There's three categories of changes leading to better performance:
- Splitting the per-attribute part of SendRowDescriptionMessage into a
v2 and a v3 version allows avoiding branches for every attribute.
- Preallocating the size of the buffer to be big enough for all
attributes and then using pq_write* avoids unnecessary buffer
size checks & resizing.
- Reusing a persistently allocated StringInfo for all
SendRowDescriptionMessage() invocations avoids repeated allocations
& reallocations.
Author: Andres Freund
Discussion: https://postgr.es/m/20170914063418.sckdzgjfrsbekae4@alap3.anarazel.de
This avoids newly allocating, and then possibly growing, the
stringbuffer for every row. For wide rows this can substantially
reduce memory allocator overhead, at the price of not immediately
reducing memory usage after outputting an especially wide row.
Author: Andres Freund
Discussion: https://postgr.es/m/20170914063418.sckdzgjfrsbekae4@alap3.anarazel.de
resowner/README contained advice to use a PG_TRY block to restore the
old CurrentResourceOwner value anywhere that that variable is transiently
changed. That advice was only inconsistently followed, however, and
on reflection it seems like unnecessary overhead. We don't bother
with such a convention for transient CurrentMemoryContext changes,
on the grounds that any (sub)transaction abort will start out by
resetting CurrentMemoryContext to what it wants. But the same is
true of CurrentResourceOwner, so there seems no need to treat it
differently.
Hence, remove PG_TRY blocks that exist only to restore CurrentResourceOwner
before re-throwing the error. There are a couple of places that restore
it along with some other actions, and I left those alone; the restore is
probably unnecessary but no noticeable gain will result from removing it.
Discussion: https://postgr.es/m/5236.1507583529@sss.pgh.pa.us
Sloppy loop coding in set_status_by_pages() resulted in fetching one array
element more than it should from the subxids[] array. The odds of this
resulting in SIGSEGV are pretty small, but we've certainly seen that happen
with similar mistakes elsewhere. While at it, we can get rid of an extra
TransactionIdToPage() calculation per loop.
Per report from David Binderman. Back-patch to all supported branches,
since this code is quite old.
Discussion: https://postgr.es/m/HE1PR0802MB2331CBA919CBFFF0C465EB429C710@HE1PR0802MB2331.eurprd08.prod.outlook.com
When some tuple versions in an update chain are frozen due to them being
older than freeze_min_age, the xmax/xmin trail can become broken. This
breaks HOT (and probably other things). A subsequent VACUUM can break
things in more serious ways, such as leaving orphan heap-only tuples
whose root HOT redirect items were removed. This can be seen because
index creation (or REINDEX) complain like
ERROR: XX000: failed to find parent tuple for heap-only tuple at (0,7) in table "t"
Because of relfrozenxid contraints, we cannot avoid the freezing of the
early tuples, so we must cope with the results: whenever we see an Xmin
of FrozenTransactionId, consider it a match for whatever the previous
Xmax value was.
This problem seems to have appeared in 9.3 with multixact changes,
though strictly speaking it seems unrelated.
Since 9.4 we have commit 37484ad2a "Change the way we mark tuples as
frozen", so the fix is simple: just compare the raw Xmin (still stored
in the tuple header, since freezing merely set an infomask bit) to the
Xmax. But in 9.3 we rewrite the Xmin value to FrozenTransactionId, so
the original value is lost and we have nothing to compare the Xmax with.
To cope with that case we need to compare the Xmin with FrozenXid,
assume it's a match, and hope for the best. Sadly, since you can
pg_upgrade a 9.3 instance containing half-frozen pages to newer
releases, we need to keep the old check in newer versions too, which
seems a bit brittle; I hope we can somehow get rid of that.
I didn't optimize the new function for performance. The new coding is
probably a bit slower than before, since there is a function call rather
than a straight comparison, but I'd rather have it work correctly than
be fast but wrong.
This is a followup after 20b6552242 fixed a few related problems.
Apparently, in 9.6 and up there are more ways to get into trouble, but
in 9.3 - 9.5 I cannot reproduce a problem anymore with this patch, so
there must be a separate bug.
Reported-by: Peter Geoghegan
Diagnosed-by: Peter Geoghegan, Michael Paquier, Daniel Wood,
Yi Wen Wong, Álvaro
Discussion: https://postgr.es/m/CAH2-Wznm4rCrhFAiwKPWTpEw2bXDtgROZK7jWWGucXeH3D1fmA@mail.gmail.com
Haribabu Kommi, reviewed by Dilip Kumar and Rafia Sabih. Various
cosmetic changes by me to explain why this appears to be safe but
allowing inserts in parallel mode in general wouldn't be. Also, I
removed the REFRESH MATERIALIZED VIEW case from Haribabu's patch,
since I'm not convinced that case is OK, and hacked on the
documentation somewhat.
Discussion: http://postgr.es/m/CAJrrPGdo5bak6qnPWe8Kpi8g_jfQEs-G4SYmG9y+OFaw2-dPvA@mail.gmail.com
Add bgw_type field to background worker structure. It is intended to be
set to the same value for all workers of the same type, so they can be
grouped in pg_stat_activity, for example.
The backend_type column in pg_stat_activity now shows bgw_type for a
background worker. The ps listing also no longer calls out that a
process is a background worker but just show the bgw_type. That way,
being a background worker is more of an implementation detail now that
is not shown to the user. However, most log messages still refer to
'background worker "%s"'; otherwise constructing sensible and
translatable log messages would become tricky.
Reviewed-by: Michael Paquier <michael.paquier@gmail.com>
Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
Vacuum calls page-level HOT prune to remove dead HOT tuples before doing
liveness checks (HeapTupleSatisfiesVacuum) on the remaining tuples. But
concurrent transaction commit/abort may turn DEAD some of the HOT tuples
that survived the prune, before HeapTupleSatisfiesVacuum tests them.
This happens to activate the code that decides to freeze the tuple ...
which resuscitates it, duplicating data.
(This is especially bad if there's any unique constraints, because those
are now internally violated due to the duplicate entries, though you
won't know until you try to REINDEX or dump/restore the table.)
One possible fix would be to simply skip doing anything to the tuple,
and hope that the next HOT prune would remove it. But there is a
problem: if the tuple is older than freeze horizon, this would leave an
unfrozen XID behind, and if no HOT prune happens to clean it up before
the containing pg_clog segment is truncated away, it'd later cause an
error when the XID is looked up.
Fix the problem by having the tuple freezing routines cope with the
situation: don't freeze the tuple (and keep it dead). In the cases that
the XID is older than the freeze age, set the HEAP_XMAX_COMMITTED flag
so that there is no need to look up the XID in pg_clog later on.
An isolation test is included, authored by Michael Paquier, loosely
based on Daniel Wood's original reproducer. It only tests one
particular scenario, though, not all the possible ways for this problem
to surface; it be good to have a more reliable way to test this more
fully, but it'd require more work.
In message https://postgr.es/m/20170911140103.5akxptyrwgpc25bw@alvherre.pgsql
I outlined another test case (more closely matching Dan Wood's) that
exposed a few more ways for the problem to occur.
Backpatch all the way back to 9.3, where this problem was introduced by
multixact juggling. In branches 9.3 and 9.4, this includes a backpatch
of commit e5ff9fefcd50 (of 9.5 era), since the original is not
correctable without matching the coding pattern in 9.5 up.
Reported-by: Daniel Wood
Diagnosed-by: Daniel Wood
Reviewed-by: Yi Wen Wong, Michaël Paquier
Discussion: https://postgr.es/m/E5711E62-8FDF-4DCA-A888-C200BF6B5742@amazon.com
This reverts commit 15bc038f9, along with the followon commits 1635e80d3
and 984c92074 that tried to clean up the problems exposed by bug #14825.
The result was incomplete because it failed to address parallel-query
requirements. With 10.0 release so close upon us, now does not seem like
the time to be adding more code to fix that. I hope we can un-revert this
code and add the missing parallel query support during the v11 cycle.
Back-patch to v10.
Discussion: https://postgr.es/m/20170922185904.1448.16585@wrigleys.postgresql.org
Commit 15bc038f9 allowed ALTER TYPE ADD VALUE to be executed inside
transaction blocks, by disallowing the use of the added value later
in the same transaction, except under limited circumstances. However,
the test for "limited circumstances" was heuristic and could reject
references to enum values that were created during CREATE TYPE AS ENUM,
not just later. This breaks the use-case of restoring pg_dump scripts
in a single transaction, as reported in bug #14825 from Balazs Szilfai.
We can improve this by keeping a "blacklist" table of enum value OIDs
created by ALTER TYPE ADD VALUE during the current transaction. Any
visible-but-uncommitted value whose OID is not in the blacklist must
have been created by CREATE TYPE AS ENUM, and can be used safely
because it could not have a lifespan shorter than its parent enum type.
This change also removes the restriction that a renamed enum value
can't be used before being committed (unless it was on the blacklist).
Andrew Dunstan, with cosmetic improvements by me.
Back-patch to v10.
Discussion: https://postgr.es/m/20170922185904.1448.16585@wrigleys.postgresql.org
This was intended as infrastructure for weakening VACUUM's locking
requirements, similar to what was done for btree indexes in commit
2ed5b87f96. However, for hash indexes,
it seems that the improvements which are possible are actually
extremely marginal. Furthermore, performing the LSN cross-check will
end up skipping cleanup far more often than is necessary; we only care
about page modifications due to a VACUUM, but the LSN check will fail
if ANY modification has occurred. So, rather than pressing forward
with that "optimization", just rip the LSN field out.
Patch by me, reviewed by Ashutosh Sharma and Amit Kapila
Discussion: http://postgr.es/m/CAA4eK1JxqqcuC5Un7YLQVhOYSZBS+t=3xqZuEkt5RyquyuxpwQ@mail.gmail.com
The file handling functions from fd.c were called with a diverse mix of
notations for the file permissions when they were opening new files.
Almost all files created by the server should have the same permissions
set. So change the API so that e.g. OpenTransientFile() automatically
uses the standard permissions set, and OpenTransientFilePerm() is a new
function that takes an explicit permissions set for the few cases where
it is needed. This also saves an unnecessary argument for call sites
that are just opening an existing file.
While we're reviewing these APIs, get rid of the FileName typedef and
use the standard const char * for the file name and mode_t for the file
mode. This makes these functions match other file handling functions
and removes an unnecessary layer of mysteriousness. We can also get rid
of a few casts that way.
Author: David Steele <david@pgmasters.net>
Commit 09cb5c0e7d added a similar
optimization to btree back in 2006, but nobody bothered to implement
the same thing for hash indexes, probably because they weren't
WAL-logged and had lots of other performance problems as well. As
with the corresponding btree case, this eliminates the problem of
potentially needing to refind our position within the page, and cuts
down on pin/unpin traffic as well.
Ashutosh Sharma, reviewed by Alexander Korotkov, Jesper Pedersen,
Amit Kapila, and me. Some final edits to comments and README by
me.
Discussion: http://postgr.es/m/CAE9k0Pm3KTx93K8_5j6VMzG4h5F+SyknxUwXrN-zqSZ9X8ZS3w@mail.gmail.com
For performance reasons a larger segment size than the default 16MB
can be useful. A larger segment size has two main benefits: Firstly,
in setups using archiving, it makes it easier to write scripts that
can keep up with higher amounts of WAL, secondly, the WAL has to be
written and synced to disk less frequently.
But at the same time large segment size are disadvantageous for
smaller databases. So far the segment size had to be configured at
compile time, often making it unrealistic to choose one fitting to a
particularly load. Therefore change it to a initdb time setting.
This includes a breaking changes to the xlogreader.h API, which now
requires the current segment size to be configured. For that and
similar reasons a number of binaries had to be taught how to recognize
the current segment size.
Author: Beena Emerson, editorialized by Andres Freund
Reviewed-By: Andres Freund, David Steele, Kuntal Ghosh, Michael
Paquier, Peter Eisentraut, Robert Hass, Tushar Ahuja
Discussion: https://postgr.es/m/CAOG9ApEAcQ--1ieKbhFzXSQPw_YLmepaa4hNdnY5+ZULpt81Mw@mail.gmail.com
The preceding patch allowed us to remove useless GiST support functions.
This patch actually does that for all the no-op cases in the core GiST
code. This buys us whatever performance gain is to be had, and more
importantly exercises the preceding patch.
There remain no-op functions in the contrib GiST opclasses, but those
will take more work to remove.
Discussion: https://postgr.es/m/CAJEAwVELVx9gYscpE=Be6iJxvdW5unZ_LkcAaVNSeOwvdwtD=A@mail.gmail.com
There are common use-cases in which the compress and/or decompress
functions can be omitted, with the result being that we make no
data transformation when storing or retrieving index values.
Previously, you had to provide a no-op function anyway, but this
patch allows such opclass support functions to be omitted.
Furthermore, if the compress function is omitted, then the core code
knows that the stored representation is the same as the original data.
This means we can allow index-only scans without requiring a fetch
function to be provided either. Previously you had to provide a
no-op fetch function if you wanted IOS to work.
This reportedly provides a small performance benefit in such cases,
but IMO the real reason for doing it is just to reduce the amount of
useless boilerplate code that has to be written for GiST opclasses.
Andrey Borodin, reviewed by Dmitriy Sarafannikov
Discussion: https://postgr.es/m/CAJEAwVELVx9gYscpE=Be6iJxvdW5unZ_LkcAaVNSeOwvdwtD=A@mail.gmail.com
The bug was caused by not re-reading the control file during crash
recovery restarts, which lead to an attempt to pfree() shared memory
contents. The fix is to re-read the control file, which seems good
anyway.
It's unclear as of this moment, whether we want to keep the
refactoring introduced in the commit referenced above, or come up with
an alternative approach. But fixing the bug in the mean time seems
like a good idea regardless.
A followup commit will introduce regression test coverage for crash
restarts.
Reported-By: Tom Lane
Discussion: https://postgr.es/m/14134.1505572349@sss.pgh.pa.us
Make the btree page-flags test macros (P_ISLEAF and friends) return clean
boolean values, rather than values that might not fit in a bool. Use them
in a few places that were randomly referencing the flag bits directly.
In passing, change access/nbtree/'s only direct use of BUFFER_LOCK_SHARE to
BT_READ. (Some think we should go the other way, but as long as we have
BT_READ/BT_WRITE, let's use them consistently.)
Masahiko Sawada, reviewed by Doug Doole
Discussion: https://postgr.es/m/CAD21AoBmWPeN=WBB5Jvyz_Nt3rmW1ebUyAnk3ZbJP3RMXALJog@mail.gmail.com
Tuples can have type RECORDOID and a typmod number that identifies a blessed
TupleDesc in a backend-private cache. To support the sharing of such tuples
through shared memory and temporary files, provide a typmod registry in
shared memory.
To achieve that, introduce per-session DSM segments, created on demand when a
backend first runs a parallel query. The per-session DSM segment has a
table-of-contents just like the per-query DSM segment, and initially the
contents are a shared record typmod registry and a DSA area to provide the
space it needs to grow.
State relating to the current session is accessed via a Session object
reached through global variable CurrentSession that may require significant
redesign further down the road as we figure out what else needs to be shared
or remodelled.
Author: Thomas Munro
Reviewed-By: Andres Freund
Discussion: https://postgr.es/m/CAEepm=0ZtQ-SpsgCyzzYpsXS6e=kZWqk3g5Ygn3MDV7A8dabUA@mail.gmail.com
Previously we read the control file in multiple places. But soon the
segment size will be configurable and stored in the control file, and
that needs to be available earlier than it currently is needed.
Instead of adding yet another place where it's read, refactor things
so there's a single processing of the control file during startup (in
EXEC_BACKEND that's every individual backend's startup).
Author: Andres Freund
Discussion: http://postgr.es/m/20170913092828.aozd3gvvmw67gmyc@alap3.anarazel.de
In commit fccebe421, we hacked get_actual_variable_range() to scan the
index with SnapshotDirty, so that if there are many uncommitted tuples
at the end of the index range, it wouldn't laboriously scan through all
of them looking for a live value to return. However, that didn't fix it
for the case of many recently-dead tuples at the end of the index;
SnapshotDirty recognizes those as committed dead and so we're back to
the same problem.
To improve the situation, invent a "SnapshotNonVacuumable" snapshot type
and use that instead. The reason this helps is that, if the snapshot
rejects a given index entry, we know that the indexscan will mark that
index entry as killed. This means the next get_actual_variable_range()
scan will proceed past that entry without visiting the heap, making the
scan a lot faster. We may end up accepting a recently-dead tuple as
being the estimated extremal value, but that doesn't seem much worse than
the compromise we made before to accept not-yet-committed extremal values.
The cost of the scan is still proportional to the number of dead index
entries at the end of the range, so in the interval after a mass delete
but before VACUUM's cleaned up the mess, it's still possible for
get_actual_variable_range() to take a noticeable amount of time, if you've
got enough such dead entries. But the constant factor is much much better
than before, since all we need to do with each index entry is test its
"killed" bit.
We chose to back-patch commit fccebe421 at the time, but I'm hesitant to
do so here, because this form of the problem seems to affect many fewer
people. Also, even when it happens, it's less bad than the case fixed
by commit fccebe421 because we don't get the contention effects from
expensive TransactionIdIsInProgress tests.
Dmitriy Sarafannikov, reviewed by Andrey Borodin
Discussion: https://postgr.es/m/05C72CF7-B5F6-4DB9-8A09-5AC897653113@yandex.ru
It is equivalent in ANSI C to write (*funcptr) () and funcptr(). These
two styles have been applied inconsistently. After discussion, we'll
use the more verbose style for plain function pointer variables, to make
it clear that it's a variable, and the shorter style when the function
pointer is in a struct (s.func() or s->func()), because then it's clear
that it's not a plain function name, and otherwise the excessive
punctuation makes some of those invocations hard to read.
Discussion: https://www.postgresql.org/message-id/f52c16db-14ed-757d-4b48-7ef360b1631d@2ndquadrant.com
Issuing a savepoint-related command in a Query message that contains
multiple SQL statements led to a FATAL exit with a complaint about
"unexpected state STARTED". This is a shortcoming of commit 4f896dac1,
which attempted to prevent such misbehaviors in multi-statement strings;
its quick hack of marking the individual statements as "not top-level"
does the wrong thing in this case, and isn't a very accurate description
of the situation anyway.
To fix, let's introduce into xact.c an explicit model of what happens for
multi-statement Query strings. This is an "implicit transaction block
in progress" state, which for many purposes works like the normal
TBLOCK_INPROGRESS state --- in particular, IsTransactionBlock returns true,
causing the desired result that PreventTransactionChain will throw error.
But in case of error abort it works like TBLOCK_STARTED, allowing the
transaction to be cancelled without need for an explicit ROLLBACK command.
Commit 4f896dac1 is reverted in toto, so that we go back to treating the
individual statements as "top level". We could have left it as-is, but
this allows sharpening the error message for PreventTransactionChain
calls inside functions.
Except for getting a normal error instead of a FATAL exit for savepoint
commands, this patch should result in no user-visible behavioral change
(other than that one error message rewording). There are some things
we might want to do in the line of changing the appearance or wording of
error and warning messages around this behavior, which would be much
simpler to do now that it's an explicitly modeled state. But I haven't
done them here.
Although this fixes a long-standing bug, no backpatch. The consequences
of the bug don't seem severe enough to justify the risk that this commit
itself creates some new issue.
Patch by me, but it owes something to previous investigation by
Takayuki Tsunakawa, who also reported the bug in the first place.
Also thanks to Michael Paquier for reviewing.
Discussion: https://postgr.es/m/0A3221C70F24FB45833433255569204D1F6BE40D@G01JPEXMBYT05
Commit 0e141c0fbb introduced a mechanism
to reduce contention on ProcArrayLock by having a single process clear
XIDs in the procArray on behalf of multiple processes, reducing the
need to hand the lock around. A previous attempt to introduce a similar
mechanism for CLogControlLock in ccce90b398
crashed and burned, but the design problem which resulted in those
failures is believed to have been corrected in this version.
Amit Kapila, with some cosmetic changes by me. See the previous commit
message for additional credits.
Discussion: http://postgr.es/m/CAA4eK1KudxzgWhuywY_X=yeSAhJMT4DwCjroV5Ay60xaeB2Eew@mail.gmail.com
This will be useful for hash partitioning, which needs a way to seed
the hash functions to avoid problems such as a hash index on a hash
partitioned table clumping all values into a small portion of the
bucket space; it's also useful for anything that wants a 64-bit hash
value rather than a 32-bit hash value.
Just in case somebody wants a 64-bit hash value that is compatible
with the existing 32-bit hash values, make the low 32-bits of the
64-bit hash value match the 32-bit hash value when the seed is 0.
Robert Haas and Amul Sul
Discussion: http://postgr.es/m/CA+Tgmoafx2yoJuhCQQOL5CocEi-w_uG4S2xT0EtgiJnPGcHW3g@mail.gmail.com
The logic around shm_mq_detach was a few bricks shy of a load, because
(contrary to the comments for shm_mq_attach) all it did was update the
shared shm_mq state. That left us leaking a bit of process-local
memory, but much worse, the on_dsm_detach callback for shm_mq_detach
was still armed. That means that whenever we ultimately detach from
the DSM segment, we'd run shm_mq_detach again for already-detached,
possibly long-dead queues. This accidentally fails to fail today,
because we only ever re-use a shm_mq's memory for another shm_mq, and
multiple detach attempts on the last such shm_mq are fairly harmless.
But it's gonna bite us someday, so let's clean it up.
To do that, change shm_mq_detach's API so it takes a shm_mq_handle
not the underlying shm_mq. This makes the callers simpler in most
cases anyway. Also fix a few places in parallel.c that were just
pfree'ing the handle structs rather than doing proper cleanup.
Back-patch to v10 because of the risk that the revenant shm_mq_detach
callbacks would cause a live bug sometime. Since this is an API
change, it's too late to do it in 9.6. (We could make a variant
patch that preserves API, but I'm not excited enough to do that.)
Discussion: https://postgr.es/m/8670.1504192177@sss.pgh.pa.us
Previously, the parallel executor logic did reinitialization of shared
state within the ExecReScan code for parallel-aware scan nodes. This is
problematic, because it means that the ExecReScan call has to occur
synchronously (ie, during the parent Gather node's ReScan call). That is
swimming very much against the tide so far as the ExecReScan machinery is
concerned; the fact that it works at all today depends on a lot of fragile
assumptions, such as that no plan node between Gather and a parallel-aware
scan node is parameterized. Another objection is that because ExecReScan
might be called in workers as well as the leader, hacky extra tests are
needed in some places to prevent unwanted shared-state resets.
Hence, let's separate this code into two functions, a ReInitializeDSM
call and the ReScan call proper. ReInitializeDSM is called only in
the leader and is guaranteed to run before we start new workers.
ReScan is returned to its traditional function of resetting only local
state, which means that ExecReScan's usual habits of delaying or
eliminating child rescan calls are safe again.
As with the preceding commit 7df2c1f8d, it doesn't seem to be necessary
to make these changes in 9.6, which is a good thing because the FDW and
CustomScan APIs are impacted.
Discussion: https://postgr.es/m/CAA4eK1JkByysFJNh9M349u_nNjqETuEnY_y1VUc_kJiU0bxtaQ@mail.gmail.com
Previously, tuple descriptors were stored in chains keyed by a fixed size
array of OIDs. That meant there were effectively two levels of collision
chain -- one inside and one outside the hash table. Instead, let dynahash.c
look after conflicts for us by supplying a proper hash and equal function
pair.
This is a nice cleanup on its own, but also simplifies followup
changes allowing blessed TupleDescs to be shared between backends
participating in parallel query.
Author: Thomas Munro
Reviewed-By: Andres Freund
Discussion: https://postgr.es/m/CAEepm%3D34GVhOL%2BarUx56yx7OPk7%3DqpGsv3CpO54feqjAwQKm5g%40mail.gmail.com
TupleDesc's attributes were already stored in contiguous memory after the
struct. Go one step further and get rid of the array of pointers to
attributes so that they can be stored in shared memory mapped at different
addresses in each backend. This won't work for TupleDescs with contraints
and defaults, since those point to other objects, but for many purposes
only attributes are needed.
Author: Thomas Munro
Reviewed-By: Andres Freund
Discussion: https://postgr.es/m/CAEepm=0ZtQ-SpsgCyzzYpsXS6e=kZWqk3g5Ygn3MDV7A8dabUA@mail.gmail.com
This is a mechanical change in preparation for a later commit that
will change the layout of TupleDesc. Introducing a macro to abstract
the details of where attributes are stored will allow us to change
that in separate step and revise it in future.
Author: Thomas Munro, editorialized by Andres Freund
Reviewed-By: Andres Freund
Discussion: https://postgr.es/m/CAEepm=0ZtQ-SpsgCyzzYpsXS6e=kZWqk3g5Ygn3MDV7A8dabUA@mail.gmail.com
As Andres pointed out, pg_atomic_init_u64 must be used to initialize an
atomic variable, before it can be accessed with the actual atomic ops.
Trying to use pg_atomic_write_u64 on an uninitialized variable leads to a
failure with the fallback implementation that uses a spinlock.
Discussion: https://www.postgresql.org/message-id/20170816191346.d3ke5tpshhco4bnd%40alap3.anarazel.de
Since commit 40dae7ec53, which changed the way b-tree page splitting
works, there has been no difference in the handling of root, and non-root
split WAL records. We don't need to distinguish them anymore
If you're worried about the loss of debugging information, note that
usually a root split record will normally be followed by a WAL record to
create the new root page. The root page will also have the BTP_ROOT flag
set on the page itself, and there is a pointer to it from the metapage.
Author: Aleksander Alekseev
Discussion: https://www.postgresql.org/message-id/20170406122116.GA11081@e733.localdomain
Stress testing by Andreas Seltenreich disclosed longstanding problems that
occur if a FATAL exit (e.g. due to receipt of SIGTERM) occurs while we are
trying to execute a ROLLBACK of an already-failed transaction. In such a
case, xact.c is in TBLOCK_ABORT state, so that AbortOutOfAnyTransaction
would skip AbortTransaction and go straight to CleanupTransaction. This
led to an assert failure in an assert-enabled build (due to the ROLLBACK's
portal still having a cleanup hook) or without assertions, to a FATAL exit
complaining about "cannot drop active portal". The latter's not
disastrous, perhaps, but it's messy enough to want to improve it.
We don't really want to run all of AbortTransaction in this code path.
The minimum required to clean up the open portal safely is to do
AtAbort_Memory and AtAbort_Portals. It seems like a good idea to
do AtAbort_Memory unconditionally, to be entirely sure that we are
starting with a safe CurrentMemoryContext. That means that if the
main loop in AbortOutOfAnyTransaction does nothing, we need an extra
step at the bottom to restore CurrentMemoryContext = TopMemoryContext,
which I chose to do by invoking AtCleanup_Memory. This'll result in
calling AtCleanup_Memory twice in many of the paths through this function,
but that seems harmless and reasonably inexpensive.
The original motivation for the assertion in AtCleanup_Portals was that
we wanted to be sure that any user-defined code executed as a consequence
of the cleanup hook runs during AbortTransaction not CleanupTransaction.
That still seems like a valid concern, and now that we've seen one case
of the assertion firing --- which means that exactly that would have
happened in a production build --- let's replace the Assert with a runtime
check. If we see the cleanup hook still set, we'll emit a WARNING and
just drop the hook unexecuted.
This has been like this a long time, so back-patch to all supported
branches.
Discussion: https://postgr.es/m/877ey7bmun.fsf@ansel.ydns.eu
The sole useful effect of this function, to check that no catcache
entries have positive refcounts at transaction end, has really been
obsolete since we introduced ResourceOwners in PG 8.1. We reduced the
checks to assertions years ago, so that the function was a complete
no-op in production builds. There have been previous discussions about
removing it entirely, but consensus up to now was that it had some small
value as a cross-check for bugs in the ResourceOwner logic.
However, it now emerges that it's possible to trigger these assertions
if you hit an assert-enabled backend with SIGTERM during a call to
SearchCatCacheList, because that function temporarily increases the
refcounts of entries it's intending to add to a catcache list construct.
In a normal ERROR scenario, the extra refcounts are cleaned up by
SearchCatCacheList's PG_CATCH block; but in a FATAL exit we do a
transaction abort and exit without ever executing PG_CATCH handlers.
There's a case to be made that this is a generic hazard and we should
consider restructuring elog(FATAL) handling so that pending PG_CATCH
handlers do get run. That's pretty scary though: it could easily create
more problems than it solves. Preliminary stress testing by Andreas
Seltenreich suggests that there are not many live problems of this ilk,
so we rejected that idea.
There are more-localized ways to fix the problem; the most principled
one would be to use PG_ENSURE_ERROR_CLEANUP instead of plain PG_TRY.
But adding cycles to SearchCatCacheList isn't very appealing. We could
also weaken the assertions in AtEOXact_CatCache in some more or less
ad-hoc way, but that just makes its raison d'etre even less compelling.
In the end, the most reasonable solution seems to be to just remove
AtEOXact_CatCache altogether, on the grounds that it's not worth trying
to fix it. It hasn't found any bugs for us in many years.
Per report from Jeevan Chalke. Back-patch to all supported branches.
Discussion: https://postgr.es/m/CAM2+6=VEE30YtRQCZX7_sCFsEpoUkFBV1gZazL70fqLn8rcvBA@mail.gmail.com
We must advance the oldest XID that can be safely looked up in clog
*before* truncating CLOG, and the oldest XID that can't be reused
*after* truncating CLOG. This assertion, and the accompanying
comment, are confused; remove them.
Reported by Neha Sharma.
Discussion: http://postgr.es/m/CANiYTQumC3T=UMBMd1Hor=5XWZYuCEQBioL3ug0YtNQCMMT5wQ@mail.gmail.com
Previously, it had no effect. Now, if archive_mode=always, it will
work, and if not, you'll get a warning.
Masahiko Sawada, Michael Paquier, and Robert Haas. The patch as
submitted also changed the behavior so that we would write and remove
history files on standbys, but that seems like material for a separate
patch to me.
Discussion: http://postgr.es/m/CAD21AoC2Xw6M=ZJyejq_9d_iDkReC_=rpvQRw5QsyzKQdfYpkw@mail.gmail.com
If it works, then we won't be storing two copies of all the tuples
that were just moved. If not, VACUUM will still take care of it
eventually. Per a report from AP and analysis from Amit Kapila, it
seems that a bulk load can cause splits fast enough that VACUUM won't
deal with the problem in time to prevent bloat.
Amit Kapila; I rewrote the comment.
Discussion: http://postgr.es/m/20170704105728.mwb72jebfmok2nm2@zip.com.au
If several sessions are concurrently locking a tuple update chain with
nonconflicting lock modes using an old snapshot, and they all succeed,
it may happen that some of them fail because of restarting the loop (due
to a concurrent Xmax change) and getting an error in the subsequent pass
while trying to obtain a tuple lock that they already have in some tuple
version.
This can only happen with very high concurrency (where a row is being
both updated and FK-checked by multiple transactions concurrently), but
it's been observed in the field and can have unpleasant consequences
such as an FK check failing to see a tuple that definitely exists:
ERROR: insert or update on table "child_table" violates foreign key constraint "fk_constraint_name"
DETAIL: Key (keyid)=(123456) is not present in table "parent_table".
(where the key is observably present in the table).
Discussion: https://postgr.es/m/20170714210011.r25mrff4nxjhmf3g@alvherre.pgsql
SLRU buffer lwlocks are allocated twice by oversight in commit
fe702a7b3f where that locks were moved to
separate tranche. The bug doesn't have user-visible effects except small
overspending of shared memory.
Backpatch to 9.6 where it was introduced.
Alexander Korotkov with small editorization by me.
When pg_control was first designed, sizeof(ControlFileData) was small
enough that a comment seemed like plenty to document the assumption that
it'd fit into one disk sector. Now it's nearly 300 bytes, raising the
possibility that somebody would carelessly add enough stuff to create
a problem. Let's add a StaticAssertStmt() to ensure that the situation
doesn't pass unnoticed if it ever occurs.
While at it, rename PG_CONTROL_SIZE to PG_CONTROL_FILE_SIZE to make it
clearer what that symbol means, and convert the existing runtime
comparisons of sizeof(ControlFileData) vs. PG_CONTROL_FILE_SIZE to be
static asserts --- we didn't have that technology when this code was
first written.
Discussion: https://postgr.es/m/9192.1500490591@sss.pgh.pa.us
One, logging for CREATE INDEX was oblivious to the fact that when
an unlogged table is created, *only* operations on the init fork
should be logged.
Two, init fork buffers need to be flushed after they are written;
otherwise, a filesystem-level copy following recovery may do the
wrong thing. (There may be a better fix for this issue than the
one used here, but this is transposed from the similar logic already
present in XLogReadBufferForRedoExtended, and a broader refactoring
after beta2 seems inadvisable.)
Amit Kapila, reviewed by Ashutosh Sharma, Kyotaro Horiguchi,
and Michael Paquier
Discussion: http://postgr.es/m/CAA4eK1JpcMsEtOL_J7WODumeEfyrPi7FPYHeVdS7fyyrCrgp4w@mail.gmail.com
When promoting a standby just after a XLOG_SWITCH record was replayed,
and next segment(s) are already are locally available (via walsender,
restore_command + trigger/recovery target), that segment could
accidentally be recycled onto the past of the new timeline. Later
checkpointer would create a .ready file for it, assuming there was an
error during creation, and it would get archived. That causes trouble
if another standby is later brought up from a basebackup from before
the timeline creation, because it would try to read the
segment, because XLogFileReadAnyTLI just tries all possible timelines,
which doesn't have valid contents. Thus replay would fail.
The problem, if already occurred, can be fixed by removing the segment
and/or having restore_command filter it out.
The reason for the creation of such "phantom" segments was, that after
an XLOG_SWITCH record the EndOfLog variable points to the beginning of
the next segment, and RemoveXlogFile() used XLByteToPrevSeg().
Normally RemoveXlogFile() doing so is harmless, because the last
segment will still exist preventing InstallXLogFileSegment() from
causing harm, but just after promotion there's no previous segment on
the new timeline.
Fix that by using XLByteToSeg() instead of XLByteToPrevSeg().
Author: Andres Freund
Reported-By: Greg Burek
Discussion: https://postgr.es/m/20170619073026.zcwpe6mydsaz5ygd@alap3.anarazel.de
Backpatch: 9.2-, bug older than all supported versions
Don't move parenthesized lines to the left, even if that means they
flow past the right margin.
By default, BSD indent lines up statement continuation lines that are
within parentheses so that they start just to the right of the preceding
left parenthesis. However, traditionally, if that resulted in the
continuation line extending to the right of the desired right margin,
then indent would push it left just far enough to not overrun the margin,
if it could do so without making the continuation line start to the left of
the current statement indent. That makes for a weird mix of indentations
unless one has been completely rigid about never violating the 80-column
limit.
This behavior has been pretty universally panned by Postgres developers.
Hence, disable it with indent's new -lpl switch, so that parenthesized
lines are always lined up with the preceding left paren.
This patch is much less interesting than the first round of indent
changes, but also bulkier, so I thought it best to separate the effects.
Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org
Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
Change pg_bsd_indent to follow upstream rules for placement of comments
to the right of code, and remove pgindent hack that caused comments
following #endif to not obey the general rule.
Commit e3860ffa4d wasn't actually using
the published version of pg_bsd_indent, but a hacked-up version that
tried to minimize the amount of movement of comments to the right of
code. The situation of interest is where such a comment has to be
moved to the right of its default placement at column 33 because there's
code there. BSD indent has always moved right in units of tab stops
in such cases --- but in the previous incarnation, indent was working
in 8-space tab stops, while now it knows we use 4-space tabs. So the
net result is that in about half the cases, such comments are placed
one tab stop left of before. This is better all around: it leaves
more room on the line for comment text, and it means that in such
cases the comment uniformly starts at the next 4-space tab stop after
the code, rather than sometimes one and sometimes two tabs after.
Also, ensure that comments following #endif are indented the same
as comments following other preprocessor commands such as #else.
That inconsistency turns out to have been self-inflicted damage
from a poorly-thought-through post-indent "fixup" in pgindent.
This patch is much less interesting than the first round of indent
changes, but also bulkier, so I thought it best to separate the effects.
Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org
Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
The new indent version includes numerous fixes thanks to Piotr Stefaniak.
The main changes visible in this commit are:
* Nicer formatting of function-pointer declarations.
* No longer unexpectedly removes spaces in expressions using casts,
sizeof, or offsetof.
* No longer wants to add a space in "struct structname *varname", as
well as some similar cases for const- or volatile-qualified pointers.
* Declarations using PG_USED_FOR_ASSERTS_ONLY are formatted more nicely.
* Fixes bug where comments following declarations were sometimes placed
with no space separating them from the code.
* Fixes some odd decisions for comments following case labels.
* Fixes some cases where comments following code were indented to less
than the expected column 33.
On the less good side, it now tends to put more whitespace around typedef
names that are not listed in typedefs.list. This might encourage us to
put more effort into typedef name collection; it's not really a bug in
indent itself.
There are more changes coming after this round, having to do with comment
indentation and alignment of lines appearing within parentheses. I wanted
to limit the size of the diffs to something that could be reviewed without
one's eyes completely glazing over, so it seemed better to split up the
changes as much as practical.
Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org
Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
The optimized code in 728bd991c3 contains a few invalid locking
sequences. To wit, the original code would try to acquire an lwlock
that it already holds. Avoid this by moving lock acquisitions to
higher-level code, and install appropriate assertions in low-level that
the correct mode is held.
Authors: Michael Paquier, Álvaro Herrera
Reported-By: chuanting wang
Bug: #14680
Discussion: https://postgr.es/m/20170531033228.1487.10124@wrigleys.postgresql.org
The larger part of this patch replaces usages of MyProc->procLatch
with MyLatch. The latter works even early during backend startup,
where MyProc->procLatch doesn't yet. While the affected code
shouldn't run in cases where it's not initialized, it might get copied
into places where it might. Using MyLatch is simpler and a bit faster
to boot, so there's little point to stick with the previous coding.
While doing so I noticed some weaknesses around newly introduced uses
of latches that could lead to missed events, and an omitted
CHECK_FOR_INTERRUPTS() call in worker_spi.
As all the actual bugs are in v10 code, there doesn't seem to be
sufficient reason to backpatch this.
Author: Andres Freund
Discussion:
https://postgr.es/m/20170606195321.sjmenrfgl2nu6j63@alap3.anarazel.dehttps://postgr.es/m/20170606210405.sim3yl6vpudhmufo@alap3.anarazel.de
Backpatch: -
When the checkpointer writes the shutdown checkpoint, it checks
afterwards whether any WAL has been written since it started and
throws a PANIC if so. At that point, only walsenders are still
active, so one might think this could not happen, but walsenders can
also generate WAL, for instance in BASE_BACKUP and logical decoding
related commands (e.g. via hint bits). So they can trigger this panic
if such a command is run while the shutdown checkpoint is being
written.
To fix this, divide the walsender shutdown into two phases. First,
checkpointer, itself triggered by postmaster, sends a
PROCSIG_WALSND_INIT_STOPPING signal to all walsenders. If the backend
is idle or runs an SQL query this causes the backend to shutdown, if
logical replication is in progress all existing WAL records are
processed followed by a shutdown. Otherwise this causes the walsender
to switch to the "stopping" state. In this state, the walsender will
reject any further replication commands. The checkpointer begins the
shutdown checkpoint once all walsenders are confirmed as
stopping. When the shutdown checkpoint finishes, the postmaster sends
us SIGUSR2. This instructs walsender to send any outstanding WAL,
including the shutdown checkpoint record, wait for it to be replicated
to the standby, and then exit.
Author: Andres Freund, based on an earlier patch by Michael Paquier
Reported-By: Fujii Masao, Andres Freund
Reviewed-By: Michael Paquier
Discussion: https://postgr.es/m/20170602002912.tqlwn4gymzlxpvs2@alap3.anarazel.de
Backpatch: 9.4, where logical decoding was introduced
This reverts commit 086221cf6b, which
was made to master only.
The approach implemented in the above commit has some issues. While
those could easily be fixed incrementally, doing so would make
backpatching considerably harder, so instead first revert this patch.
Discussion: https://postgr.es/m/20170602002912.tqlwn4gymzlxpvs2@alap3.anarazel.de
Given the possibility of race conditions and so on, it seems entirely
unsafe to just assume that shm_toc_lookup() always finds the key it's
looking for --- but that was exactly what all but one call site were
doing. To fix, add a "bool noError" argument, similarly to what we
have in many other functions, and throw an error on an unexpected
lookup failure. Remove now-redundant Asserts that a rather random
subset of call sites had.
I doubt this will throw any light on buildfarm member lorikeet's
recent failures, because if an unnoticed lookup failure were involved,
you'd kind of expect a null-pointer-dereference crash rather than the
observed symptom. But you never know ... and this is better coding
practice even if it never catches anything.
Discussion: https://postgr.es/m/9697.1496675981@sss.pgh.pa.us
Remove some gratuituous message differences by making the AM name
previously embedded in each message be a %s instead. While at it, get
rid of terminology that's unclear and unnecessary in one message.
Discussion: https://postgr.es/m/20170523001557.bq2hbq7hxyvyw62q@alvherre.pgsql
Per discussion, "location" is a rather vague term that could refer to
multiple concepts. "LSN" is an unambiguous term for WAL locations and
should be preferred. Some function names, view column names, and function
output argument names used "lsn" already, but others used "location",
as well as yet other terms such as "wal_position". Since we've already
renamed a lot of things in this area from "xlog" to "wal" for v10,
we may as well incur a bit more compatibility pain and make these names
all consistent.
David Rowley, minor additional docs hacking by me
Discussion: https://postgr.es/m/CAKJS1f8O0njDKe8ePFQ-LK5-EjwThsDws6ohJ-+c6nWK+oUxtg@mail.gmail.com
This reverts commits fa2fa99552 and 42f50cb8fa.
While the functionality that was intended to be provided by these
commits is desired, the patch didn't actually solve as many of the
problematic situations as we hoped, and it created a bunch of its own
problems. Since we're going to require more extensive changes soon for
other reasons and users have been working around these problems for a
long time already, there is no point in spending effort in fixing this
halfway measure.
Per complaint from Tom Lane.
Discussion: https://postgr.es/m/21407.1484606922@sss.pgh.pa.us
(Commit fa2fa99552 had already been reverted in branches 9.5 as
f858524ee4 and 9.6 as e9e44a0953, so this touches master only.
Commit 42f50cb8fa was not present in the older branches.)
When the checkpointer writes the shutdown checkpoint, it checks
afterwards whether any WAL has been written since it started and throws
a PANIC if so. At that point, only walsenders are still active, so one
might think this could not happen, but walsenders can also generate WAL,
for instance in BASE_BACKUP and certain variants of
CREATE_REPLICATION_SLOT. So they can trigger this panic if such a
command is run while the shutdown checkpoint is being written.
To fix this, divide the walsender shutdown into two phases. First, the
postmaster sends a SIGUSR2 signal to all walsenders. The walsenders
then put themselves into the "stopping" state. In this state, they
reject any new commands. (For simplicity, we reject all new commands,
so that in the future we do not have to track meticulously which
commands might generate WAL.) The checkpointer waits for all walsenders
to reach this state before proceeding with the shutdown checkpoint.
After the shutdown checkpoint is done, the postmaster sends
SIGINT (previously unused) to the walsenders. This triggers the
existing shutdown behavior of sending out the shutdown checkpoint record
and then terminating.
Author: Michael Paquier <michael.paquier@gmail.com>
Reported-by: Fujii Masao <masao.fujii@gmail.com>
GiST's getNextNearest() function attempts to pfree the previously-returned
tuple if any (that is, scan->xs_hitup in HEAD, or scan->xs_itup in older
branches). However, if we are rescanning a plan node after ending a
previous scan early, those tuple pointers could be pointing to garbage,
because they would be pointing into the scan's pageDataCxt or queueCxt
which has been reset. In a debug build this reliably results in a crash,
although I think it might sometimes accidentally fail to fail in
production builds.
To fix, clear the pointer field anyplace we reset a context it might
be pointing into. This may be overkill --- I think probably only the
queueCxt case is involved in this bug, so that resetting in gistrescan()
would be sufficient --- but dangling pointers are generally bad news,
so let's avoid them.
Another plausible answer might be to just not bother with the pfree in
getNextNearest(). The reconstructed tuples would go away anyway in the
context resets, and I'm far from convinced that freeing them a bit earlier
really saves anything meaningful. I'll stick with the original logic in
this patch, but if we find more problems in the same area we should
consider that approach.
Per bug #14641 from Denis Smirnov. Back-patch to 9.5 where this
logic was introduced.
Discussion: https://postgr.es/m/20170504072034.24366.57688@wrigleys.postgresql.org
After the logical replication launcher was told to wake up at
commit (for example, by a CREATE SUBSCRIPTION command), the flag to wake
up was not reset, so it would be woken up at every following commit as
well. So fix that by resetting the flag.
Also, we don't need to wake up anything if the transaction was rolled
back. Just reset the flag in that case.
Author: Masahiko Sawada <sawada.mshk@gmail.com>
Reported-by: Fujii Masao <masao.fujii@gmail.com>
ProcessTwoPhaseBuffer (formerly StandbyRecoverPreparedTransactions)
mixed up the parent and child XIDs when calling SubTransSetParent to
record the transactions' relationship in pg_subtrans.
Remarkably, analysis by Simon Riggs suggests that this doesn't lead to
visible problems (at least, not in non-Assert builds). That might
explain why we'd not noticed it before. Nonetheless, it's surely wrong.
This code was born broken, so back-patch to all supported branches.
Discussion: https://postgr.es/m/20110.1492905318@sss.pgh.pa.us
Doing so allows various crash possibilities. Fix by avoiding
having PrescanPreparedTransactions() increment
ShmemVariableCache->nextXid when it has no 2PC files
Bug found by Jeff Janes, diagnosis and patch by Pavan Deolasee,
then patch re-designed for clarity and full accuracy by
Michael Paquier.
Reported-by: Jeff Janes
Author: Pavan Deolasee, Michael Paquier
Discussion: https://postgr.es/m/CAMkU=1zMLnH_i1-PVQ-biZzvNx7VcuatriquEnh7HNk6K8Ss3Q@mail.gmail.com
Coverity complained because bgw.bgw_extra wasn't being filled in by
ApplyLauncherRegister(). The most future-proof fix is to memset the
whole BackgroundWorker struct to zeroes. While at it, let's apply the
same coding rule to other places that set up BackgroundWorker structs;
four out of five had the same or related issues.
We'd already recognized that we can't pass function pointers across process
boundaries for functions in loadable modules, since a shared library could
get loaded at different addresses in different processes. But actually the
practice doesn't work for functions in the core backend either, if we're
using EXEC_BACKEND. This is the cause of recent failures on buildfarm
member culicidae. Switch to passing a string function name in all cases.
Something like this needs to be back-patched into 9.6, but let's see
if the buildfarm likes it first.
Petr Jelinek, with a bunch of basically-cosmetic adjustments by me
Discussion: https://postgr.es/m/548f9c1d-eafa-e3fa-9da8-f0cc2f654e60@2ndquadrant.com
Standardize on testing a hash index page's type by doing
(opaque->hasho_flag & LH_PAGE_TYPE) == LH_xxx_PAGE
Various places were taking shortcuts like
opaque->hasho_flag & LH_BUCKET_PAGE
which while not actually wrong, is still bad practice because
it encourages use of
opaque->hasho_flag & LH_UNUSED_PAGE
which *is* wrong (LH_UNUSED_PAGE == 0, so the above is constant false).
hash_xlog.c's hash_mask() contained such an incorrect test.
This also ensures that we mask out the additional flag bits that
hasho_flag has accreted since 9.6. pgstattuple's pgstat_hash_page(),
for one, was failing to do that and was thus actively broken.
Also fix assorted comments that hadn't been updated to reflect the
extended usage of hasho_flag, and fix some macros that were testing
just "(hasho_flag & bit)" to use the less dangerous, project-approved
form "((hasho_flag & bit) != 0)".
Coverity found the bug in hash_mask(); I noted the one in
pgstat_hash_page() through code reading.
Instead of allocating memory in brin_deform_tuple and brin_copy_tuple
over and over during a scan, allow reuse of previously allocated memory.
This is said to make for a measurable performance improvement.
Author: Jinyu Zhang, Álvaro Herrera
Reviewed by: Tomas Vondra
Discussion: https://postgr.es/m/495deb78.4186.1500dacaa63.Coremail.beijing_pg@163.com
The WAL-writing piece was forgetting to set the pages-per-range value.
Also, fix the declared type of struct member heapBlk, which I mistakenly
set as OffsetNumber rather than BlockNumber.
Problem was introduced by commit c655899ba9 (April 1st). Any system
that tries to replay the new WAL record written before this fix is
likely to die on replay and require pg_resetwal.
Reported by Tom Lane.
Discussion: https://postgr.es/m/20191.1491524824@sss.pgh.pa.us
tupconvert.c's functions formerly considered that an explicit tuple
conversion was necessary if the input and output tupdescs contained
different type OIDs. The point of that was to make sure that a composite
datum resulting from the conversion would contain the destination rowtype
OID in its composite-datum header. However, commit 3838074f8 entirely
misunderstood what that check was for, thinking that it had something to do
with presence or absence of an OID column within the tuple. Removal of the
check broke the no-op conversion path in ExecEvalConvertRowtype, as
reported by Ashutosh Bapat.
It turns out that of the dozen or so call sites for tupconvert.c functions,
ExecEvalConvertRowtype is the only one that cares about the composite-datum
header fields in the output tuple. In all the rest, we'd much rather avoid
an unnecessary conversion whenever the tuples are physically compatible.
Moreover, the comments in tupconvert.c only promise physical compatibility
not a metadata match. So, let's accept the removal of the guarantee about
the output tuple's rowtype marking, recognizing that this is a API change
that could conceivably break third-party callers of tupconvert.c. (So,
let's remember to mention it in the v10 release notes.)
However, commit 3838074f8 did have a bit of a point here, in that two
tuples mustn't be considered physically compatible if one has HEAP_HASOID
set and the other doesn't. (Some of the callers of tupconvert.c might not
really care about that, but we can't assume it in general.) The previous
check accidentally covered that issue, because no RECORD types ever have
OIDs, while if two tupdescs have the same named composite type OID then,
a fortiori, they have the same tdhasoid setting. If we're removing the
type OID match check then we'd better include tdhasoid match as part of
the physical compatibility check.
Without that hack in tupconvert.c, we need ExecEvalConvertRowtype to take
responsibility for inserting the correct rowtype OID label whenever
tupconvert.c decides it need not do anything. This is easily done with
heap_copy_tuple_as_datum, which will be considerably faster than a tuple
disassembly and reassembly anyway; so from a performance standpoint this
change is a win all around compared to what happened in earlier branches.
It just means a couple more lines of code in ExecEvalConvertRowtype.
Ashutosh Bapat and Tom Lane
Discussion: https://postgr.es/m/CAFjFpRfvHABV6+oVvGcshF8rHn+1LfRUhj7Jz1CDZ4gPUwehBg@mail.gmail.com
The original code was overly optimistic about the cost of scanning a
BRIN index, leading to BRIN indexes being selected when they'd be a
worse choice than some other index. This complete rewrite should be
more accurate.
Author: David Rowley, based on an earlier patch by Emre Hasegeli
Reviewed-by: Emre Hasegeli
Discussion: https://postgr.es/m/CAKJS1f9n-Wapop5Xz1dtGdpdqmzeGqQK4sV2MK-zZugfC14Xtw@mail.gmail.com
This is the SQL standard-conforming variant of PostgreSQL's serial
columns. It fixes a few usability issues that serial columns have:
- CREATE TABLE / LIKE copies default but refers to same sequence
- cannot add/drop serialness with ALTER TABLE
- dropping default does not drop sequence
- need to grant separate privileges to sequence
- other slight weirdnesses because serial is some kind of special macro
Reviewed-by: Vitaly Burovoy <vitaly.burovoy@gmail.com>
For normal commits and aborts we already reset PgXact->xmin,
so we can simply avoid running SnapshotResetXmin() twice.
During performance tests by Alexander Korotkov, diagnosis
by Andres Freund showed PgXact array as a bottleneck. After
manual analysis by me of the code paths that touch those
memory locations, I was able to identify extraneous code
in the main transaction commit path.
Avoiding touching highly contented shmem improves concurrent
performance slightly on all workloads, confirmed by tests
run by Ashutosh Sharma and Alexander Korotkov.
Simon Riggs
Discussion: CANP8+jJdXE9b+b9F8CQT-LuxxO0PBCB-SZFfMVAdp+akqo4zfg@mail.gmail.com
Make every page in a hash index which isn't all-zeroes have a valid
special space, so that tools like pageinspect don't error out.
Also, make pageinspect cope with all-zeroes pages, because
_hash_alloc_buckets can leave behind large numbers of those until
they're consumed by splits.
Ashutosh Sharma and Robert Haas, reviewed by Amit Kapila.
Original trouble report from Jeff Janes.
Discussion: http://postgr.es/m/CAMkU=1y6NjKmqbJ8wLMhr=F74WzcMALYWcVFhEpm7i=mV=XsOg@mail.gmail.com
Previously they were defined using multiples of XLogSegSize.
Remove GUC_UNIT_XSEGS. Introduce GUC_UNIT_MB
Extracted from patch series on XLogSegSize infrastructure.
Beena Emerson
2PC state info held in shmem at PREPARE, then cleaned at COMMIT PREPARED/ABORT PREPARED,
avoiding writing/fsyncing any state information to disk in the normal path, greatly enhancing replay speed.
Prepared transactions that live past one checkpoint redo horizon will be written to disk as now.
Similar conceptually to 978b2f65aa and building upon
the infrastructure created by that commit.
Authors, in equal measure: Stas Kelvich, Nikhil Sontakke and Michael Paquier
Discussion: https://postgr.es/m/CAMGcDxf8Bn9ZPBBJZba9wiyQq-Qk5uqq=VjoMnRnW5s+fKST3w@mail.gmail.com
Since hash indexes typically have very few overflow pages, adding a
new splitpoint essentially doubles the on-disk size of the index,
which can lead to large and abrupt increases in disk usage (and
perhaps long delays on occasion). To mitigate this problem to some
degree, divide larger splitpoints into four equal phases. This means
that, for example, instead of growing from 4GB to 8GB all at once, a
hash index will now grow from 4GB to 5GB to 6GB to 7GB to 8GB, which
is perhaps still not as smooth as we'd like but certainly an
improvement.
This changes the on-disk format of the metapage, so bump HASH_VERSION
from 2 to 3. This will force a REINDEX of all existing hash indexes,
but that's probably a good idea anyway. First, hash indexes from
pre-10 versions of PostgreSQL could easily be corrupted, and we don't
want to confuse corruption carried over from an older release with any
corruption caused despite the new write-ahead logging in v10. Second,
it will let us remove some backward-compatibility code added by commit
293e24e507.
Mithun Cy, reviewed by Amit Kapila, Jesper Pedersen and me. Regression
test outputs updated by me.
Discussion: http://postgr.es/m/CAD__OuhG6F1gQLCgMQNnMNgoCvOLQZz9zKYJQNYvYmmJoM42gA@mail.gmail.com
Discussion: http://postgr.es/m/CA+TgmoYty0jCf-pa+m+vYUJ716+AxM7nv_syvyanyf5O-L_i2A@mail.gmail.com
In a couple of places, _hash_kill_items was mistakenly called with
the buffer lock not held. Repair.
Ashutosh Sharma, per a report from Andreas Seltenreich
Discussion: http://postgr.es/m/87o9wo8o0j.fsf@credativ.de
When the BRIN summary tuple for a page range becomes too "wide" for the
values actually stored in the table (because the tuples that were
present originally are no longer present due to updates or deletes), it
can be useful to remove the outdated summary tuple, so that a future
summarization can install a tighter summary.
This commit introduces a SQL-callable interface to do so.
Author: Álvaro Herrera
Reviewed-by: Eiji Seki
Discussion: https://postgr.es/m/20170228045643.n2ri74ara4fhhfxf@alvherre.pgsql
Previously, only VACUUM would cause a page range to get initially
summarized by BRIN indexes, which for some use cases takes too much time
since the inserts occur. To avoid the delay, have brininsert request a
summarization run for the previous range as soon as the first tuple is
inserted into the first page of the next range. Autovacuum is in charge
of processing these requests, after doing all the regular vacuuming/
analyzing work on tables.
This doesn't impose any new tasks on autovacuum, because autovacuum was
already in charge of doing summarizations. The only actual effect is to
change the timing, i.e. that it occurs earlier. For this reason, we
don't go any great lengths to record these requests very robustly; if
they are lost because of a server crash or restart, they will happen at
a later time anyway.
Most of the new code here is in autovacuum, which can now be told about
"work items" to process. This can be used for other things such as GIN
pending list cleaning, perhaps visibility map bit setting, both of which
are currently invoked during vacuum, but do not really depend on vacuum
taking place.
The requests are at the page range level, a granularity for which we did
not have SQL-level access; we only had index-level summarization
requests via brin_summarize_new_values(). It seems reasonable to add
SQL-level access to range-level summarization too, so add a function
brin_summarize_range() to do that.
Authors: Álvaro Herrera, based on sketch from Simon Riggs.
Reviewed-by: Thomas Munro.
Discussion: https://postgr.es/m/20170301045823.vneqdqkmsd4as4ds@alvherre.pgsql
On EXEC_BACKEND builds, this can fail if ASLR is in use.
Backpatch to 9.5. On master, completely remove the bgw_main field
completely, since there is no situation in which it is safe for an
EXEC_BACKEND build. On 9.6 and 9.5, leave the field intact to avoid
breaking things for third-party code that doesn't care about working
under EXEC_BACKEND. Prior to 9.5, there are no in-core bgworker
entrypoints.
Petr Jelinek, reviewed by me.
Discussion: http://postgr.es/m/09d8ad33-4287-a09b-a77f-77f8761adb5e@2ndquadrant.com
Also, don't allow setting reloptions on them, since that would have no
effect given the lack of storage. The patch does this by introducing
a new reloption kind for which there are currently no reloptions -- we
might have some in the future -- so it adjusts parseRelOptions to
handle that case correctly.
Bumped catversion. System catalogs that contained reloptions for
partitioned tables are no longer valid; plus, there are now fewer
physical files on disk, which is not technically a catalog change but
still a good reason to re-initdb.
Amit Langote, reviewed by Maksim Milyutin and Kyotaro Horiguchi and
revised a bit by me.
Discussion: http://postgr.es/m/20170331.173326.212311140.horiguchi.kyotaro@lab.ntt.co.jp
The old coding was getting more complicated as new things were added,
and it would be barely tolerable with upcoming WARM updates and other
future features such as indirect indexes. The new coding incurs a small
performance cost in synthetic benchmark cases, and is barely measurable
in normal cases. A much larger benefit is expected from WARM, which
could actually bolt its needs on top of the existing coding, but it is
much uglier and bug-prone than doing it on this new code. Additional
optimization can be applied on top of this, if need be.
Reviewed-by: Pavan Deolasee, Amit Kapila, Mithun CY
Discussion: https://postgr.es/m/20161228232018.4hc66ndrzpz4g4wn@alvherre.pgsqlhttps://postgr.es/m/CABOikdMJfz69dBNRTOZcB6s5A0tf8OMCyQVYQyR-WFFdoEwKMQ@mail.gmail.com
There are no functional changes here; this simply encapsulates knowledge
of the ItemPointerData struct so that a future patch can change things
without more breakage.
All direct users of ip_blkid and ip_posid are changed to use existing
macros ItemPointerGetBlockNumber and ItemPointerGetOffsetNumber
respectively. For callers where that's inappropriate (because they
Assert that the itempointer is is valid-looking), add
ItemPointerGetBlockNumberNoCheck and ItemPointerGetOffsetNumberNoCheck,
which lack the assertion but are otherwise identical.
Author: Pavan Deolasee
Discussion: https://postgr.es/m/CABOikdNnFon4cJiL=h1mZH3bgUeU+sWHuU4Yr8AB=j3A2p1GiA@mail.gmail.com
We were assigning values near 255 through "char *" pointers. On machines
where char is signed, that's not entirely kosher, and it's reasonable
for compilers to warn about it.
A better solution would be to change the pointer type to "unsigned char *",
but that would be vastly more invasive. For the moment, let's just apply
this simple backpatchable solution.
Aleksander Alekseev
Discussion: https://postgr.es/m/20170220141239.GD12278@e733.localdomain
Discussion: https://postgr.es/m/2839.1490714708@sss.pgh.pa.us
Most seriously, fix use of incorrect block ID, per a report from
Jeff Janes that it causes a crash and a diagnosis from Amit Kapila.
Improve consistency between the hash and btree versions of this
code by adding back a PANIC that btree has, and by registering
data in the xlog record in the same way, per complaints from
Jeff Janes and Amit Kapila.
Tidy up some minor cosmetic points, per complaints from Amit
Kapila.
Patch by Ashutosh Sharma, reviewed by Amit Kapila, and tested by
Jeff Janes.
Discussion: http://postgr.es/m/CAMkU=1w-9Qe=Ff1o6bSaXpNO9wqpo7_9GL8_CVhw4BoVVHasqg@mail.gmail.com
If file was created/deleted just before powerloss it's possible that
file system will miss that. To prevent it, call fsync() where creating/
unlinkg file is critical.
Author: Michael Paquier
Reviewed-by: Ashutosh Bapat, Takayuki Tsunakawa, me
In commit b8d7f053c, we needed to fix ExecEvalWholeRowVar to not change
the state of the slot it's copying. The initial quick hack at that
required two rounds of tuple construction, which is not very nice.
To fix, add another primitive to tuptoaster.c that does precisely what
we need. (I initially tried to do this by refactoring one of the
existing functions into two pieces; but it looked like that might hurt
performance for the existing case, and the amount of code that could
be shared is not very large, so I gave up on that.)
Discussion: https://postgr.es/m/26088.1490315792@sss.pgh.pa.us
Assert-enabled build crashes but without asserts it works by wrong way:
it may not reset forcing full page write and preventing from starting
exclusive backup with the same name as cancelled.
Patch replaces pair of booleans
nonexclusive_backup_running/exclusive_backup_running to single enum to
correctly describe backup state.
Backpatch to 9.6 where bug was introduced
Reported-by: David Steele
Authors: Michael Paquier, David Steele
Reviewed-by: Anastasia Lubennikova
https://commitfest.postgresql.org/13/1068/
This provides infrastructure for looking up arbitrary, user-supplied
XIDs without a risk of scary-looking failures from within the clog
module. Normally, the oldest XID that can be safely looked up in CLOG
is the same as the oldest XID that can reused without causing
wraparound, and the latter is already tracked. However, while
truncation is in progress, the values are different, so we must
keep track of them separately.
Craig Ringer, reviewed by Simon Riggs and by me.
Discussion: http://postgr.es/m/CAMsr+YHQiWNEi0daCTboS40T+V5s_+dst3PYv_8v2wNVH+Xx4g@mail.gmail.com
GIN vacuum during cleaning posting tree can lock this whole tree for a long
time with by holding LockBufferForCleanup() on root. Patch changes it with
two ways: first, cleanup lock will be taken only if there is an empty page
(which should be deleted) and, second, it tries to lock only subtree, not the
whole posting tree.
Author: Andrey Borodin with minor editorization by me
Reviewed-by: Jeff Davis, me
https://commitfest.postgresql.org/13/896/
Adds write_lag, flush_lag and replay_lag cols to pg_stat_replication.
Implements a lag tracker module that reports the lag times based upon
measurements of the time taken for recent WAL to be written, flushed and
replayed and for the sender to hear about it. These times
represent the commit lag that was (or would have been) introduced by each
synchronous commit level, if the remote server was configured as a
synchronous standby. For an asynchronous standby, the replay_lag column
approximates the delay before recent transactions became visible to queries.
If the standby server has entirely caught up with the sending server and
there is no more WAL activity, the most recently measured lag times will
continue to be displayed for a short time and then show NULL.
Physical replication lag tracking is automatic. Logical replication tracking
is possible but is the responsibility of the logical decoding plugin.
Tracking is a private module operating within each walsender individually,
with values reported to shared memory. Module not used outside of walsender.
Design and code is good enough now to commit - kudos to the author.
In many ways a difficult topic, with important and subtle behaviour so this
shoudl be expected to generate discussion and multiple open items: Test now!
Author: Thomas Munro, following designs by Fujii Masao and Simon Riggs
Review: Simon Riggs, Ian Barwick and Craig Ringer
Internally, we have supported the option to either wait for all of the
WAL associated with a backup to be archived, or to return immediately.
This option is useful to users of pg_stop_backup() as well, when they
are reading the stop backup record position and checking that the WAL
they need has been archived independently.
This patch adds an additional, optional, argument to pg_stop_backup()
which allows the user to indicate if they wish to wait for the WAL to be
archived or not. The default matches current behavior, which is to
wait.
Author: David Steele, with some minor changes, doc updates by me.
Reviewed by: Takayuki Tsunakawa, Fujii Masao
Discussion: https://postgr.es/m/758e3fd1-45b4-5e28-75cd-e9e7f93a4c02@pgmasters.net
A hot standby replica keeps a list of Access Exclusive locks for a top
level transaction. These locks are released when the top level transaction
ends. Searching of this list is O(N^2), and each transaction had to pay the
price of searching this list for locks, even if it didn't take any AE
locks itself.
This patch optimizes this case by having the master server track which
transactions took AE locks, and passes that along to the standby server in
the commit/abort record. This allows the standby to only try to release
locks for transactions which actually took any, avoiding the majority of
the performance issue.
Refactor MyXactAccessedTempRel into MyXactFlags to allow minimal additional
cruft with this.
Analysis and initial patch by David Rowley
Author: David Rowley and Simon Riggs
Uses page-based mechanism to ensure we’re using the correct timeline.
Tests are included to exercise the functionality using a cold disk-level copy
of the master that's started up as a replica with slots intact, but the
intended use of the functionality is with later features.
Craig Ringer, reviewed by Simon Riggs and Andres Freund
Clear LH_PAGE_HAS_DEAD_TUPLES during replay, similar to what gets done
for btree. Update hashdesc.c for xl_hash_vacuum_one_page.
Oversights in commit 6977b8b7f4 spotted
by Amit Kapila. Patch by Ashutosh Sharma.
Bump WAL version. The original patch to make hash indexes write-ahead
logged probably should have done this, and the single page vacuuming
patch probably should have done it again, but better late than never.
Discussion: http://postgr.es/m/CAA4eK1Kd=mJ9xreovcsh0qMiAj-QqCphHVQ_Lfau1DR9oVjASQ@mail.gmail.com
Previous commits, notably 53be0b1add and
6f3bd98ebf, made it possible to see from
pg_stat_activity when a backend was stuck waiting for another backend,
but it's also fairly common for a backend to be stuck waiting for an
I/O. Add wait events for those operations, too.
Rushabh Lathia, with further hacking by me. Reviewed and tested by
Michael Paquier, Amit Kapila, Rajkumar Raghuwanshi, and Rahila Syed.
Discussion: http://postgr.es/m/CAGPqQf0LsYHXREPAZqYGVkDqHSyjf=KsD=k0GTVPAuzyThh-VQ@mail.gmail.com
The warning about hash indexes not being write-ahead logged and their
use being discouraged has been removed. "snapshot too old" is now
supported for tables with hash indexes. Most importantly, barring
bugs, hash indexes will now be crash-safe and usable on standbys.
This commit doesn't yet add WAL consistency checking for hash
indexes, as we now have for other index types; a separate patch has
been submitted to cure that lack.
Amit Kapila, reviewed and slightly modified by me. The larger patch
series of which this is a part has been reviewed and tested by Álvaro
Herrera, Ashutosh Sharma, Mark Kirkwood, Jeff Janes, and Jesper
Pedersen.
Discussion: http://postgr.es/m/CAA4eK1JOBX=YU33631Qh-XivYXtPSALh514+jR8XeD7v+K3r_Q@mail.gmail.com
The original messaging design, introduced in commit 068cfadf9, seems too
chatty now that some time has elapsed since the bug fix; most installations
will be in good shape and don't really need a reminder about this on every
postmaster start.
Hence, arrange to suppress the "wraparound protections are now enabled"
message during startup (specifically, during the TrimMultiXact() call).
The message will still appear if protection becomes effective at some
later point.
Discussion: https://postgr.es/m/17211.1489189214@sss.pgh.pa.us
This makes almost all core code follow the policy introduced in the
previous commit. Specific decisions:
- Text search support functions with char* and length arguments, such as
prsstart and lexize, may receive unaligned strings. I doubt
maintainers of non-core text search code will notice.
- Use plain VARDATA() on values detoasted or synthesized earlier in the
same function. Use VARDATA_ANY() on varlenas sourced outside the
function, even if they happen to always have four-byte headers. As an
exception, retain the universal practice of using VARDATA() on return
values of SendFunctionCall().
- Retain PG_GETARG_BYTEA_P() in pageinspect. (Page images are too large
for a one-byte header, so this misses no optimization.) Sites that do
not call get_page_from_raw() typically need the four-byte alignment.
- For now, do not change btree_gist. Its use of four-byte headers in
memory is partly entangled with storage of 4-byte headers inside
GBT_VARKEY, on disk.
- For now, do not change gtrgm_consistent() or gtrgm_distance(). They
incorporate the varlena header into a cache, and there are multiple
credible implementation strategies to consider.
In functions that issue a deconstruct_array() call, consistently use
plain VARSIZE()/VARDATA() on the array elements. Prior practice was
divided between those and VARSIZE_ANY_EXHDR()/VARDATA_ANY().
This reverts commit ccce90b398. This
optimization is unsafe, at least, of rollbacks and rollbacks to
savepoints, but I'm concerned there may be other problematic cases as
well. Therefore, I've decided to revert this pending further
investigation.
Commit 0e141c0fbb introduced a mechanism
to reduce contention on ProcArrayLock by having a single process clear
XIDs in the procArray on behalf of multiple processes, reducing the
need to hand the lock around. Use a similar mechanism to reduce
contention on CLogControlLock. Testing shows that this very
significantly reduces the amount of time waiting for CLogControlLock
on high-concurrency pgbench tests run on a large multi-socket
machines; whether that translates into a TPS improvement depends on
how much of that contention is simply shifted to some other lock,
particularly WALWriteLock.
Amit Kapila, with some cosmetic changes by me. Extensively reviewed,
tested, and benchmarked over a period of about 15 months by Simon
Riggs, Robert Haas, Andres Freund, Jesper Pedersen, and especially by
Tomas Vondra and Dilip Kumar.
Discussion: http://postgr.es/m/CAA4eK1L_snxM_JcrzEstNq9P66++F4kKFce=1r5+D1vzPofdtg@mail.gmail.com
Discussion: http://postgr.es/m/CAA4eK1LyR2A+m=RBSZ6rcPEwJ=rVi1ADPSndXHZdjn56yqO6Vg@mail.gmail.com
Discussion: http://postgr.es/m/91d57161-d3ea-0cc2-6066-80713e4f90d7@2ndquadrant.com
Further fallout from commit c29aff959: there are some files that need
<float.h>, and were getting it from datatype/timestamp.h, but it was not
apparent in my (tgl's) testing because the requirement for <float.h>
exists only on certain Windows toolchains.
Report and patch by David Rowley.
Discussion: https://postgr.es/m/CAKJS1f-BHceaFzZScFapDV48gUVM2CAOBfhkgffdqXzFb+kwew@mail.gmail.com
The index is scanned by a single process, but then all cooperating
processes can iterate jointly over the resulting set of heap blocks.
In the future, we might also want to support using a parallel bitmap
index scan to set up for a parallel bitmap heap scan, but that's a
job for another day.
Dilip Kumar, with some corrections and cosmetic changes by me. The
larger patch set of which this is a part has been reviewed and tested
by (at least) Andres Freund, Amit Khandekar, Tushar Ahuja, Rafia
Sabih, Haribabu Kommi, Thomas Munro, and me.
Discussion: http://postgr.es/m/CAFiTN-uc4=0WxRGfCzs-xfkMYcSEWUC-Fon6thkJGjkh9i=13A@mail.gmail.com
Andres Freund
Tom Lane
Alvaro Herrera
Robert Haas
Peter Eisentraut
Simon Riggs
Heikki Linnakangas
Teodor Sigaev
Magnus Hagander
Bruce Momjian
Stephen Frost
Noah Misch