check
will fail when the first page is validated. Fix that by relaxing the TLI
check when re-opening a WAL segment.
Backpatch to 9.0. Earlier versions had the same code, but before standby
mode was introduced in 9.0, recovery never tried to re-read a segment after
partially replaying it.
Reported by Amit Kapila, while testing a new feature.
When I moved ExecuteRecoveryCommand() from xlog.c to xlogarchive.c, I didn't
realize that it's called from the checkpoint process, not the startup
process. I tried to use InRedo variable to decide whether or not to attempt
cleaning up the archive (must not do so before we have read the initial
checkpoint record), but that variable is only valid within the startup
process.
Instead, let ExecuteRecoveryCommand() always clean up the archive, and add
an explicit argument to RestoreArchivedFile() to say whether that's allowed
or not. The caller knows better.
Reported by Erik Rijkers, diagnosis by Fujii Masao. Only 9.3devel is
affected.
At commit all standby locks are released
for the top-level transaction, so searching
for locks for each subtransaction is both
pointless and costly (N^2) in the presence
of many AccessExclusiveLocks.
Most of the replay functions for WAL record types that modify more than
one page failed to ensure that those pages were locked correctly to ensure
that concurrent queries could not see inconsistent page states. This is
a hangover from coding decisions made long before Hot Standby was added,
when it was hardly necessary to acquire buffer locks during WAL replay
at all, let alone hold them for carefully-chosen periods.
The key problem was that RestoreBkpBlocks was written to hold lock on each
page restored from a full-page image for only as long as it took to update
that page. This was guaranteed to break any WAL replay function in which
there was any update-ordering constraint between pages, because even if the
nominal order of the pages is the right one, any mixture of full-page and
non-full-page updates in the same record would result in out-of-order
updates. Moreover, it wouldn't work for situations where there's a
requirement to maintain lock on one page while updating another. Failure
to honor an update ordering constraint in this way is thought to be the
cause of bug #7648 from Daniel Farina: what seems to have happened there
is that a btree page being split was rewritten from a full-page image
before the new right sibling page was written, and because lock on the
original page was not maintained it was possible for hot standby queries to
try to traverse the page's right-link to the not-yet-existing sibling page.
To fix, get rid of RestoreBkpBlocks as such, and instead create a new
function RestoreBackupBlock that restores just one full-page image at a
time. This function can be invoked by WAL replay functions at the points
where they would otherwise perform non-full-page updates; in this way, the
physical order of page updates remains the same no matter which pages are
replaced by full-page images. We can then further adjust the logic in
individual replay functions if it is necessary to hold buffer locks
for overlapping periods. A side benefit is that we can simplify the
handling of concurrency conflict resolution by moving that code into the
record-type-specfic functions; there's no more need to contort the code
layout to keep conflict resolution in front of the RestoreBkpBlocks call.
In connection with that, standardize on zero-based numbering rather than
one-based numbering for referencing the full-page images. In HEAD, I
removed the macros XLR_BKP_BLOCK_1 through XLR_BKP_BLOCK_4. They are
still there in the header files in previous branches, but are no longer
used by the code.
In addition, fix some other bugs identified in the course of making these
changes:
spgRedoAddNode could fail to update the parent downlink at all, if the
parent tuple is in the same page as either the old or new split tuple and
we're not doing a full-page image: it would get fooled by the LSN having
been advanced already. This would result in permanent index corruption,
not just transient failure of concurrent queries.
Also, ginHeapTupleFastInsert's "merge lists" case failed to mark the old
tail page as a candidate for a full-page image; in the worst case this
could result in torn-page corruption.
heap_xlog_freeze() was inconsistent about using a cleanup lock or plain
exclusive lock: it did the former in the normal path but the latter for a
full-page image. A plain exclusive lock seems sufficient, so change to
that.
Also, remove gistRedoPageDeleteRecord(), which has been dead code since
VACUUM FULL was rewritten.
Back-patch to 9.0, where hot standby was introduced. Note however that 9.0
had a significantly different WAL-logging scheme for GIST index updates,
and it doesn't appear possible to make that scheme safe for concurrent hot
standby queries, because it can leave inconsistent states in the index even
between WAL records. Given the lack of complaints from the field, we won't
work too hard on fixing that branch.
errcontext() is typically used in an error context callback function, not
within an ereport() invocation like e.g errmsg and errdetail are. That means
that the message domain that the TEXTDOMAIN magic in ereport() determines
is not the right one for the errcontext() calls. The message domain needs to
be determined by the C file containing the errcontext() call, not the file
containing the ereport() call.
Fix by turning errcontext() into a macro that passes the TEXTDOMAIN to use
for the errcontext message. "errcontext" was used in a few places as a
variable or struct field name, I had to rename those out of the way, now
that errcontext is a macro.
We've had this problem all along, but this isn't doesn't seem worth
backporting. It's a fairly minor issue, and turning errcontext from a
function to a macro requires at least a recompile of any external code that
calls errcontext().
Commit dfda6eba (which changed segment numbers to use a single 64 bit
variable instead of log/seg) introduced a couple of bogus choices of
exactly which log segment number variable to use in each case.
This is currently pretty harmless; in one place, the bogus number was
only being used in an error message for a pretty unlikely condition
(failure to fsync a WAL segment file). In the other, it was using a
global variable instead of the local variable; but all callsites were
passing the value of the global variable anyway.
No need to backpatch because that commit is not on earlier branches.
If an SMgrRelation is not "owned" by a relcache entry, don't allow it to
live past transaction end. This design allows the same SMgrRelation to be
used for blind writes of multiple blocks during a transaction, but ensures
that we don't hold onto such an SMgrRelation indefinitely. Because an
SMgrRelation typically corresponds to open file descriptors at the fd.c
level, leaving it open when there's no corresponding relcache entry can
mean that we prevent the kernel from reclaiming deleted disk space.
(While CacheInvalidateSmgr messages usually fix that, there are cases
where they're not issued, such as DROP DATABASE. We might want to add
some more sinval messaging for that, but I'd be inclined to keep this
type of logic anyway, since allowing VFDs to accumulate indefinitely
for blind-written relations doesn't seem like a good idea.)
This code replaces a previous attempt towards the same goal that proved
to be unreliable. Back-patch to 9.1 where the previous patch was added.
This is just refactoring, to make the functions accessible outside xlog.c.
A followup patch will make use of that, to allow fetching timeline history
files over streaming replication.
When the startup process restores a WAL file from the archive, it deletes
any old file with the same name and renames the new file in its place. On
Windows, however, when a file is deleted, it still lingers as long as a
process holds a file handle open on it. With cascading replication, a
walsender process can hold the old file open, so the rename() in the startup
process would fail. To fix that, rename the old file to a temporary name, to
make the original file name available for reuse, before deleting the old
file.
Give the correct name of the GUC parameter being complained of.
Also, emit a more suitable SQLSTATE (INVALID_PARAMETER_VALUE,
not the default INTERNAL_ERROR).
Gurjeet Singh, errcode adjustment by me
The cascading replication code assumed that the current RecoveryTargetTLI
never changes, but that's not true with recovery_target_timeline='latest'.
The obvious upshot of that is that RecoveryTargetTLI in shared memory needs
to be protected by a lock. A less obvious consequence is that when a
cascading standby is connected, and the standby switches to a new target
timeline after scanning the archive, it will continue to stream WAL to the
cascading standby, but from a wrong file, ie. the file of the previous
timeline. For example, if the standby is currently streaming from the middle
of file 000000010000000000000005, and the timeline changes, the standby
will continue to stream from that file. However, the WAL on the new
timeline is in file 000000020000000000000005, so the standby sends garbage
from 000000010000000000000005 to the cascading standby, instead of the
correct WAL from file 000000020000000000000005.
This also fixes a related bug where a partial WAL segment is restored from
the archive and streamed to a cascading standby. The code assumed that when
a WAL segment is copied from the archive, it can immediately be fully
streamed to a cascading standby. However, if the segment is only partially
filled, ie. has the right size, but only N first bytes contain valid WAL,
that's not safe. That can happen if a partial WAL segment is manually copied
to the archive, or if a partial WAL segment is archived because a server is
started up on a new timeline within that segment. The cascading standby will
get confused if the WAL it received is not valid, and will get stuck until
it's restarted. This patch fixes that problem by not allowing WAL restored
from the archive to be streamed to a cascading standby until it's been
replayed, and thus validated.
This gets rid of a dangerous-looking use of the not-volatile XLogCtl
pointer in a couple of spinlock-protected sections, where the normal
coding rule is that you should only access shared memory through a
pointer-to-volatile. I think the risk is only hypothetical not actual,
since for there to be a bug the compiler would have to move the spinlock
acquire or release across the memcpy() call, which one sincerely hopes
it will not. Still, it looks cleaner this way.
Per comment from Daniel Farina and subsequent discussion.
This reduces unnecessary exposure of other headers through htup.h, which
is very widely included by many files.
I have chosen to move the function prototypes to the new file as well,
because that means htup.h no longer needs to include tupdesc.h. In
itself this doesn't have much effect in indirect inclusion of tupdesc.h
throughout the tree, because it's also required by execnodes.h; but it's
something to explore in the future, and it seemed best to do the htup.h
change now while I'm busy with it.
The heapam XLog functions are used by other modules, not all of which
are interested in the rest of the heapam API. With this, we let them
get just the XLog stuff in which they are interested and not pollute
them with unrelated includes.
Also, since heapam.h no longer requires xlog.h, many files that do
include heapam.h no longer get xlog.h automatically, including a few
headers. This is useful because heapam.h is getting pulled in by
execnodes.h, which is in turn included by a lot of files.
This improves on commit 51fed14d73 by
eliminating the assumption that we can form <some pointer value> +
<some offset> without overflow. The entire point of those tests is that
we don't trust the offset value, so coding them in a way that could wrap
around if the buffer happens to be near the top of memory doesn't seem
sound. Instead, track the remaining space as a size_t variable and
compare offsets against that.
Also, improve comment about why we need the extra early check on
xl_tot_len.
If a WAL record header was split across pages, but xl_tot_len was 0, we
would get confused and conclude that we had already read the whole record,
and proceed to CRC check it. That can lead to a crash in RecordIsValid(),
which isn't careful to not read beyond end-of-record, as defined by
xl_tot_len.
Add an explicit sanity check for xl_tot_len <= SizeOfXlogRecord. Also,
make RecordIsValid() more robust by checking in each step that it doesn't
try to access memory beyond end of record, even if a length field in the
record's or a backup block's header is bogus.
Per report and analysis by Tom Lane.
Cascading replication copied the incoming file into pg_xlog but
didn't set path correctly, so the first attempt to open file failed
causing it to loop around and look for file in pg_xlog. So the
earlier coding worked, but accidentally rather than by design.
Spotted by Fujii Masao, fix by Fujii Masao and Simon Riggs
This was broken in commit ed0b409d22,
which revised the GlobalTransactionData struct to not include the
associated PGPROC as its first member, but overlooked one place where
a cast was used in reliance on that equivalence.
The most effective way of fixing this seems to be to create a new function
that looks up the GlobalTransactionData struct given the XID, and make
both TwoPhaseGetDummyBackendId and TwoPhaseGetDummyProc rely on that.
Per report from Robert Ross.
mdinit() was misusing IsBootstrapProcessingMode() to decide whether to
create an fsync pending-operations table in the current process. This led
to creating a table not only in the startup and checkpointer processes as
intended, but also in the bgwriter process, not to mention other auxiliary
processes such as walwriter and walreceiver. Creation of the table in the
bgwriter is fatal, because it absorbs fsync requests that should have gone
to the checkpointer; instead they just sit in bgwriter local memory and are
never acted on. So writes performed by the bgwriter were not being fsync'd
which could result in data loss after an OS crash. I think there is no
live bug with respect to walwriter and walreceiver because those never
perform any writes of shared buffers; but the potential is there for
future breakage in those processes too.
To fix, make AuxiliaryProcessMain() export the current process's
AuxProcType as a global variable, and then make mdinit() test directly for
the types of aux process that should have a pendingOpsTable. Having done
that, we might as well also get rid of the random bool flags such as
am_walreceiver that some of the aux processes had grown. (Note that we
could not have fixed the bug by examining those variables in mdinit(),
because it's called from BaseInit() which is run by AuxiliaryProcessMain()
before entering any of the process-type-specific code.)
Back-patch to 9.2, where the problem was introduced by the split-up of
bgwriter and checkpointer processes. The bogus pendingOpsTable exists
in walwriter and walreceiver processes in earlier branches, but absent
any evidence that it causes actual problems there, I'll leave the older
branches alone.
Instead of letting every backend participating in a group commit wait
independently, have the first one that becomes ready to flush WAL wait
for the configured delay, and let all the others wait just long enough
for that first process to complete its flush. This greatly increases
the chances of being able to configure a commit_delay setting that
actually improves performance.
As a side consequence of this change, commit_delay now affects all WAL
flushes, rather than just commits. There was some discussion on
pgsql-hackers about whether to rename the GUC to, say, wal_flush_delay,
but in the absence of consensus I am leaving it alone for now.
Peter Geoghegan, with some changes, mostly to the documentation, by me.
Per testing by Andres Freund, this improves replication performance
and reduces replication latency and latency jitter. I was a bit
concerned about moving more work into XLogInsert, but testing seems
to show that it's not a problem in practice.
Along the way, improve comments for WaitLatchOrSocket.
Andres Freund. Review and stylistic cleanup by me.
If the record header is garbled, we're now quite likely to notice it before
we try to make a bogus memory allocation and run out of memory. That can
still happen, if the xlog record is split across pages (we cannot verify
the record header until reading the next page in that scenario), but this
reduces the chances. An out-of-memory is treated as a corrupt record
anyway, so this isn't a correctness issue, just a case of giving a better
error message.
Per Amit Kapila's suggestion.
This simplifies code that needs to do arithmetic on XLogRecPtrs.
To avoid changing on-disk format of data pages, the LSN on data pages is
still stored in the old format. That should keep pg_upgrade happy. However,
we have XLogRecPtrs embedded in the control file, and in the structs that
are sent over the replication protocol, so this changes breaks compatibility
of pg_basebackup and server. I didn't do anything about this in this patch,
per discussion on -hackers, the right thing to do would to be to change the
replication protocol to be architecture-independent, so that you could use
a newer version of pg_receivexlog, for example, against an older server
version.
This saves a few bytes of WAL space, but the real motivation is to make it
predictable how much WAL space a record requires, as it no longer depends
on whether we need to waste the last few bytes at end of WAL page because
the header doesn't fit.
The total length field of WAL record, xl_tot_len, is moved to the beginning
of the WAL record header, so that it is still always found on the first page
where a WAL record begins.
Bump WAL version number again as this is an incompatible change.
The continuation record only contained one field, xl_rem_len, so it makes
things simpler to just include it in the WAL page header. This wastes four
bytes on pages that don't begin with a continuation from previos page, plus
four bytes on every page, because of padding.
The motivation of this is to make it easier to calculate how much space a
WAL record needs. Before this patch, it depended on how many page boundaries
the record crosses. The motivation of that, in turn, is to separate the
allocation of space in the WAL from the copying of the record data to the
allocated space. Keeping the calculation of space required simple helps to
keep the critical section of allocating the space from WAL short. But that's
not included in this patch yet.
Bump WAL version number again, as this is an incompatible change.
The comments claimed that wasting the last segment made it easier to do
calculations with XLogRecPtrs, because you don't have problems representing
last-byte-position-plus-1 that way. In my experience, however, it only made
things more complicated, because the there was two ways to represent the
boundary at the beginning of a logical log file: logid = n+1 and xrecoff = 0,
or as xlogid = n and xrecoff = 4GB - XLOG_SEG_SIZE. Some functions were
picky about which representation was used.
Also, use a 64-bit segment number instead of the log/seg combination, to
point to a certain WAL segment. We assume that all platforms have a working
64-bit integer type nowadays.
This is an incompatible change in WAL format, so bumping WAL version number.
There's no need to hold onto the locks until the files are needed,
and by doing it this way, we reduce the impact on other backends who
may be awaiting locks we hold.
Noah Misch
This reverts commit 18fb9d8d21. Per
discussion, it does not seem like a good idea to allow committed changes to
go un-checkpointed indefinitely, as could happen in a low-traffic server;
that makes us entirely reliant on the WAL stream with no redundancy that
might aid data recovery in case of disk failure.
This re-introduces the original problem of hot-standby setups generating a
small continuing stream of WAL traffic even when idle, but there are other
ways to address that without compromising crash recovery, so we'll revisit
that issue in a future release cycle.
This provides a speedup of about 4X when NBuffers is large enough.
There is also a useful reduction in sinval traffic, since we
only do CacheInvalidateSmgr() once not once per fork.
Simon Riggs, reviewed and somewhat revised by Tom Lane
WALSender now woken up after each background flush by WALwriter, avoiding
multi-second replication delay for an all-async commit workload.
Replication delay reduced from 7s with default settings to 200ms and often
much less, allowing significantly reduced data loss at failover.
Andres Freund and Simon Riggs
AbortOutOfAnyTransaction failed to do anything if the state it saw on
entry corresponded to failing partway through StartTransaction. I fixed
AbortCurrentTransaction to cope with that case way back in commit
60b2444cc3, but evidently overlooked that
AbortOutOfAnyTransaction should do likewise.
Back-patch to all supported branches. It's not clear that this omission
has any more-than-cosmetic consequences, but it's also not clear that it
doesn't, so back-patching seems the least risky choice.
When the "hot" members of PGPROC were split off to separate PGXACT structs,
many PGPROC fields referred to in comments were moved to PGXACT, but the
comments were neglected in the commit. Mostly this is just a search/replace
of PGPROC with PGXACT, but the way the dummy PGPROC entries are created for
prepared transactions changed more, making some of the comments totally
bogus.
Noah Misch
Users of asynchronous-commit mode expect there to be a guaranteed maximum
delay before an async commit's WAL records get flushed to disk. The
original version of the walwriter hibernation patch broke that. Add an
extra shared-memory flag to allow async commits to kick the walwriter out
of hibernation mode, without adding any noticeable overhead in cases where
no action is needed.
This patch modifies the walwriter process so that, when it has not found
anything useful to do for many consecutive wakeup cycles, it extends its
sleep time to reduce the server's idle power consumption. It reverts to
normal as soon as it's done any successful flushes. It's still true that
during any async commit, backends check for completed, unflushed pages of
WAL and signal the walwriter if there are any; so that in practice the
walwriter can get awakened and returned to normal operation sooner than the
sleep time might suggest.
Also, improve the checkpointer so that it uses a latch and a computed delay
time to not wake up at all except when it has something to do, replacing a
previous hardcoded 0.5 sec wakeup cycle. This also is primarily useful for
reducing the server's power consumption when idle.
In passing, get rid of the dedicated latch for signaling the walwriter in
favor of using its procLatch, since that comports better with possible
generic signal handlers using that latch. Also, fix a pre-existing bug
with failure to save/restore errno in walwriter's signal handlers.
Peter Geoghegan, somewhat simplified by Tom
This patch adjusts the core statistics views to match the decision already
taken for pg_stat_statements, that values representing elapsed time should
be represented as float8 and measured in milliseconds. By using float8,
we are no longer tied to a specific maximum precision of timing data.
(Internally, it's still microseconds, but we could now change that without
needing changes at the SQL level.)
The columns affected are
pg_stat_bgwriter.checkpoint_write_time
pg_stat_bgwriter.checkpoint_sync_time
pg_stat_database.blk_read_time
pg_stat_database.blk_write_time
pg_stat_user_functions.total_time
pg_stat_user_functions.self_time
pg_stat_xact_user_functions.total_time
pg_stat_xact_user_functions.self_time
The first four of these are new in 9.2, so there is no compatibility issue
from changing them. The others require a release note comment that they
are now double precision (and can show a fractional part) rather than
bigint as before; also their underlying statistics functions now match
the column definitions, instead of returning bigint microseconds.
The previous code could cause a backend crash after BEGIN; SAVEPOINT a;
LOCK TABLE foo (interrupted by ^C or statement timeout); ROLLBACK TO
SAVEPOINT a; LOCK TABLE foo, and might have leaked strong-lock counts
in other situations.
Report by Zoltán Böszörményi; patch review by Jeff Davis.
When using synchronous replication, we waited for the commit record to be
replicated, but if we our transaction didn't write any other WAL records,
that's not required because we don't even flush the WAL locally to disk in
that case. This lead to long waits when committing a transaction that only
modified a temporary table. Bug spotted by Thom Brown.
Initialise ckptXidEpoch from starting checkpoint and maintain the correct
value as we roll forwards. This allows GetNextXidAndEpoch() to return the
correct epoch when executed during recovery. Backpatch to 9.0 when the
problem is first observable by a user.
Bug report from Daniel Farina
This simplifies the code a little bit. The new rule is that to update
XLogCtl->LogwrtResult, you must hold both WALWriteLock and info_lck, whereas
before we had two copies, one that was protected by WALWriteLock and another
protected by info_lck. The code that updates them was already holding both
locks, so merging the two is trivial.
The third copy, XLogCtl->Insert.LogwrtResult, was not totally redundant, it
was used in AdvanceXLInsertBuffer to update the backend-local copy, before
acquiring the info_lck to read the up-to-date value. But the value of that
seems dubious; at best it's saving one spinlock acquisition per completed
WAL page, which is not significant compared to all the other work involved.
And in practice, it's probably not saving even that much.
It's harmless to do full page writes even when not strictly necessary, so
when turning full_page_writes on, we can set the global flag first, and then
call XLogInsert. Likewise, when turning it off, we can write the WAL record
first, and then clear the flag. This way XLogInsert doesn't need any special
handling of the XLOG_FPW_CHANGE record type. XLogInsert is complicated
enough already, so anything we can keep away from there is a good thing.
Actually I don't think the atomicity of the shared memory flag matters,
anyway, because we only write the XLOG_FPW_CHANGE at the end of recovery,
when there are no concurrent WAL insertions going on. But might as well make
it safe, in case we allow changing full_page_writes on the fly in the
future.
Now that we have validate_xlog_location, call it from the previously
existing functions taking xlog locatoins as a string input.
Suggested by Fujii Masao
Comparing two xlog locations are useful for example when calculating
replication lag.
Euler Taveira de Oliveira, reviewed by Fujii Masao, and some cleanups
from me
Originally, most of this code assumed that no Postgres backends could be
running concurrently with it, and so no locking could be needed. That
assumption fails in Hot Standby. While it's still true that Hot Standby
backends should never change values like nextXid, they can examine them,
and consistency is important in some cases such as when computing a
snapshot. Therefore, prudence requires that WAL replay code obtain the
relevant locks when modifying such variables, even though it can examine
them without taking a lock. We were following that coding rule in some
places but not all. This commit applies the coding rule uniformly to all
updates of ShmemVariableCache and MultiXactState fields; a search of the
replay routines did not find any other cases that seemed to be at risk.
In addition, this commit fixes a longstanding thinko in replay of NEXTOID
and checkpoint records: we tried to advance nextOid only if it was behind
the value in the WAL record, but the comparison would draw the wrong
conclusion if OID wraparound had occurred since the previous value.
Better to just unconditionally assign the new value, since OID assignment
shouldn't be happening during replay anyway.
The additional locking seems to be more in the nature of future-proofing
than fixing any live bug, so I am not going to back-patch it. The NEXTOID
fix will be back-patched separately.
RestoreBkpBlocks was in the habit of zeroing and refilling the target
buffer; which was perfectly safe when the code was written, but is unsafe
during Hot Standby operation. The reason is that we have coding rules
that allow backends to continue accessing a tuple in a heap relation while
holding only a pin on its buffer. Such a backend could see transiently
zeroed data, if WAL replay had occasion to change other data on the page.
This has been shown to be the cause of bug #6425 from Duncan Rance (who
deserves kudos for developing a sufficiently-reproducible test case) as
well as Bridget Frey's re-report of bug #6200. It most likely explains the
original report as well, though we don't yet have confirmation of that.
To fix, change the code so that only bytes that are supposed to change will
change, even transiently. This actually saves cycles in RestoreBkpBlocks,
since it's not writing the same bytes twice.
Also fix seq_redo, which has the same disease, though it has to work a bit
harder to meet the requirement.
So far as I can tell, no other WAL replay routines have this type of bug.
In particular, the index-related replay routines, which would certainly be
broken if they had to meet the same standard, are not at risk because we
do not have coding rules that allow access to an index page when not
holding a buffer lock on it.
Back-patch to 9.0 where Hot Standby was added.
When a backend needs to flush the WAL, and someone else is already flushing
the WAL, wait until it releases the WALInsertLock and check if we still need
to do the flush or if the other backend already did the work for us, before
acquiring WALInsertLock. This helps group commit, because when the WAL flush
finishes, all the backends that were waiting for it can be woken up in one
go, and the can all concurrently observe that they're done, rather than
waking them up one by one in a cascading fashion.
This is based on a new LWLock function, LWLockWaitUntilFree(), which has
peculiar semantics. If the lock is immediately free, it grabs the lock and
returns true. If it's not free, it waits until it is released, but then
returns false without grabbing the lock. This is used in XLogFlush(), so
that when the lock is acquired, the backend flushes the WAL, but if it's
not, the backend first checks the current flush location before retrying.
Original patch and benchmarking by Peter Geoghegan and Simon Riggs, although
this patch as committed ended up being very different from that.
Base backup follows recommended procedure, plus goes to great
lengths to ensure that partial page writes are avoided.
Jun Ishizuka and Fujii Masao, with minor modifications
Previously we used ReadRecPtr rather than EndRecPtr, which was
not a serious error but caused pg_stat_replication to report
incorrect replay_location until at least one WAL record is replayed.
Fujii Masao
constructed before acquiring WALInsertLock, which slightly reduces the time
the lock is held. Although I could not measure any benefit in benchmarks,
the code is more readable this way.
Previously, this was hardcoded: we always had 8. Performance testing
shows that isn't enough, especially on big SMP systems, so we allow it
to scale up as high as 32 when there's adequate memory. On the flip
side, when shared_buffers is very small, drop the number of CLOG buffers
down to as little as 4, so that we can start the postmaster even
when very little shared memory is available.
Per extensive discussion with Simon Riggs, Tom Lane, and others on
pgsql-hackers.
smgrdounlink takes care to not throw an ERROR if it fails to unlink
something, but that caution was rendered useless by commit
3396000684, which put an smgrexists call in
front of it; smgrexists *does* throw error if anything looks funny, such
as getting a permissions error from trying to open the file. If that
happens post-commit, you get a PANIC, and what's worse the same logic
appears in the WAL replay code, so the database even fails to restart.
Restore the intended behavior by removing the smgrexists call --- it isn't
accomplishing anything that we can't do better by adjusting mdunlink's
ideas of whether it ought to warn about ENOENT or not.
Per report from Joseph Shraibman of unrecoverable crash after trying to
drop a table whose FSM fork had somehow gotten chmod'd to 000 permissions.
Backpatch to 8.4, where the bogus coding was introduced.
SP-GiST is comparable to GiST in flexibility, but supports non-balanced
partitioned search structures rather than balanced trees. As described at
PGCon 2011, this new indexing structure can beat GiST in both index build
time and query speed for search problems that it is well matched to.
There are a number of areas that could still use improvement, but at this
point the code seems committable.
Teodor Sigaev and Oleg Bartunov, with considerable revisions by Tom Lane
Removing this bit from xl_info allows us to restore the old limit of four
(not three) separate pages touched by a WAL record, which is needed for the
upcoming SP-GiST feature, and will likely be useful elsewhere in future.
When we implemented XLR_BKP_REMOVABLE in 2007, we had to do it like that
because no special WAL-visible action was taken when starting a backup.
However, now we force a segment switch when starting a backup, so a
compressing WAL archiver (such as pglesslog) that uses the state shown in
the current page header will not be fooled as to removability of backup
blocks. The only downside is that the archiver will not return to
compressing mode for up to one WAL page after the backup is over, which is
a small price to pay for getting back the extra xl_info bit. In any case
the archiver could look for XLOG_BACKUP_END records if it thought it was
worth the trouble to do so.
Bump XLOG_PAGE_MAGIC since this is effectively a change in WAL format.
we don't reach consistency before replaying all of the WAL. Rename the
variable to reachedConsistency, to make its intention clearer.
In master, that was an active bug because of the recent patch to
immediately PANIC if a reference to a missing page is found in WAL after
reaching consistency, as Tom Lane's test case demonstrated. In 9.1 and 9.0,
the only consequence was a misleading "consistent recovery state reached at
%X/%X" message in the log at the beginning of crash recovery (the database
is not consistent at that point yet). In 8.4, the log message was not
printed in crash recovery, even though there was a similar
reachedMinRecoveryPoint local variable that was also set early. So,
backpatch to 9.1 and 9.0.
invalid-page hash table, PANIC immediately. Immediate PANIC is much better
than waiting for end-of-recovery, which is what we did before, because the
end-of-recovery might not come until months later if this is a standby
server.
Also refrain from creating a restartpoint if there are invalid-page entries
in the hash table. Restarting recovery from such a restartpoint would not
see the invalid references, and wouldn't be able to cross-check them when
consistency is reached. That wouldn't matter when things are going smoothly,
but the more sanity checks you have the better.
Fujii Masao
This speeds up snapshot-taking and reduces ProcArrayLock contention.
Also, the PGPROC (and PGXACT) structures used by two-phase commit are
now allocated as part of the main array, rather than in a separate
array, and we keep ProcArray sorted in pointer order. These changes
are intended to minimize the number of cache lines that must be pulled
in to take a snapshot, and testing shows a substantial increase in
performance on both read and write workloads at high concurrencies.
Pavan Deolasee, Heikki Linnakangas, Robert Haas
Previously we waited for wal_writer_delay before flushing WAL. Now
we also wake WALWriter as soon as a WAL buffer page has filled.
Significant effect observed on performance of asynchronous commits
by Robert Haas, attributed to the ability to set hint bits on tuples
earlier and so reducing contention caused by clog lookups.
Previously, we skipped a checkpoint if no WAL had been written since
last checkpoint, though this does not appear in user documentation.
As of now, we skip a checkpoint until we have written at least one
enough WAL to switch the next WAL file. This greatly reduces the
level of activity and number of WAL messages generated by a very
low activity server. This is safe because the purpose of a checkpoint
is to act as a starting place for a recovery, in case of crash.
This patch maintains minimal WAL volume for replay in case of crash,
thus maintaining very low crash recovery time.
There was a timing window between when oldestActiveXid was derived
and when it should have been derived that only shows itself under
heavy load. Move code around to ensure correct timing of derivation.
No change to StartupSUBTRANS() code, which is where this failed.
Bug report by Chris Redekop
A transaction can export a snapshot with pg_export_snapshot(), and then
others can import it with SET TRANSACTION SNAPSHOT. The data does not
leave the server so there are not security issues. A snapshot can only
be imported while the exporting transaction is still running, and there
are some other restrictions.
I'm not totally convinced that we've covered all the bases for SSI (true
serializable) mode, but it works fine for lesser isolation modes.
Joachim Wieland, reviewed by Marko Tiikkaja, and rather heavily modified
by Tom Lane
This is merely an exercise in satisfying pedants, not a bug fix, because
in every case we were checking for failure later with ferror(), or else
there was nothing useful to be done about a failure anyway. Document
the latter cases.
Previously, the code assumed that the only possible action to take was
to delete files behind a certain cutoff point. The async notify code
was already a crock: it used a different "pagePrecedes" function for
truncation than for regular operation. By allowing it to pass a
callback to SlruScanDirectory it can do cleanly exactly what it needs to
do.
The clog.c code also had its own use for SlruScanDirectory, which is
made a bit simpler with this.
This patch has two distinct purposes: to report multiple problems in
postgresql.conf rather than always bailing out after the first one,
and to change the policy for whether changes are applied when there are
unrelated errors in postgresql.conf.
Formerly the policy was to apply no changes if any errors could be
detected, but that had a significant consistency problem, because in some
cases specific values might be seen as valid by some processes but invalid
by others. This meant that the latter processes would fail to adopt
changes in other parameters even though the former processes had done so.
The new policy is that during SIGHUP, the file is rejected as a whole
if there are any errors in the "name = value" syntax, or if any lines
attempt to set nonexistent built-in parameters, or if any lines attempt
to set custom parameters whose prefix is not listed in (the new value of)
custom_variable_classes. These tests should always give the same results
in all processes, and provide what seems a reasonably robust defense
against loading values from badly corrupted config files. If these tests
pass, all processes will apply all settings that they individually see as
good, ignoring (but logging) any they don't.
In addition, the postmaster does not abandon reading a configuration file
after the first syntax error, but continues to read the file and report
syntax errors (up to a maximum of 100 syntax errors per file).
The postmaster will still refuse to start up if the configuration file
contains any errors at startup time, but these changes allow multiple
errors to be detected and reported before quitting.
Alexey Klyukin, reviewed by Andy Colson and av (Alexander ?)
with some additional hacking by Tom Lane
In REPEATABLE READ (nee SERIALIZABLE) mode, an attempt to do
GetTransactionSnapshot() between AbortTransaction and CleanupTransaction
failed, because GetTransactionSnapshot would recompute the transaction
snapshot (which is already wrong, given the isolation mode) and then
re-register it in the TopTransactionResourceOwner, leading to an Assert
because the TopTransactionResourceOwner should be empty of resources after
AbortTransaction. This is the root cause of bug #6218 from Yamamoto
Takashi. While changing plancache.c to avoid requesting a snapshot when
handling a ROLLBACK masks the problem, I think this is really a snapmgr.c
bug: it's lower-level than the resource manager mechanism and should not be
shutting itself down before we unwind resource manager resources. However,
just postponing the release of the transaction snapshot until cleanup time
didn't work because of the circular dependency with
TopTransactionResourceOwner. Fix by managing the internal reference to
that snapshot manually instead of depending on TopTransactionResourceOwner.
This saves a few cycles as well as making the module layering more
straightforward. predicate.c's dependencies on TopTransactionResourceOwner
go away too.
I think this is a longstanding bug, but there's no evidence that it's more
than a latent bug, so it doesn't seem worth any risk of back-patching.
As per my recent proposal, this refactors things so that these typedefs and
macros are available in a header that can be included in frontend-ish code.
I also changed various headers that were undesirably including
utils/timestamp.h to include datatype/timestamp.h instead. Unsurprisingly,
this showed that half the system was getting utils/timestamp.h by way of
xlog.h.
No actual code changes here, just header refactoring.
walsender.h should depend on xlog.h, not vice versa. (Actually, the
inclusion was circular until a couple hours ago, which was even sillier;
but Bruce broke it in the expedient rather than logically correct
direction.) Because of that poor decision, plus blind application of
pgrminclude, we had a situation where half the system was depending on
xlog.h to include such unrelated stuff as array.h and guc.h. Clean up
the header inclusion, and manually revert a lot of what pgrminclude had
done so things build again.
This episode reinforces my feeling that pgrminclude should not be run
without adult supervision. Inclusion changes in header files in particular
need to be reviewed with great care. More generally, it'd be good if we
had a clearer notion of module layering to dictate which headers can sanely
include which others ... but that's a big task for another day.
The previous code tried to synchronize by unlinking the init file twice,
but that doesn't actually work: it leaves a window wherein a third process
could read the already-stale init file but miss the SI messages that would
tell it the data is stale. The result would be bizarre failures in catalog
accesses, typically "could not read block 0 in file ..." later during
startup.
Instead, hold RelCacheInitLock across both the unlink and the sending of
the SI messages. This is more straightforward, and might even be a bit
faster since only one unlink call is needed.
This has been wrong since it was put in (in 2002!), so back-patch to all
supported releases.
In pursuit of this (and with the expectation that WaitLatch will be needed
in more places), convert the latch field that was already added to PGPROC
for sync rep into a generic latch that is activated for all PGPROC-owning
processes, and change many of the standard backend signal handlers to set
that latch when a signal happens. This will allow WaitLatch callers to be
wakened properly by these signals.
In passing, fix a whole bunch of signal handlers that had been hacked to do
things that might change errno, without adding the necessary save/restore
logic for errno. Also make some minor fixes in unix_latch.c, and clean
up bizarre and unsafe scheme for disowning the process's latch. Much of
this has to be back-patched into 9.1.
Peter Geoghegan, with additional work by Tom
streamed backup, throw an error and refuse to start up. The restore has not
finished correctly in that case and the data directory is possibly corrupt.
We already errored out in case of archive recovery, but could not during
crash recovery because we couldn't distinguish between the case that
pg_start_backup() was called and the database then crashed (must not error,
data is OK), and the case that we're restoring from a backup and not all
the needed WAL was replayed (data can be corrupt).
To distinguish those cases, add a line to backup_label to indicate
whether the backup was taken with pg_start/stop_backup(), or by streaming
(ie. pg_basebackup).
This requires re-initdb, because of a new field added to the control file.
The original definition had the problem that timeouts exceeding about 2100
seconds couldn't be specified on 32-bit machines. Milliseconds seem like
sufficient resolution, and finer grain than that would be fantasy anyway
on many platforms.
Back-patch to 9.1 so that this aspect of the latch API won't change between
9.1 and later releases.
Peter Geoghegan
Subtransaction locks now released en masse at main commit, rather than
repeatedly re-scanning for locks as we ascend the nested transaction tree.
Split transaction state TBLOCK_SUBEND into two states, TBLOCK_SUBCOMMIT
and TBLOCK_SUBRELEASE to allow the commit path to be optimised using
the existing code in ResourceOwnerRelease() which appears to have been
intended for this usage, judging from comments therein.
Standby servers can now have WALSender processes, which can work with
either WALReceiver or archive_commands to pass data. Fully updated
docs, including new conceptual terms of sending server, upstream and
downstream servers. WALSenders terminated when promote to master.
Fujii Masao, review, rework and doc rewrite by Simon Riggs
detect postmaster death. Postmaster keeps the write-end of the pipe open,
so when it dies, children get EOF in the read-end. That can conveniently
be waited for in select(), which allows eliminating some of the polling
loops that check for postmaster death. This patch doesn't yet change all
the loops to use the new mechanism, expect a follow-on patch to do that.
This changes the interface to WaitLatch, so that it takes as argument a
bitmask of events that it waits for. Possible events are latch set, timeout,
postmaster death, and socket becoming readable or writeable.
The pipe method behaves slightly differently from the kill() method
previously used in PostmasterIsAlive() in the case that postmaster has died,
but its parent has not yet read its exit code with waitpid(). The pipe
returns EOF as soon as the process dies, but kill() continues to return
true until waitpid() has been called (IOW while the process is a zombie).
Because of that, change PostmasterIsAlive() to use the pipe too, otherwise
WaitLatch() would return immediately with WL_POSTMASTER_DEATH, while
PostmasterIsAlive() would claim it's still alive. That could easily lead to
busy-waiting while postmaster is in zombie state.
Peter Geoghegan with further changes by me, reviewed by Fujii Masao and
Florian Pflug.
XLOG_XACT_COMMIT_COMPACT leaves out invalidation messages and relfilenodes,
saving considerable space for the vast majority of transaction commits.
XLOG_XACT_COMMIT keeps same definition as XLOG_PAGE_MAGIC 0xD067 and earlier.
Leonardo Francalanci and Simon Riggs
This involves two main changes from the previous behavior. First,
when we set a bit in the visibility map, emit a new WAL record of type
XLOG_HEAP2_VISIBLE. Replay sets the page-level PD_ALL_VISIBLE bit and
the visibility map bit. Second, when inserting, updating, or deleting
a tuple, we can no longer get away with clearing the visibility map
bit after releasing the lock on the corresponding heap page, because
an intervening crash might leave the visibility map bit set and the
page-level bit clear. Making this work requires a bit of interface
refactoring.
In passing, a few minor but related cleanups: change the test in
visibilitymap_set and visibilitymap_clear to throw an error if the
wrong page (or no page) is pinned, rather than silently doing nothing;
this case should never occur. Also, remove duplicate definitions of
InvalidXLogRecPtr.
Patch by me, review by Noah Misch.
ReadRecord's habit of using both direct references to tmpRecPtr and
references to *RecPtr (which is pointing at tmpRecPtr) triggers an
optimization bug in gcc 4.6.0, which apparently has forgotten about
aliasing rules. Avoid the compiler bug, and make the code more readable
to boot, by getting rid of the direct references. Improve the comments
while at it.
Back-patch to all supported versions, in case they get built with 4.6.0.
Tom Lane, with some cosmetic suggestions from Alex Hunsaker
The SSI patch inserted a call of RegisterPredicateLockingXid into
GetNewTransactionId, which was a bad idea on a couple of grounds. First,
it's not necessary to hold XidGenLock while manipulating that shared
memory, and doing so is bad because XidGenLock is a high-contention lock
that should be held for as short a time as possible. (Not to mention that
it adds an entirely unnecessary deadlock hazard, since we must take
SerializableXactHashLock as well.) Second, the specific place where it was
put was between extending CLOG and advancing nextXid, which could result in
unpleasant behavior in case of a failure there. Pull the call out to
AssignTransactionId, which is much safer and arguably better from a
modularity standpoint too.
There is more work to do to clean up the failure-before-advancing-nextXid
issue, but that is a separate change that will need to be back-patched.
So for the moment I just want to make GetNewTransactionId look the same as
it did in prior versions.
Before commit c016ce7281, this wasn't
needed, but now that multiple resource manager IDs can percolate down
through here, we have to make sure we know which one we've got.
Otherwise, we can confuse (for example) an XLOG_XACT_COMMIT record
with an XLOG_CHECKPOINT_SHUTDOWN record.
Review by Jaime Casanova
crash recovery, and throw an error if not. hubert depesz lubaczewski pointed
out that that situation also happens in the crash recovery following a
system crash that happens during an online backup.
We might want to do something smarter in 9.1, like put the check back for
backups taken with pg_basebackup, but that's for another patch.
The previous functions of assign hooks are now split between check hooks
and assign hooks, where the former can fail but the latter shouldn't.
Aside from being conceptually clearer, this approach exposes the
"canonicalized" form of the variable value to guc.c without having to do
an actual assignment. And that lets us fix the problem recently noted by
Bernd Helmle that the auto-tune patch for wal_buffers resulted in bogus
log messages about "parameter "wal_buffers" cannot be changed without
restarting the server". There may be some speed advantage too, because
this design lets hook functions avoid re-parsing variable values when
restoring a previous state after a rollback (they can store a pre-parsed
representation of the value instead). This patch also resolves a
longstanding annoyance about custom error messages from variable assign
hooks: they should modify, not appear separately from, guc.c's own message
about "invalid parameter value".
Also avoid hardcoding the current default state by giving it the name
"on" and replace with a meaningful name that reflects its behaviour.
Coding only, no change in behaviour.
This means one less thing to configure when setting up synchronous
replication, and also avoids some ambiguity around what the behavior
should be when the settings of these variables conflict.
Fujii Masao, with additional hacking by me.
archive recovery.
It's possible to restore an online backup without recovery.conf, by simply
copying all the necessary WAL files to pg_xlog. "pg_basebackup -x" does that
too. That's the use case where this cross-check is useful.
Backpatch to 9.0. We used to do this in earlier versins, but in 9.0 the code
was inadvertently changed so that the check is only performed after archive
recovery.
Fujii Masao.
Change location LOG message so it works each time we pause, not
just for final pause.
Ensure that we pause only if we are in Hot Standby and can connect
to allow us to run resume function. This change supercedes the
code to override parameter recoveryPauseAtTarget to false if not
attempting to enter Hot Standby, which is now removed.
Startup process waited for cleanup lock but when hot_standby = off
the pid was not registered, so that the bgwriter would not wake
the waiting process as intended.
ensure that they use different checkpoints as the starting point. We use
the checkpoint redo location as a unique identifier for the base backup in
the end-of-backup record, and in the backup history file name.
Bug spotted by Fujii Masao.
than doing it aggressively whenever the tail-XID pointer is advanced, because
this way we don't need to do it while holding SerializableXactHashLock.
This also fixes bug #5915 spotted by YAMAMOTO Takashi, and removes an
obsolete comment spotted by Kevin Grittner.
periodically rescan the archive for new timelines, while waiting for new WAL
segments to arrive. This allows you to set up a standby server that follows
the TLI change if another standby server is promoted to master. Before this,
you had to restart the standby server to make it notice the new timeline.
This patch only scans the archive for TLI changes, it won't follow a TLI
change in streaming replication. That is much needed too, but it would be a
much bigger patch than I dare to sneak in this late in the release cycle.
There was discussion on improving the sanity checking of the WAL segments so
that the system would notice more reliably if the new timeline isn't an
ancestor of the current one, but that is not included in this patch.
Reviewed by Fujii Masao.
If a standby is broadcasting reply messages and we have named
one or more standbys in synchronous_standby_names then allow
users who set synchronous_replication to wait for commit, which
then provides strict data integrity guarantees. Design avoids
sending and receiving transaction state information so minimises
bookkeeping overheads. We synchronize with the highest priority
standby that is connected and ready to synchronize. Other standbys
can be defined to takeover in case of standby failure.
This version has very strict behaviour; more relaxed options
may be added at a later date.
Simon Riggs and Fujii Masao, with reviews by Yeb Havinga, Jaime
Casanova, Heikki Linnakangas and Robert Haas, plus the assistance
of many other design reviewers.
The originally committed patch for modifying CTEs didn't interact well
with EXPLAIN, as noted by myself, and also had corner-case problems with
triggers, as noted by Dean Rasheed. Those problems show it is really not
practical for ExecutorEnd to call any user-defined code; so split the
cleanup duties out into a new function ExecutorFinish, which must be called
between the last ExecutorRun call and ExecutorEnd. Some Asserts have been
added to these functions to help verify correct usage.
It is no longer necessary for callers of the executor to call
AfterTriggerBeginQuery/AfterTriggerEndQuery for themselves, as this is now
done by ExecutorStart/ExecutorFinish respectively. If you really need to
suppress that and do it for yourself, pass EXEC_FLAG_SKIP_TRIGGERS to
ExecutorStart.
Also, refactor portal commit processing to allow for the possibility that
PortalDrop will invoke user-defined code. I think this is not actually
necessary just yet, since the portal-execution-strategy logic forces any
non-pure-SELECT query to be run to completion before we will consider
committing. But it seems like good future-proofing.
Emit a log message when creating a named restore point, and improve
documentation for pg_create_restore_point().
Euler Taveira de Oliveira, per suggestions from Thom Brown, with some
additional wordsmithing by me.
Standby optionally sends back information about oldestXmin of queries
which is then checked and applied to the WALSender's proc->xmin.
GetOldestXmin() is modified slightly to agree with GetSnapshotData(),
so that all backends on primary include WALSender within their snapshots.
Note this does nothing to change the snapshot xmin on either master or
standby. Feedback piggybacks on the standby reply message.
vacuum_defer_cleanup_age is no longer used on standby, though parameter
still exists on primary, since some use cases still exist.
Simon Riggs, review comments from Fujii Masao, Heikki Linnakangas, Robert Haas
though must not update the last transaction timestamp.
Plus comment and message cleanup for recent named restore point.
Fujii Masao, minor changes by me
the standby has written, flushed, and applied the WAL. At the moment, this
is for informational purposes only, the values are only shown in
pg_stat_replication system view, but in the future they will also be needed
for synchronous replication.
Extracted from Simon riggs' synchronous replication patch by Robert Haas, with
some tweaking by me.
Specifying this option makes the server not wait for the
xlog to be archived, or emit a warning that it can't,
instead leaving the responsibility with the client.
This is useful when the log is being streamed using
the streaming protocol in parallel with the backup,
without having log archiving enabled.
new recovery.conf parameter recovery_target_name allows PITR to
specify named points as recovery targets.
Jaime Casanova, reviewed by Euler Taveira de Oliveira, plus minor edits
If the standby was streaming when trigger file arrives, check also in the
archive for additional WAL files. This is a corner case since it is
unlikely that we would trigger a failover while the master is still
available and sending data to standby, while at the same time running in
archive mode and also while the streaming standby has fallen behind archive.
Someone would eventually be unlucky; we must plug all gaps however small.
Fujii Masao
Until now, our Serializable mode has in fact been what's called Snapshot
Isolation, which allows some anomalies that could not occur in any
serialized ordering of the transactions. This patch fixes that using a
method called Serializable Snapshot Isolation, based on research papers by
Michael J. Cahill (see README-SSI for full references). In Serializable
Snapshot Isolation, transactions run like they do in Snapshot Isolation,
but a predicate lock manager observes the reads and writes performed and
aborts transactions if it detects that an anomaly might occur. This method
produces some false positives, ie. it sometimes aborts transactions even
though there is no anomaly.
To track reads we implement predicate locking, see storage/lmgr/predicate.c.
Whenever a tuple is read, a predicate lock is acquired on the tuple. Shared
memory is finite, so when a transaction takes many tuple-level locks on a
page, the locks are promoted to a single page-level lock, and further to a
single relation level lock if necessary. To lock key values with no matching
tuple, a sequential scan always takes a relation-level lock, and an index
scan acquires a page-level lock that covers the search key, whether or not
there are any matching keys at the moment.
A predicate lock doesn't conflict with any regular locks or with another
predicate locks in the normal sense. They're only used by the predicate lock
manager to detect the danger of anomalies. Only serializable transactions
participate in predicate locking, so there should be no extra overhead for
for other transactions.
Predicate locks can't be released at commit, but must be remembered until
all the transactions that overlapped with it have completed. That means that
we need to remember an unbounded amount of predicate locks, so we apply a
lossy but conservative method of tracking locks for committed transactions.
If we run short of shared memory, we overflow to a new "pg_serial" SLRU
pool.
We don't currently allow Serializable transactions in Hot Standby mode.
That would be hard, because even read-only transactions can cause anomalies
that wouldn't otherwise occur.
Serializable isolation mode now means the new fully serializable level.
Repeatable Read gives you the old Snapshot Isolation level that we have
always had.
Kevin Grittner and Dan Ports, reviewed by Jeff Davis, Heikki Linnakangas and
Anssi Kääriäinen
Prior to 9.0, restartpoints never created, deleted, or recycled WAL
files, but now they can. This code makes log_checkpoints treat
checkpoints and restartpoints symmetrically. It also adjusts up
the documentation of the parameter to mention restartpoints.
Fujii Masao. Docs by me, as suggested by Itagaki Takahiro.
With this patch, pg_basebackup doesn't write a backup_label file in the
data directory, so it doesn't interfere with a pg_start/stop_backup() based
backup anymore. backup_label is still included in the backup, but it is
injected directly into the tar stream.
Heikki Linnakangas, reviewed by Fujii Masao and Magnus Hagander.
If wal_buffers is initially set to -1 (which is now the default), it's
replaced by 1/32nd of shared_buffers, with a minimum of 8 (the old default)
and a maximum of the XLOG segment size. The allowed range for manual
settings is still from 4 up to whatever will fit in shared memory.
Greg Smith, with implementation correction by me.
Move the actual functionality into a separate function that's
easier to call internally, and change the SQL-callable function
to be a wrapper calling this.
Also create a pg_abort_backup() function, only callable internally,
that does only the most vital parts of pg_stop_backup(), making it
safe(r) to call from error handlers.
Instead, declare a public wrapper of the sole function using it for
external callers, so that they don't have to always pass a NULL
argument.
Author: Kevin Grittner
The contents of an unlogged table are WAL-logged; thus, they are not
available on standby servers and are truncated whenever the database
system enters recovery. Indexes on unlogged tables are also unlogged.
Unlogged GiST indexes are not currently supported.
This privilege is required to do Streaming Replication, instead of
superuser, making it possible to set up a SR slave that doesn't
have write permissions on the master.
Superuser privileges do NOT override this check, so in order to
use the default superuser account for replication it must be
explicitly granted the REPLICATION permissions. This is backwards
incompatible change, in the interest of higher default security.
cleanup stage to finish incomplete inserts or splits anymore. There was two
reasons for the cleanup step:
1. When a new tuple was inserted to a leaf page, the downlink in the parent
needed to be updated to contain (ie. to be consistent with) the new key.
Updating the parent in turn might require recursively updating the parent of
the parent. We now handle that by updating the parent while traversing down
the tree, so that when we insert the leaf tuple, all the parents are already
consistent with the new key, and the tree is consistent at every step.
2. When a page is split, we need to insert the downlink for the new right
page(s), and update the downlink for the original page to not include keys
that moved to the right page(s). We now handle that by setting a new flag,
F_FOLLOW_RIGHT, on the non-rightmost pages in the split. When that flag is
set, scans always follow the rightlink, regardless of the NSN mechanism used
to detect concurrent page splits. That way the tree is consistent right after
split, even though the downlink is still missing. This is very similar to the
way B-tree splits are handled. When the downlink is inserted in the parent,
the flag is cleared. To keep the insertion algorithm simple, when an
insertion sees an incomplete split, indicated by the F_FOLLOW_RIGHT flag, it
finishes the split before doing anything else.
These changes allow removing the whole "invalid tuple" mechanism, but I
retained the scan code to still follow invalid tuples correctly. While we
don't create any such tuples anymore, we want to handle them gracefully in
case you pg_upgrade a GiST index that has them. If we encounter any on an
insert, though, we just throw an error saying that you need to REINDEX.
The issue that got me into doing this is that if you did a checkpoint while
an insert or split was in progress, and the checkpoint finishes quickly so
that there is no WAL record related to the insert between RedoRecPtr and the
checkpoint record, recovery from that checkpoint would not know to finish
the incomplete insert. IOW, we have the same issue we solved with the
rm_safe_restartpoint mechanism during normal operation too. It's highly
unlikely to happen in practice, and this fix is far too large to backpatch,
so we're just going to live with in previous versions, but this refactoring
fixes it going forward.
With this patch, you don't get the annoying
'index "FOO" needs VACUUM or REINDEX to finish crash recovery' notices
anymore if you crash at an unfortunate moment.
This case can arise if a transaction has written data, but only to
temporary tables. Loss of the commit record in case of a crash won't
matter, because the temporary tables will be lost anyway.
Reviewed by Heikki Linnakangas and Simon Riggs.
Purely cosmetic patch to make our coding standards more consistent ---
we were doing symbolic some places and octal other places. This patch
fixes all C-coded uses of mkdir, chmod, and umask. There might be some
other calls I missed. Inconsistency noted while researching tablespace
directory permissions issue.
First, avoid scanning the whole ProcArray once we know there
are at least commit_siblings active; second, skip the check
altogether if commit_siblings = 0.
Greg Smith
an old transaction running in the master, and a lot of transactions have
started and finished since, and a WAL-record is written in the gap between
the creating the running-xacts snapshot and WAL-logging it, recovery will fail
with "too many KnownAssignedXids" error. This bug was reported by
Joachim Wieland on Nov 19th.
In the same scenario, when fewer transactions have started so that all the
xids fit in KnownAssignedXids despite the first bug, a more serious bug
arises. We incorrectly initialize the clog code with the oldest still running
transaction, and when we see the WAL record belonging to a transaction with
an XID larger than one that committed already before the checkpoint we're
recovering from, we zero the clog page containing the already committed
transaction, leading to data loss.
In hindsight, trying to track xids in the known-assigned-xids array before
seeing the running-xacts record was too complicated. To fix that, hold
XidGenLock while the running-xacts snapshot is taken and WAL-logged. That
ensures that no transaction can begin or end in that gap, so that in recvoery
we know that the snapshot contains all transactions running at that point in
WAL.
This eliminates some crufty, special-purpose code and, as a non-trivial
side benefit, allows recovery.conf parameters to be unquoted.
Dimitri Fontaine, with review and cleanup by Alvaro Herrera, Itagaki
Takahiro, and me.
location read from backup label file can be found: wasShutdown was set
incorrectly when a backup label file was found.
Jeff Davis, with a little tweaking by me.
rather than 0/0, so that we can safely use 0/0 as an invalid value. This is a
more future-proof fix for the corner-case bug in streaming replication that
was fixed yesterday. We had a similar corner-case bug with log/seg 0/0 back in
February as well. Avoiding 0/0 as a valid value should prevent bugs like that
in the future. Per Tom Lane's idea.
Back-patch to 9.0. Since this only affects bootstrapping, it makes no
difference to existing installations. We don't need to worry about the
bug in existing installations, because if you've managed to get past the
initial base backup already, you won't hit the bug in the future either.
streaming replication. We used log/seg 0/0 to indicate that no WAL segments
have been removed since startup, but 0/0 is a valid value for the very first
WAL segment after initdb. To make that disambiguous, store
(latest removed WAL segment + 1) in the global variable.
Per report from Matt Chesler, also reproduced by Greg Smith.
that WAL file containing the checkpoint redo-location can be found. This
avoids making the cluster irrecoverable if the redo location is in an earlie
WAL file than the checkpoint record.
Report, analysis and patch by Jeff Davis, with small changes by me.
outside a transaction.
This repairs brain fade in my patch of 2009-08-30: the reason we had been
storing oldest-database name, not OID, in ShmemVariableCache was of course
to avoid having to do a catalog lookup at times when it might be unsafe.
This error explains why Aleksandr Dushein is having trouble getting out of
an XID wraparound state in bug #5718, though not how he got into that state
in the first place. I suspect pg_upgrade is at fault there.
This call was present in the aboriginal code from Berkeley, and has
never been touched; it may very well be that it was there to mask
effects of bugs in other places and it may no longer be necessary.
The removal has been foreseen in a code comment since 2007; this seems
to be a good time to test this hypothesis.
new WAL arrives via streaming replication. This reduces the latency, and
also allows us to use a longer polling interval, which is good for energy
efficiency.
We still need to poll to check for the appearance of a trigger file, but
the interval is now 5 seconds (instead of 100ms), like when waiting for
a new WAL segment to appear in WAL archive.
wait until it is set. Latches can be used to reliably wait until a signal
arrives, which is hard otherwise because signals don't interrupt select()
on some platforms, and even when they do, there's race conditions.
On Unix, latches use the so called self-pipe trick under the covers to
implement the sleep until the latch is set, without race conditions. On
Windows, Windows events are used.
Use the new latch abstraction to sleep in walsender, so that as soon as
a transaction finishes, walsender is woken up to immediately send the WAL
to the standby. This reduces the latency between master and standby, which
is good.
Preliminary work by Fujii Masao. The latch implementation is by me, with
helpful comments from many people.
initialize the rd_backend field of a fake Relation entry correctly.
Fortunately, that is easy, since only non-temp relations should ever be
mentioned in the WAL stream.
This allows us to reliably remove all leftover temporary relation
files on cluster startup without reference to system catalogs or WAL;
therefore, we no longer include temporary relations in XLOG_XACT_COMMIT
and XLOG_XACT_ABORT WAL records.
Since these changes require including a backend ID in each
SharedInvalSmgrMsg, the size of the SharedInvalidationMessage.id
field has been reduced from two bytes to one, and the maximum number
of connections has been reduced from INT_MAX / 4 to 2^23-1. It would
be possible to remove these restrictions by increasing the size of
SharedInvalidationMessage by 4 bytes, but right now that doesn't seem
like a good trade-off.
Review by Jaime Casanova and Tom Lane.
Since the only purpose of WAL-loggin SharedInvalidationMessages is to support
Hot Standby operation, they needn't be included when wal_level < hot_standby.
Back-patch to 9.0.
Review by Heikki Linnakanagas and Fujii Masao.
Transaction aborts now record their LSN to avoid corner case
behaviour in SR/HS, hence change of name of variables and functions.
As pointed out by Fujii Masao. Cosmetic changes only.
idea from the start since the variable is only meant to track commit/abort
events. This patch reverts the logic around the variable to what it was in
8.4, except that the value is now kept in shared memory rather than a static
variable, so that it can be reported correctly by CreateRestartPoint (which is
executed in the bgwriter).
max_standby_streaming_delay, and revise the implementation to avoid assuming
that timestamps found in WAL records can meaningfully be compared to clock
time on the standby server. Instead, the delay limits are compared to the
elapsed time since we last obtained a new WAL segment from archive or since
we were last "caught up" to WAL data arriving via streaming replication.
This avoids problems with clock skew between primary and standby, as well
as other corner cases that the original coding would misbehave in, such
as the primary server having significant idle time between transactions.
Per my complaint some time ago and considerable ensuing discussion.
Do some desultory editing on the hot standby documentation, too.
master. Otherwise a subsequent crash could cause the master to lose WAL that
has already been applied on the slave, resulting in the slave being out of
sync and soon corrupt. Per recent discussion and an example from Robert Haas.
Fujii Masao
and retry. If the record is genuinely corrupt in the master database,
there's little hope of recovering, but it's better than simply retrying
to apply the corrupt WAL record in a tight loop without even trying to
retransmit it, which is what we used to do.
pg_last_xlog_replay_location(). Per Robert Haas's suggestion, after
Itagaki Takahiro pointed out an issue in the docs. Also, some wording
changes in the docs by me.
checkpoint_timeout to trigger restartpoints. We used to deliberately only
do time-based restartpoints, because if checkpoint_segments is small we
would spend time doing restartpoints more often than really necessary.
But now that restartpoints are done in bgwriter, they're not as
disruptive as they used to be. Secondly, because streaming replication
stores the streamed WAL files in pg_xlog, we want to clean it up more
often to avoid running out of disk space when checkpoint_timeout is large
and checkpoint_segments small.
Patch by Fujii Masao, with some minor changes by me.
the current one. Not doing this would leave the walwriter with a handle to a
deleted file if there was nothing for it to do for a long period of time,
preventing the file from being completely removed.
Reported by Tollef Fog Heen, and thanks to Heikki for some hand-holding with
the patch.
so simply leads to data waiting in wal_buffers which then causes
later commits to potentially do emergency writes and for all forms
of replication to be potentially delayed without need or benefit.
Issue pointed out exactly by Fujii Masao, following bug report
by Robert Haas on a separate though related topic.
of requirements and documentation on LogStandbySnapshot(). Fixes
two minor bugs reported by Tom Lane that would lead to an incorrect
snapshot after transaction wraparound. Also fix two other problems
discovered that would give incorrect snapshots in certain cases.
ProcArrayApplyRecoveryInfo() substantially rewritten. Some minor
refactoring of xact_redo_apply() and ExpireTreeKnownAssignedTransactionIds().
minRecoveryPoint in control file when replaying a parameter change record,
to ensure that we don't allow hot standby on WAL generated without
wal_level='hot_standby' after a standby restart.
MaxStandbyDelay. Use the GUC units mechanism for the value, and choose more
appropriate timestamp functions for performing tests with it. Make the
ps_activity manipulation in ResolveRecoveryConflictWithVirtualXIDs have
behavior similar to ps_activity code elsewhere, notably not updating the
display when update_process_title is off and not truncating the display
contents at an arbitrarily-chosen length. Improve the docs to be explicit
about what MaxStandbyDelay actually measures, viz the difference between
primary and standby servers' clocks, and the possible hazards if their clocks
aren't in sync.
to perform a backup without archive_mode being enabled. This gives up some
user-error protection in order to improve usefulness for streaming-replication
scenarios. Per discussion.
confusion with streaming-replication settings. Also, change its default
value to "off", because of concern about executing new and poorly-tested
code during ordinary non-replicating operation. Per discussion.
In passing do some minor editing of related documentation.
rather than returning NULL for some-but-not-all failures as they used to.
Remove now-redundant tests for NULL from call sites.
We had to do something about this because many call sites were failing to
check for NULL; and changing it like this seems a lot more useful and
mistake-proof than adding checks to the call sites without them.
archival or hot standby should be WAL-logged, instead of deducing that from
other options like archive_mode. This replaces recovery_connections GUC in
the primary, where it now has no effect, but it's still used in the standby
to enable/disable hot standby.
Remove the WAL-logging of "unlogged operations", like creating an index
without WAL-logging and fsyncing it at the end. Instead, we keep a copy of
the wal_mode setting and the settings that affect how much shared memory a
hot standby server needs to track master transactions (max_connections,
max_prepared_xacts, max_locks_per_xact) in pg_control. Whenever the settings
change, at server restart, write a WAL record noting the new settings and
update pg_control. This allows us to notice the change in those settings in
the standby at the right moment, they used to be included in checkpoint
records, but that meant that a changed value was not reflected in the
standby until the first checkpoint after the change.
Bump PG_CONTROL_VERSION and XLOG_PAGE_MAGIC. Whack XLOG_PAGE_MAGIC back to
the sequence it used to follow, before hot standby and subsequent patches
changed it to 0x9003.
and be more tense about the locking requirements for it, to improve performance
in Hot Standby mode. In passing fix a few bugs and improve a number of
comments in the existing HS code.
Simon Riggs, with some editorialization by Tom
in WAL recovery when it sees the shutdown checkpoint record. It's more
user-friendly to find out about it at that point than at the end of
recovery, and you're not left wondering why your hot standby server never
opens up for read-only connections.
of parameters. Fix bug report by Robert Haas that error message and
hint was incorrect if wrong mode parameters specified on master.
Internal changes only. Proposals for parameter simplification on
master/primary still under way.
Also, make the name of the GUC and the name of the backing variable match.
Alnong the way, clean up a couple of slight typographical errors in the
related docs.
Now doesn't report it is waiting until it actually is waiting,
plus message doesn't appear until at least 5 seconds wait, so
we avoid reporting the wait before we've given the archiver
a reasonable time to wake up and archive the file we just
created earlier in the function.
Also add new unconditional message to confirm safe completion.
Now a normal, healthy execution does not report waiting at
all, just safe completion.
through normal backends. Makes code clearer also, since we
avoid various Assert()s. Performance of snapshots taken
during recovery no longer depends upon number of read-only
backends.
after actually removing one, so that if we can't remove segments because
WAL archiving is lagging behind, we don't unnecessarily forbid streaming
the old not-yet-archived segments that are still perfectly valid. Per
suggestion from Fujii Masao.
doesn't take into account how far the WAL senders are. This way a hung
WAL sender doesn't prevent old WAL segments from being recycled/removed
in the primary, ultimately causing the disk to fill up. Instead add
standby_keep_segments setting to control how many old WAL segments are
kept in the primary. This also makes it more reliable to use streaming
replication without WAL archiving, assuming that you set
standby_keep_segments high enough.
recovery. We might want to relax this in the future, but ThisTimeLineID
isn't currently correct in backends during recovery, so the filename
returned was wrong.
This allows us to see what mode the server is in before it starts to
perform actions that can block or hang. Otherwise server messages
may not appear until after messages that say FATAL the database
server is starting up.
The error message now makes explicit reference to the GUC that must be changed
to fix the problem, using wording suggested by Tom Lane. Along the way,
rename the GUC from MaxWalSenders to max_wal_senders for consistency and
grep-ability.
pg_xlog directory. This is essential for replaying WAL records that
were streamed from the master, after a standby server restart.
If a corrupt record is seen in a file restored from the archive or
streamed from the master, log it as a WARNING and keep retrying. If the
corruption is permanent, and not just a glitch in the whatever copies the
files to the archive or a network error not caught by CRC checks in TCP
for example, we will keep retrying and logging the WARNING indefinitely.
But that's better than shutting down completely, the standby is still
useful for running read-only queries. In PITR the recovery ends at such a
corrupt record, which is a bit questionable, but that's the behavior we
had in previous releases and we don't feel like chaning it now. It does
make sense for tools like pg_standby.
example to 'on or 'off' rather than 'true' or 'false', as shown
in docs. Add restartpoint_command. Add section header for recovery
target parameters, matching docs.
present since 8.0 was never fully meaningful, since two recovery targets
cannot be specified. Refactor recovery target type to make this change
and associated code easier to understand. No change in function.
Bug report arising from internal support question.
in recovery_end_command, it always came out as 0 because InRedo was
cleared before recovery_end_command was executed. Also, always take
ControlFileLock when reading checkpoint location for %r.
The recovery_end_command bug and the missing locking was present in 8.4
as well, that part of this patch will be backported separately.
instead of an exclusive lock.
The change is almost for code cleanup. Since there seems to be no
performance benefits from it, backports should not be needed.
Fujii Masao
Add some checks that seem logically necessary, in particular let's make
real sure that HS slave sessions cannot create temp tables. (If they did
they would think that temp tables belonging to the master's session with
the same BackendId were theirs. We *must* not allow myTempNamespace to
become set in a slave session.)
Change setval() and nextval() so that they are only allowed on temp sequences
in a read-only transaction. This seems consistent with what we allow for
table modifications in read-only transactions. Since an HS slave can't have a
temp sequence, this also provides a nicer cure for the setval PANIC reported
by Erik Rijkers.
Make the error messages more uniform, and have them mention the specific
command being complained of. This seems worth the trifling amount of extra
code, since people are likely to see such messages a lot more than before.
enabled. Bypassing the kernel cache is counter-productive in that case,
because the archiver/walsender process will read from the WAL file
soon after it's written, and if it's not cached the read will cause
a physical read, eating I/O bandwidth available on the WAL drive.
Also, walreceiver process does unaligned writes, so disable O_DIRECT
in walreceiver process for that reason too.
segment of XLOG_BACKUP_END record even if the the record is placed
at a segment boundary. Furthermore the previous implementation could
return nonexistent segment file name when the boundary is in segments
that has "FE" suffix; We never use segments with "FF" suffix.
Backpatch to 8.0, where hot backup was introduced.
Reported by Fujii Masao.
all the values derived from oldestXid, not just that field. Brain fade in
one of my patches associated with flat file removal, exposed by a report
from Fujii Masao.
With this change, xidVacLimit should always be valid, so remove a couple of
bits of complexity associated with the previous assumption that sometimes
it wouldn't get set right away.
In addition, add support for a "payload" string to be passed along with
each notify event.
This implementation should be significantly more efficient than the old one,
and is also more compatible with Hot Standby usage. There is not yet any
facility for HS slaves to receive notifications generated on the master,
although such a thing is possible in future.
Joachim Wieland, reviewed by Jeff Davis; also hacked on by me.
The purpose of this change is to eliminate the need for every caller
of SearchSysCache, SearchSysCacheCopy, SearchSysCacheExists,
GetSysCacheOid, and SearchSysCacheList to know the maximum number
of allowable keys for a syscache entry (currently 4). This will
make it far easier to increase the maximum number of keys in a
future release should we choose to do so, and it makes the code
shorter, too.
Design and review by Tom Lane.
where a database has a non-default tablespaceid. Pass thru MyDatabaseId
and MyDatabaseTableSpace to allow file path to be re-created in
standby and correct invalidation to take place in all cases.
Update and rework xact_commit_desc() debug messages.
Bug report from Tom by code inspection. Fix by me.
echo all the recovery.conf options. Don't emit the "initializing
recovery connections" message, which doesn't mean anything to a user.
Remove the "starting archive recovery" message and replace the
"automatic recovery in progress" message with a more informative message
saying whether the server is doing PITR, normal archive recovery, or
standby mode.
a partial WAL file, assume it's because the file is just being copied to
the archive and treat it the same as "file not found" in standby mode.
pg_standby has a similar check, so it seems reasonable to have the same
level of protection in the built-in standby mode.
restoring from archive, the last WAL segment is not necessarily open at
the end of recovery. Fix assertion that assumed that.
Fujii Masao, fixing the assertion failure reported by Martin Pihlak.
Move rd_targblock, rd_fsm_nblocks, and rd_vm_nblocks from relcache to the smgr
relation entries, so that they will get reset to InvalidBlockNumber whenever
an smgr-level flush happens. Because we now send smgr invalidation messages
immediately (not at end of transaction) when a relation truncation occurs,
this ensures that other backends will reset their values before they next
access the relation. We no longer need the unreliable assumption that a
VACUUM that's doing a truncation will hold its AccessExclusive lock until
commit --- in fact, we can intentionally release that lock as soon as we've
completed the truncation. This patch therefore reverts (most of) Alvaro's
patch of 2009-11-10, as well as my marginal hacking on it yesterday. We can
also get rid of assorted no-longer-needed relcache flushes, which are far more
expensive than an smgr flush because they kill a lot more state.
In passing this patch fixes smgr_redo's failure to perform visibility-map
truncation, and cleans up some rather dubious assumptions in freespace.c and
visibilitymap.c about when rd_fsm_nblocks and rd_vm_nblocks can be out of
date.
recovery. It's zeroed out whenever a checkpoint is written, so the only
scenario where the removed code did anything is when you kill archive
recovery, remove recovery.conf, and start up the server, so that it goes
into crash recovery instead. That's a "don't do that" scenario, but it
seems better to not clear minRecoveryPoint but instead update it like we
do in archive recovery, which is what will now happen.
VACUUM FULL INPLACE), along with a boatload of subsidiary code and complexity.
Per discussion, the use case for this method of vacuuming is no longer large
enough to justify maintaining it; not to mention that we don't wish to invest
the work that would be needed to make it play nicely with Hot Standby.
Aside from the code directly related to old-style VACUUM FULL, this commit
removes support for certain WAL record types that could only be generated
within VACUUM FULL, redirect-pointer removal in heap_page_prune, and
nontransactional generation of cache invalidation sinval messages (the last
being the sticking point for Hot Standby).
We still have to retain all code that copes with finding HEAP_MOVED_OFF and
HEAP_MOVED_IN flag bits on existing tuples. This can't be removed as long
as we want to support in-place update from pre-9.0 databases.
of shared or nailed system catalogs. This has two key benefits:
* The new CLUSTER-based VACUUM FULL can be applied safely to all catalogs.
* We no longer have to use an unsafe reindex-in-place approach for reindexing
shared catalogs.
CLUSTER on nailed catalogs now works too, although I left it disabled on
shared catalogs because the resulting pg_index.indisclustered update would
only be visible in one database.
Since reindexing shared system catalogs is now fully transactional and
crash-safe, the former special cases in REINDEX behavior have been removed;
shared catalogs are treated the same as non-shared.
This commit does not do anything about the recently-discussed problem of
deadlocks between VACUUM FULL/CLUSTER on a system catalog and other
concurrent queries; will address that in a separate patch. As a stopgap,
parallel_schedule has been tweaked to run vacuum.sql by itself, to avoid
such failures during the regression tests.
false positives during Hot Standby conflict processing. Simple
patch to enhance conflict processing, following previous discussions.
Controlled by parameter minimize_standby_conflicts = on | off, with
default off allows measurement of performance impact to see whether
it should be set on all the time.
LogwrtRqst.Write can be set to non-existent FF log segment, we mustn't
try to send that in XLogSend().
Also fix similar bug in ReadRecord(), which I just introduced in the
ReadRecord() refactoring patch.
restore_command, if the connection to the primary server is lost. This
ensures that the standby can recover automatically, if the connection is
lost for a long time and standby falls behind so much that the required
WAL segments have been archived and deleted in the master.
This also makes standby_mode useful without streaming replication; the
server will keep retrying restore_command every few seconds until the
trigger file is found. That's the same basic functionality pg_standby
offers, but without the bells and whistles.
To implement that, refactor the ReadRecord/FetchRecord functions. The
FetchRecord() function introduced in the original streaming replication
patch is removed, and all the retry logic is now in a new function called
XLogReadPage(). XLogReadPage() is now responsible for executing
restore_command, launching walreceiver, and waiting for new WAL to arrive
from primary, as required.
This also changes the life cycle of walreceiver. When launched, it now only
tries to connect to the master once, and exits if the connection fails, or
is lost during streaming for any reason. The startup process detects the
death, and re-launches walreceiver if necessary.
AbortTransaction or AbortSubTransaction, when trying to clean up after an
error that prevented (sub)transaction start from completing:
* access to TopTransactionResourceOwner that might not exist
* assert failure in AtEOXact_GUC, if AtStart_GUC not called yet
* assert failure or core dump in AfterTriggerEndSubXact, if
AfterTriggerBeginSubXact not called yet
Per testing by injecting elog(ERROR) at successive steps in StartTransaction
and StartSubTransaction. It's not clear whether all of these cases could
really occur in the field, but at least one of them is easily exposed by
simple stress testing, as per my accidental discovery yesterday.
woken by alarm we send SIGUSR1 to all backends requesting that they
check to see if they are blocking Startup process. If so, they throw
ERROR/FATAL as for other conflict resolutions. Deadlock stop gap
removed. max_standby_delay = -1 option removed to prevent deadlock.
that would've been WAL-logged if archiving was enabled. If we encounter
such records in archive recovery anyway, we know that some data is
missing from the log. A WARNING is emitted in that case.
Original patch by Fujii Masao, with changes by me.
Conflict reason is passed through directly to the backend, so we can
take decisions about the effect of the conflict based upon the local
state. No specific changes, as yet, though this prepares for later work.
CancelVirtualTransaction() sends signals while holding ProcArrayLock.
Introduce errdetail_abort() to give message detail explaining that the
abort was caused by conflict processing. Remove CONFLICT_MODE states
in favour of using PROCSIG_RECOVERY_CONFLICT states directly, for clarity.
This includes two new kinds of postmaster processes, walsenders and
walreceiver. Walreceiver is responsible for connecting to the primary server
and streaming WAL to disk, while walsender runs in the primary server and
streams WAL from disk to the client.
Documentation still needs work, but the basics are there. We will probably
pull the replication section to a new chapter later on, as well as the
sections describing file-based replication. But let's do that as a separate
patch, so that it's easier to see what has been added/changed. This patch
also adds a new section to the chapter about FE/BE protocol, documenting the
protocol used by walsender/walreceivxer.
Bump catalog version because of two new functions,
pg_last_xlog_receive_location() and pg_last_xlog_replay_location(), for
monitoring the progress of replication.
Fujii Masao, with additional hacking by me
deletion, so that we attempt to unlink the correct filepath. unlink()
errors are ignorable there, so lack of a DatabasePath initialization step
did not cause visible problems until a related bug showed up on Solaris.
Code refactored from xact_redo_commit() to
ProcessCommittedInvalidationMessages() in inval.c. Recovery may replay
shared invalidation messages for many databases, so we cannot
SetDatabasePath() once as we do in normal backends. Read the databaseid
from the shared invalidation messages, then set DatabasePath
temporarily before calling RelationCacheInitFileInvalidate().
Problem report by Robert Treat, analysis and fix by me.
recovery instead of reading the backup history file. This is more robust,
as it stops you from prematurely starting up an inconsisten cluster if the
backup history file is lost for some reason, or if the base backup was
never finished with pg_stop_backup().
This also paves the way for a simpler streaming replication patch, which
doesn't need to care about backup history files anymore.
The backup history file is still created and archived as before, but it's
not used by the system anymore. It's just for informational purposes now.
Bump PG_CONTROL_VERSION as the location of the backup startpoint is now
written to a new field in pg_control, and catversion because initdb is
required
Original patch by Fujii Masao per Simon's idea, with further fixes by me.
Enabled by recovery_connections = on (default) and forcing archive recovery using a recovery.conf. Recovery processing now emulates the original transactions as they are replayed, providing full locking and MVCC behaviour for read only queries. Recovery must enter consistent state before connections are allowed, so there is a delay, typically short, before connections succeed. Replay of recovering transactions can conflict and in some cases deadlock with queries during recovery; these result in query cancellation after max_standby_delay seconds have expired. Infrastructure changes have minor effects on normal running, though introduce four new types of WAL record.
New test mode "make standbycheck" allows regression tests of static command behaviour on a standby server while in recovery. Typical and extreme dynamic behaviours have been checked via code inspection and manual testing. Few port specific behaviours have been utilised, though primary testing has been on Linux only so far.
This commit is the basic patch. Additional changes will follow in this release to enhance some aspects of behaviour, notably improved handling of conflicts, deadlock detection and query cancellation. Changes to VACUUM FULL are also required.
Simon Riggs, with significant and lengthy review by Heikki Linnakangas, including streamlined redesign of snapshot creation and two-phase commit.
Important contributions from Florian Pflug, Mark Kirkwood, Merlin Moncure, Greg Stark, Gianni Ciolli, Gabriele Bartolini, Hannu Krosing, Robert Haas, Tatsuo Ishii, Hiroyuki Yamada plus support and feedback from many other community members.
an allegedly immutable index function. It was previously recognized that
we had to prevent such a function from executing SET/RESET ROLE/SESSION
AUTHORIZATION, or it could trivially obtain the privileges of the session
user. However, since there is in general no privilege checking for changes
of session-local state, it is also possible for such a function to change
settings in a way that might subvert later operations in the same session.
Examples include changing search_path to cause an unexpected function to
be called, or replacing an existing prepared statement with another one
that will execute a function of the attacker's choosing.
The present patch secures VACUUM, ANALYZE, and CREATE INDEX/REINDEX against
these threats, which are the same places previously deemed to need protection
against the SET ROLE issue. GUC changes are still allowed, since there are
many useful cases for that, but we prevent security problems by forcing a
rollback of any GUC change after completing the operation. Other cases are
handled by throwing an error if any change is attempted; these include temp
table creation, closing a cursor, and creating or deleting a prepared
statement. (In 7.4, the infrastructure to roll back GUC changes doesn't
exist, so we settle for rejecting changes of "search_path" in these contexts.)
Original report and patch by Gurjeet Singh, additional analysis by
Tom Lane.
Security: CVE-2009-4136
be part of multixacts, so allocate a slot for each prepared transaction in
the "oldest member" array in multixact.c. On PREPARE TRANSACTION, transfer
the oldest member value from the current backends slot to the prepared xact
slot. Also save and recover the value from the 2pc state file.
The symptom of the bug was that after a transaction prepared, a shared lock
still held by the prepared transaction was sometimes ignored by other
transactions.
Fix back to 8.1, where both 2PC and multixact were introduced.
of checkpoint. Although the checkpoint has been written to WAL at that point
already, so that all data is safe, and we'll retry removing the WAL segment at
the next checkpoint, if such a failure persists we won't be able to remove any
other old WAL segments either and will eventually run out of disk space. It's
better to treat the failure as non-fatal, and move on to clean any other WAL
segment and continue with any other end-of-checkpoint cleanup.
We don't normally expect any such failures, but on Windows it can happen with
some anti-virus or backup software that lock files without FILE_SHARE_DELETE
flag.
Also, the loop in pgrename() to retry when the file is locked was broken. If a
file is locked on Windows, you get ERROR_SHARE_VIOLATION, not
ERROR_ACCESS_DENIED, at least on modern versions. Fix that, although I left
the check for ERROR_ACCESS_DENIED in there as well (presumably it was correct
in some environment), and added ERROR_LOCK_VIOLATION to be consistent with
similar checks in pgwin32_open(). Reduce the timeout on the loop from 30s to
10s, on the grounds that since it's been broken, we've effectively had a
timeout of 0s and no-one has complained, so a smaller timeout is actually
closer to the old behavior. A longer timeout would mean that if recycling a
WAL file fails because it's locked for some reason, InstallXLogFileSegment()
will hold ControlFileLock for longer, potentially blocking other backends, so
a long timeout isn't totally harmless.
While we're at it, set errno correctly in pgrename().
Backpatch to 8.2, which is the oldest version supported on Windows. The xlog.c
changes would make sense on other platforms and thus on older versions as
well, but since there's no such locking issues on other platforms, it's not
worth it.
file handle on it, the file goes into "pending deletion" state where it
still shows up in directory listing, but isn't accessible otherwise. That
confuses RemoveOldXLogFiles(), making it think that the file hasn't been
archived yet, while it actually was, and it was deleted along with the .done
file.
Fix that by renaming the file with ".deleted" extension before deleting it.
Also check the return value of rename() and unlink(), so that if the removal
fails for any reason (e.g another process is holding the file locked), we
don't delete the .done file until the WAL file is really gone.
Backpatch to 8.2, which is the oldest version supported on Windows.
own database's datfrozenxid, if the current value is old enough to be
forcing autovacuums or warning messages. This ensures that a bogus
value is replaced as soon as possible. Per a comment from Heikki.
Recent commits have removed the various uses it was supporting. It was a
performance bottleneck, according to bug report #4919 by Lauris Ulmanis; seems
it slowed down user creation after a billion users.
XID) in checkpoint records. This eliminates the need to recompute the value
from scratch during database startup, which is one of the two remaining
reasons for the flatfile code to exist. It should also simplify life for
hot-standby operation.
To avoid bloating the checkpoint records unreasonably, I switched from
tracking the oldest database by name to tracking it by OID. This turns
out to save cycles in general (everywhere but the warning-generating
paths, which we hardly care about) and also helps us deal with the case
that the oldest database got dropped instead of being vacuumed. The prior
coding might go for a long time without updating the wrap limit in that case,
which is bad because it might result in a lot of useless autovacuum activity.
was incorrectly initialized with timeline ID 0. That rendered the WAL page
unrecoverable, making a subsequent archive recovery stop at that point.
ThisTimeLineID needs to be initialized before calling AdvanceXLInsertBuffer().
This fixes bug #5011 reported by James Bardin. Backpatch to 8.4, as the bug
was introduced by the changes to use of bgwriter for writing the
end-of-archive-recovery checkpoint. Patch by Tom Lane.
To make this work in the base case, pg_database now has a nailed-in-cache
relation descriptor that is initialized using hardwired knowledge in
relcache.c. This means pg_database is added to the set of relations that
need to have a Schema_pg_xxx macro maintained in pg_attribute.h. When this
path is taken, we'll have to do a seqscan of pg_database to find the row
we need.
In the normal case, we are able to do an indexscan to find the database's row
by name. This is made possible by storing a global relcache init file that
describes only the shared catalogs and their indexes (and therefore is usable
by all backends in any database). A new backend loads this cache file,
finds its database OID after an indexscan on pg_database, and then loads
the local relcache init file for that database.
This change should effectively eliminate number of databases as a factor
in backend startup time, even with large numbers of databases. However,
the real reason for doing it is as a first step towards getting rid of
the flat files altogether. There are still several other sub-projects
to be tackled before that can happen.
archive recovery. Invent a separate state variable and inquiry function
for XLogInsertAllowed() to clarify some tests and make the management of
writing the end-of-recovery checkpoint less klugy. Fix several places
that were incorrectly testing InRecovery when they should be looking at
RecoveryInProgress or XLogInsertAllowed (because they will now be executed
in the bgwriter not startup process). Clarify handling of bad LSNs passed
to XLogFlush during recovery. Use a spinlock for setting/testing
SharedRecoveryInProgress. Improve quite a lot of comments.
Heikki and Tom
during it:
When bgwriter is active, the startup process can't perform mdsync() correctly
because it won't see the fsync requests accumulated in bgwriter's private
pendingOpsTable. Therefore make bgwriter responsible for the end-of-recovery
checkpoint as well, when it's active.
When bgwriter is active (= archive recovery), the startup process must not
accumulate fsync requests to its own pendingOpsTable, since bgwriter won't
see them there when it performs restartpoints. Make startup process drop its
pendingOpsTable when bgwriter is launched to avoid that.
Update minimum recovery point one last time when leaving archive recovery.
It won't be updated by the end-of-recovery checkpoint because XLogFlush()
sees us as out of recovery already.
This fixes bug #4879 reported by Fujii Masao.
acting like runs inside WAL recovery, but it doesn't. I must've copy-pasted
this from a redo-function in the relation forks patch. Noticed by Tom Lane
while he was looking through callers of smgrdounlink().
symbolic links with the -l option, and as Fujii Masao pointed out we ended up
overwriting files in the archive directory before this patch. Patch by
Aidan Van Dyk, Fujii Masao and me.
Backpatch to 8.3, where pg_standby was introduced.
copies?) to ensure they really don't run proc_exit/shmem_exit callbacks,
as was intended. I broke this behavior recently by installing atexit
callbacks without thinking about the one case where we truly don't want
to run those callback functions. Noted in an example from Dave Page.
is run at the end of archive recovery, providing a chance to do external
cleanup. Modify pg_standby so that it no longer removes the trigger file,
that is to be done using the recovery_end_command now.
Provide a "smart" failover mode in pg_standby, where we don't fail over
immediately, but only after recovering all unapplied WAL from the archive.
That gives you zero data loss assuming all WAL was archived before
failover, which is what most users of pg_standby actually want.
recovery_end_command by Simon Riggs, pg_standby changes by Fujii Masao and
myself.
redirecting libxml's allocations into a Postgres context. Instead, just let
it use malloc directly, and add PG_TRY blocks as needed to be sure we release
libxml data structures in error recovery code paths. This is ugly but seems
much more likely to play nicely with third-party uses of libxml, as seen in
recent trouble reports about using Perl XML facilities in pl/perl and bug
#4774 about contrib/xml2.
I left the code for allocation redirection in place, but it's only
built/used if you #define USE_LIBXMLCONTEXT. This is because I found it
useful to corral libxml's allocations in a palloc context when hunting
for libxml memory leaks, and we're surely going to have more of those
in the future with this type of approach. But we don't want it turned on
in a normal build because it breaks exactly what we need to fix.
I have not re-indented most of the code sections that are now wrapped
by PG_TRY(); that's for ease of review. pg_indent will fix it.
This is a pre-existing bug in 8.3, but I don't dare back-patch this change
until it's gotten a reasonable amount of field testing.
you can end up with an unrecoverable backup if you start a new base backup
right after finishing archive recovery. In that scenario, the redo pointer of
the checkpoint that pg_start_backup() writes points to the XLOG segment where
the timeline-changing end-of-archive-recovery checkpoint is. The beginning
of that segment contains pages with the old timeline ID, and we don't accept
that in recovery unless we find a history file covering the old timeline ID.
If you omit pg_xlog from the base backup and clear the archive directory
before starting the backup, there will be no such history file available.
The bug is present in all versions since PITR was introduced in 8.0, but I'm
back-patching only back to 8.2. Earlier versions didn't have XLOG switch
records, making this fix unfeasible. Given the lack of reports until now,
it doesn't seem worthwhile to spend more effort to fix 8.0 and 8.1.
Per report and suggestion by Mikael Krantz
documentation warnings against setting it nonzero unless active use of
prepared transactions is intended and a suitable transaction manager has been
installed. This should help to prevent the type of scenario we've seen
several times now where a prepared transaction is forgotten and eventually
causes severe maintenance problems (or even anti-wraparound shutdown).
The only real reason we had the default be nonzero in the first place was to
support regression testing of the feature. To still be able to do that,
tweak pg_regress to force a nonzero value during "make check". Since we
cannot force a nonzero value in "make installcheck", add a variant regression
test "expected" file that shows the results that will be obtained when
max_prepared_transactions is zero.
Also, extend the HINT messages for transaction wraparound warnings to mention
the possibility that old prepared transactions are causing the problem.
All per today's discussion.
the checkpoint in immediate or lazy mode. This is to address complaints
that pg_start_backup() takes a long time even when there's no need to minimize
its I/O consumption.
some bufmgr probes, take out redundant and memory-leak-inducing path arguments
to smgr__md__read__done and smgr__md__write__done, fix bogus attempt to
recalculate space used in sort__done, clean up formatting in places where
I'm not sure pgindent will do a nice job by itself.
its usual buffer cleaning duties during archive recovery, and it's responsible
for performing restartpoints.
This requires some changes in postmaster. When the startup process has done
all the initialization and is ready to start WAL redo, it signals the
postmaster to launch the background writer. The postmaster is signaled again
when the point in recovery is reached where we know that the database is in
consistent state. Postmaster isn't interested in that at the moment, but
that's the point where we could let other backends in to perform read-only
queries. The postmaster is signaled third time when the recovery has ended,
so that postmaster knows that it's safe to start accepting connections.
The startup process now traps SIGTERM, and performs a "clean" shutdown. If
you do a fast shutdown during recovery, a shutdown restartpoint is performed,
like a shutdown checkpoint, and postmaster kills the processes cleanly. You
still have to continue the recovery at next startup, though.
Currently, the background writer is only launched during archive recovery.
We could launch it during crash recovery as well, but it seems better to keep
that codepath as simple as possible, for the sake of robustness. And it
couldn't do any restartpoints during crash recovery anyway, so it wouldn't be
that useful.
log_restartpoints is gone. Use log_checkpoints instead. This is yet to be
documented.
This whole operation is a pre-requisite for Hot Standby, but has some value of
its own whether the hot standby patch makes 8.4 or not.
Simon Riggs, with lots of modifications by me.
be used instead of the normal exclusive lock, and make WAL redo functions
responsible for calling RestoreBkpBlocks(). They know better what kind of a
lock they need.
At the moment, this just moves things around with no functional change, but
makes the hot standby patch that's under review cleaner.
we can get some buildfarm feedback about whether that function is still
problematic. (Note that the planned async-preread patch will not really
prove anything one way or the other in buildfarm testing, since it will
be inactive with default GUC settings.)
includes a few new ones.
- Fixed compilation errors on OS X for probes that use typedefs
- Fixed a number of probes to pass ForkNumber per the relation forks
patch
- The new probes are those that were taken out from the previous
submitted patch and required simple fixes. Will submit the other probes
that may require more discussion in a separate patch.
Robert Lor
vacuuming (it's not), say "database-wide VACUUM" instead of "full-database
VACUUM" in the relevant hint messages. Also, document the permissions needed
to do this. Per today's discussion.
