If the initial snapshot had overflowed then we can start whenever
the latest snapshot is empty, not overflowed or as we did already,
start when the xmin on primary was higher than xmax of our starting
snapshot, which proves we have full snapshot data.
Bug report by Chris Redekop
In assert-enabled builds, we assert during the shutdown sequence that
the queues have been properly emptied, and during process startup that
we are inheriting empty queues. In non-assert enabled builds, we just
save a few cycles.
This allows us to give correct syntax error pointers when complaining
about ungrouped variables in a join query with aggregates or GROUP BY.
It's pretty much irrelevant for the planner's use of the function, though
perhaps it might aid debugging sometimes.
If a tuple in a syscache contains an out-of-line toasted field, and we
try to fetch that field shortly after some other transaction has committed
an update or deletion of the tuple, there is a race condition: vacuum
could come along and remove the toast tuples before we can fetch them.
This leads to transient failures like "missing chunk number 0 for toast
value NNNNN in pg_toast_2619", as seen in recent reports from Andrew
Hammond and Tim Uckun.
The design idea of syscache is that access to stale syscache entries
should be prevented by relation-level locks, but that fails for at least
two cases where toasted fields are possible: ANALYZE updates pg_statistic
rows without locking out sessions that might want to plan queries on the
same table, and CREATE OR REPLACE FUNCTION updates pg_proc rows without
any meaningful lock at all.
The least risky fix seems to be an idea that Heikki suggested when we
were dealing with a related problem back in August: forcibly detoast any
out-of-line fields before putting a tuple into syscache in the first place.
This avoids the problem because at the time we fetch the parent tuple from
the catalog, we should be holding an MVCC snapshot that will prevent
removal of the toast tuples, even if the parent tuple is outdated
immediately after we fetch it. (Note: I'm not convinced that this
statement holds true at every instant where we could be fetching a syscache
entry at all, but it does appear to hold true at the times where we could
fetch an entry that could have a toasted field. We will need to be a bit
wary of adding toast tables to low-level catalogs that don't have them
already.) An additional benefit is that subsequent uses of the syscache
entry should be faster, since they won't have to detoast the field.
Back-patch to all supported versions. The problem is significantly harder
to reproduce in pre-9.0 releases, because of their willingness to flush
every entry in a syscache whenever the underlying catalog is vacuumed
(cf CatalogCacheFlushRelation); but there is still a window for trouble.
bgwriter is now a much less important process, responsible for page
cleaning duties only. checkpointer is now responsible for checkpoints
and so has a key role in shutdown. Later patches will correct doc
references to the now old idea that bgwriter performs checkpoints.
Has beneficial effect on performance at high write rates, but mainly
refactoring to more easily allow changes for power reduction by
simplifying previously tortuous code around required to allow page
cleaning and checkpointing to time slice in the same process.
Patch by me, Review by Dickson Guedes
The existing scan-direction-sensitive tests were overly complex, and
failed to stop the scan in cases where it's perfectly legitimate to do so.
Per bug #6278 from Maksym Boguk.
Back-patch to 8.3, which is as far back as the patch applies easily.
Doesn't seem worth sweating over a relatively minor performance issue in
8.2 at this late date. (But note that this was a performance regression
from 8.1 and before, so 8.2 is being left as an outlier.)
The POSIX spec defines locale fields for controlling the ordering of the
value, sign, and currency symbol in monetary output, but cash_out only
supported a small subset of these options. Fully implement p/n_sign_posn,
p/n_cs_precedes, and p/n_sep_by_space per spec. Fix up cash_in so that
it will accept all these format variants.
Also, make sure that thousands_sep is only inserted to the left of the
decimal point, as required by spec.
Per bug #6144 from Eduard Kracmar and discussion of bug #6277. This patch
includes some ideas from Alexander Lakhin's proposed patch, though it is
very different in detail.
Make sure that it considers all the possibilities that the old code did,
instead of trying only one possibility per character position. To keep the
runtime in bounds, instead tweak the character incrementers to not try
every possible multibyte character code. Remove unnecessary logic to
restore the old character value on failure. Additional comment and
formatting cleanup.
cash_out failed to handle multiple-byte thousands separators, as per bug
#6277 from Alexander Law. In addition, cash_in didn't handle that either,
nor could it handle multiple-byte positive_sign. Both routines failed to
support multiple-byte mon_decimal_point, which I did not think was worth
changing, but at least now they check for the possibility and fall back to
using '.' rather than emitting invalid output. Also, make cash_in handle
trailing negative signs, which formerly it would reject. Since cash_out
generates trailing negative signs whenever the locale tells it to, this
last omission represents a fail-to-reload-dumped-data bug. IMO that
justifies patching this all the way back.
This infrastructure doesn't in any way guarantee that the character
we produce will sort before the one we incremented; but it does at least
make it much more likely that we'll end up with something that is a valid
character, which improves our chances.
Kyotaro Horiguchi, with various adjustments by me.
We need not wait until the commit record is durably on disk, because
in the event of a crash the page we're updating with hint bits will
be gone anyway. Per off-list report from Heikki Linnakangas, this
can significantly degrade the performance of unlogged tables; I was
able to show a 2x speedup from this patch on a pgbench run with scale
factor 15. In practice, this will mostly help small, heavily updated
tables, because on larger tables you're unlikely to run into the same
row again before the commit record makes it out to disk.
one lock per backend or auxiliary process - the need for a lock for each
aux processes was not accounted for in NumLWLocks(). No-one noticed,
because the three locks needed for the three aux processes fit into the
few extra lwlocks we allocate for 3rd party modules that don't call
RequestAddinLWLocks() (NUM_USER_DEFINED_LWLOCKS, 4 by default).
If the right-hand side of a semijoin is unique, then we can treat it like a
normal join (or another way to say that is: we don't need to explicitly
unique-ify the data before doing it as a normal join). We were recognizing
such cases when the RHS was a sub-query with appropriate DISTINCT or GROUP
BY decoration, but there's another way: if the RHS is a plain relation with
unique indexes, we can check if any of the indexes prove the output is
unique. Most of the infrastructure for that was there already in the join
removal code, though I had to rearrange it a bit. Per reflection about a
recent example in pgsql-performance.
Use names like "RI_ConstraintTrigger_a_NNNN" for FK action triggers and
"RI_ConstraintTrigger_c_NNNN" for FK check triggers. This ensures the
action trigger fires first in self-referential cases where the very same
row update fires both an action and a check trigger. This change provides
a non-probabilistic solution for bug #6268, at the risk that it could break
client code that is making assumptions about the exact names assigned to
auto-generated FK triggers. Hence, change this in HEAD only. No need for
forced initdb since old triggers continue to work fine.
When a foreign-key constraint references another column of the same table,
row updates will queue both the PK's ON UPDATE action and the FK's CHECK
action in the same event. The ON UPDATE action must execute first, else
the CHECK will check a non-final state of the row and possibly throw an
inappropriate error, as seen in bug #6268 from Roman Lytovchenko.
Now, the firing order of multiple triggers for the same event is determined
by the sort order of their pg_trigger.tgnames, and the auto-generated names
we use for FK triggers are "RI_ConstraintTrigger_NNNN" where NNNN is the
trigger OID. So most of the time the firing order is the same as creation
order, and so rearranging the creation order fixes it.
This patch will fail to fix the problem if the OID counter wraps around or
adds a decimal digit (eg, from 99999 to 100000) while we are creating the
triggers for an FK constraint. Given the small odds of that, and the low
usage of self-referential FKs, we'll live with that solution in the back
branches. A better fix is to change the auto-generated names for FK
triggers, but it seems unwise to do that in stable branches because there
may be client code that depends on the naming convention. We'll fix it
that way in HEAD in a separate patch.
Back-patch to all supported branches, since this bug has existed for a long
time.
This allows different instances to use the eventlog with different
identifiers, by setting the event_source GUC, similar to how
syslog_ident works.
Original patch by MauMau, heavily modified by Magnus Hagander
The uniqueness condition might fail to hold intra-transaction, and assuming
it does can give incorrect query results. Per report from Marti Raudsepp,
though this is not his proposed patch.
Back-patch to 9.0, where both these features were introduced. In the
released branches, add the new IndexOptInfo field to the end of the struct,
to try to minimize ABI breakage for third-party code that may be examining
that struct.
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
No need to do "errcode(errcode_for_file_access())", just
"errcode_for_file_access()" is enough. The extra errcode() call is useless
but harmless, so there's no user-visible bug here. Nevertheless, backpatch
to 9.1 where this code were added.
Avoid possibly dumping core when pgstat_track_activity_query_size has a
less-than-default value; avoid uselessly searching for the query string
of a successfully-exited backend; don't bother putting out an ERRDETAIL if
we don't have a query to show; some other minor stylistic improvements.
Turns out that use of ShareUpdateExclusiveLock or ShareRowExclusiveLock
to protect DDL changes had gotten copied into several places that were
not touched by either of Simon's original patches for the feature, and
thus neither he nor I thought to revert them. (Indeed, it appears that
two of these uses were committed *after* the reversion, which just goes
to show that git merging is no panacea.) Change these places to use
AccessExclusiveLock again. If we ever manage to resurrect that feature,
we're going to have to think a bit harder about how to keep lock level
usage in sync for DDL operations that aren't within the AlterTable
infrastructure.
Two of these bugs are only in HEAD, but one is in the 9.1 branch too.
Alvaro found one of them, I found the other two.
To avoid minimize risk inside the postmaster, we subject this feature
to a number of significant limitations. We very much wish to avoid
doing any complex processing inside the postmaster, due to the
posssibility that the crashed backend has completely corrupted shared
memory. To that end, no encoding conversion is done; instead, we just
replace anything that doesn't look like an ASCII character with a
question mark. We limit the amount of data copied to 1024 characters,
and carefully sanity check the source of that data. While these
restrictions would doubtless be unacceptable in a general-purpose
logging facility, even this limited facility seems like an improvement
over the status quo ante.
Marti Raudsepp, reviewed by PDXPUG and myself
Essentially, the "IF EXISTS" portion was being ignored, and an error
thrown anyway if the opfamily did not exist.
I broke this in commit fd1843ff8979c0461fb3f1a9eab61140c977e32d; so
backpatch to 9.1.X.
Report and diagnosis by KaiGai Kohei.
There's no need to clamp the standby's xmin to be greater than
GetOldestXmin's result; if there were any such need this logic would be
hopelessly inadequate anyway, because it fails to account for
within-database versus cluster-wide values of GetOldestXmin. So get rid of
that, and just rely on sanity-checking that the xmin is not wrapped around
relative to the nextXid counter. Also, don't reset the walsender's xmin if
the current feedback xmin is indeed out of range; that just creates more
problems than we already had. Lastly, don't bother to take the
ProcArrayLock; there's no need to do that to set xmin.
Also improve the comments about this in GetOldestXmin itself.
extnamespace means something altogether different in this context.
Mostly by accident, this coding error (introduced in my commit
82a4a777d9) broke the buildfarm instead
of just silently doing the wrong thing.
This gets rid of a significant amount of duplicative code.
KaiGai Kohei, reviewed in earlier versions by Dimitri Fontaine, with
further review and cleanup by me.
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.
An empty HBA file is surely an error, since it means there is no way to
connect to the server. We've not heard identifiable reports of people
actually doing that, but this will also close off the case Thom Brown just
complained of, namely pointing hba_file at a directory. (On at least some
platforms with some directories, it will read as an empty file.)
Perhaps this should be back-patched, but given the lack of previous
complaints, I won't add extra work for the translators.
In general the data returned by an index-only scan should have the
datatypes originally computed by FormIndexDatum. If the index opclasses
use "storage" datatypes different from their input datatypes, the scan
tuple will not have the same rowtype attributed to the index; but we had
a hard-wired assumption that that was true in nodeIndexonlyscan.c. We'd
already hacked around the issue for the one case where the types are
different in btree indexes (btree name_ops), but this would definitely
come back to bite us if we ever implement index-only scans in GiST.
To fix, require the index AM to explicitly provide the tupdesc for the
tuple it is returning. btree can just pass back the index's tupdesc, but
GiST will have to work harder when and if it supports index-only scans.
I had previously proposed fixing this by allowing the index AM to fill the
scan tuple slot directly; but on reflection that seemed like a module
layering violation, since TupleTableSlots are creatures of the executor.
At least in the btree case, it would also be less efficient, since the
tuple deconstruction work would occur even for rows later found to be
invisible to the scan's snapshot.
This view was being insufficiently careful about matching the FK constraint
to the depended-on primary or unique key constraint. That could result in
failure to show an FK constraint at all, or showing it multiple times, or
claiming that it depended on a different constraint than the one it really
does. Fix by joining via pg_depend to ensure that we find only the correct
dependency.
Back-patch, but don't bump catversion because we can't force initdb in back
branches. The next minor-version release notes should explain that if you
need to fix this in an existing installation, you can drop the
information_schema schema then re-create it by sourcing
$SHAREDIR/information_schema.sql in each database (as a superuser of
course).
Add a column pg_class.relallvisible to remember the number of pages that
were all-visible according to the visibility map as of the last VACUUM
(or ANALYZE, or some other operations that update pg_class.relpages).
Use relallvisible/relpages, instead of an arbitrary constant, to estimate
how many heap page fetches can be avoided during an index-only scan.
This is pretty primitive and will no doubt see refinements once we've
acquired more field experience with the index-only scan mechanism, but
it's way better than using a constant.
Note: I had to adjust an underspecified query in the window.sql regression
test, because it was changing answers when the plan changed to use an
index-only scan. Some of the adjacent tests perhaps should be adjusted
as well, but I didn't do that here.
Nobody using the missing_ok flag yet, but let's speculate that this will
be a better interface for future callers.
KaiGai Kohei, with some adjustments by me.
Relation rowtypes and automatically-generated array types do not need to
have their own extension membership dependency entries. If we create such
then it becomes more difficult to remove items from an extension, and it's
also harder for an extension upgrade script to make sure it duplicates the
dependencies created by the extension's regular installation script.
I changed the code in such a way that this happened in commit
988cccc620, I think because of worries about
the shell-type-replacement case; but that cure was worse than the disease.
It would only matter if one extension created a shell type that was
replaced with an auto-generated type in another extension, which seems
pretty far-fetched. Better to make this work unsurprisingly in normal
cases.
Report and patch by Robert Haas, comment adjustments by me.
We have seen one too many reports of people trying to use 9.1 extension
files in the old-fashioned way of sourcing them in psql. Not only does
that usually not work (due to failure to substitute for MODULE_PATHNAME
and/or @extschema@), but if it did work they'd get a collection of loose
objects not an extension. To prevent this, insert an \echo ... \quit
line that prints a suitable error message into each extension script file,
and teach commands/extension.c to ignore lines starting with \echo.
That should not only prevent any adverse consequences of loading a script
file the wrong way, but make it crystal clear to users that they need to
do it differently now.
Tom Lane, following an idea of Andrew Dunstan's. Back-patch into 9.1
... there is not going to be much value in this if we wait till 9.2.
It's been bothering me for several days that pretending that the cstring
data stored in a btree name_ops column is really a "name" Datum could lead
to reading past the end of memory. However, given the current memory
layout used for index-only scans in the btree code, a crash is in fact not
possible. Document that so we don't break it. I have not thought of any
other solutions that aren't fairly ugly too, and most of them lose the
functionality of index-only scans on name columns altogether, so this seems
like the way to go.
Dept. of second thoughts: as long as we've got that tlist hanging around
anyway, we can apply ExecTypeFromTL to it to get a suitable descriptor for
the ScanTupleSlot. This is a nicer solution than the previous one because
it eliminates some hard-wired knowledge about btree name_ops, and because
it avoids the somewhat shaky assumption that we needn't set up the scan
tuple descriptor in EXPLAIN_ONLY mode. It doesn't change what actually
happens at run-time though, and I'm still a bit nervous about that.
Simon Riggs
Robert Haas
Tom Lane
Peter Eisentraut
Heikki Linnakangas
Magnus Hagander
Bruce Momjian