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Since WITH CHECK OPTION was introduced, ExecInitModifyTable has
initialized WCO expressions with the wrong plan node as parent -- that is,
it passed its input subplan not the ModifyTable node itself. Up to now
we thought this was harmless, but bug #16006 from Vinay Banakar shows it's
not: if the input node is a SubqueryScan then ExecInitWholeRowVar can get
confused into doing the wrong thing. (The fact that ExecInitWholeRowVar
contains such logic is certainly a horrid kluge that doesn't deserve to
live, but figuring out another way to do that is a task for some other day.)
Andres had already noticed the wrong-parent mistake and fixed it in commit
148e632c0, but not being aware of any user-visible consequences, he quite
reasonably didn't back-patch. This patch is simply a back-patch of
148e632c0, plus addition of a test case based on bug #16006. I also added
the test case to v12/HEAD, even though the bug is already fixed there.
Back-patch to all supported branches. 9.4 lacks RLS policies so the
new test case doesn't work there, but I'm pretty sure a test could be
devised based on using a whole-row Var in a plain WITH CHECK OPTION
condition. (I lack the cycles to do so myself, though.)
Andres Freund and Tom Lane
Discussion: https://postgr.es/m/16006-99290d2e4642cbd5@postgresql.org
Discussion: https://postgr.es/m/20181205225213.hiwa3kgoxeybqcqv@alap3.anarazel.de
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The stated reason for acquiring predicate locks on heap pages hasn't
existed since commit c01262a8, so fix the comment. Perhaps in a later
release we'll also be able to change the code to use tuple locks.
Back-patch all the way.
Reviewed-by: Ashwin Agrawal
Discussion: https://postgr.es/m/CAEepm%3D2GK3FVdnt5V3d%2Bh9njWipCv_fNL%3DwjxyUhzsF%3D0PcbNg%40mail.gmail.com
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When this code was initially introduced in commit d1b7c1ff, the structure
used was SharedPlanStateInstrumentation, but later when it got changed to
Instrumentation structure in commit b287df70, we forgot to update the
comment.
Reported-by: Wu Fei
Author: Wu Fei
Reviewed-by: Amit Kapila
Backpatch-through: 9.6
Discussion: https://postgr.es/m/52E6E0843B9D774C8C73D6CF64402F0562215EB2@G08CNEXMBPEKD02.g08.fujitsu.local
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Historically we forbade datatype-specific comparison functions from
returning INT_MIN, so that it would be safe to invert the sort order
just by negating the comparison result. However, this was never
really safe for comparison functions that directly return the result
of memcmp(), strcmp(), etc, as POSIX doesn't place any such restriction
on those library functions. Buildfarm results show that at least on
recent Linux on s390x, memcmp() actually does return INT_MIN sometimes,
causing sort failures.
The agreed-on answer is to remove this restriction and fix relevant
call sites to not make such an assumption; code such as "res = -res"
should be replaced by "INVERT_COMPARE_RESULT(res)". The same is needed
in a few places that just directly negated the result of memcmp or
strcmp.
To help find places having this problem, I've also added a compile option
to nbtcompare.c that causes some of the commonly used comparators to
return INT_MIN/INT_MAX instead of their usual -1/+1. It'd likely be
a good idea to have at least one buildfarm member running with
"-DSTRESS_SORT_INT_MIN". That's far from a complete test of course,
but it should help to prevent fresh introductions of such bugs.
This is a longstanding portability hazard, so back-patch to all supported
branches.
Discussion: https://postgr.es/m/20180928185215.ffoq2xrq5d3pafna@alap3.anarazel.de
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In a case where we have multiple relation-scan nodes in a cursor plan,
such as a scan of an inheritance tree, it's possible to fetch from a
given scan node, then rewind the cursor and fetch some row from an
earlier scan node. In such a case, execCurrent.c mistakenly thought
that the later scan node was still active, because ExecReScan hadn't
done anything to make it look not-active. We'd get some sort of
failure in the case of a SeqScan node, because the node's scan tuple
slot would be pointing at a HeapTuple whose t_self gets reset to
invalid by heapam.c. But it seems possible that for other relation
scan node types we'd actually return a valid tuple TID to the caller,
resulting in updating or deleting a tuple that shouldn't have been
considered current. To fix, forcibly clear the ScanTupleSlot in
ExecScanReScan.
Another issue here, which seems only latent at the moment but could
easily become a live bug in future, is that rewinding a cursor does
not necessarily lead to *immediately* applying ExecReScan to every
scan-level node in the plan tree. Upper-level nodes will think that
they can postpone that call if their child node is already marked
with chgParam flags. I don't see a way for that to happen today in
a plan tree that's simple enough for execCurrent.c's search_plan_tree
to understand, but that's one heck of a fragile assumption. So, add
some logic in search_plan_tree to detect chgParam flags being set on
nodes that it descended to/through, and assume that that means we
should consider lower scan nodes to be logically reset even if their
ReScan call hasn't actually happened yet.
Per bug #15395 from Matvey Arye. This has been broken for a long time,
so back-patch to all supported branches.
Discussion: https://postgr.es/m/153764171023.14986.280404050547008575@wrigleys.postgresql.org
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The EvalPlanQual machinery assumes that any initplans (that is,
uncorrelated sub-selects) used during an EPQ recheck would have already
been evaluated during the main query; this is implicit in the fact that
execPlan pointers are not copied into the EPQ estate's es_param_exec_vals.
But it's possible for that assumption to fail, if the initplan is only
reached conditionally. For example, a sub-select inside a CASE expression
could be reached during a recheck when it had not been previously, if the
CASE test depends on a column that was just updated.
This bug is old, appearing to date back to my rewrite of EvalPlanQual in
commit 9f2ee8f28, but was not detected until Kyle Samson reported a case.
To fix, force all not-yet-evaluated initplans used within the EPQ plan
subtree to be evaluated at the start of the recheck, before entering the
EPQ environment. This could be inefficient, if such an initplan is
expensive and goes unused again during the recheck --- but that's piling
one layer of improbability atop another. It doesn't seem worth adding
more complexity to prevent that, at least not in the back branches.
It was convenient to use the new-in-v11 ExecEvalParamExecParams function
to implement this, but I didn't like either its name or the specifics of
its API, so revise that.
Back-patch all the way. Rather than rewrite the patch to avoid depending
on bms_next_member() in the oldest branches, I chose to back-patch that
function into 9.4 and 9.3. (This isn't the first time back-patches have
needed that, and it exhausted my patience.) I also chose to back-patch
some test cases added by commits 71404af2a and 342a1ffa2 into 9.4 and 9.3,
so that the 9.x versions of eval-plan-qual.spec are all the same.
Andrew Gierth diagnosed the problem and contributed the added test cases,
though the actual code changes are by me.
Discussion: https://postgr.es/m/A033A40A-B234-4324-BE37-272279F7B627@tripadvisor.com
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This patch removes two sources of interference between nominally
independent functions when one SPI-using function calls another,
perhaps without knowing that it does so.
Chapman Flack pointed out that xml.c's query_to_xml_internal() expects
SPI_tuptable and SPI_processed to stay valid across datatype output
function calls; but it's possible that such a call could involve
re-entrant use of SPI. It seems likely that there are similar hazards
elsewhere, if not in the core code then in third-party SPI users.
Previously SPI_finish() reset SPI's API globals to zeroes/nulls, which
would typically make for a crash in such a situation. Restoring them
to the values they had at SPI_connect() seems like a considerably more
useful behavior, and it still meets the design goal of not leaving any
dangling pointers to tuple tables of the function being exited.
Also, cause SPI_connect() to reset these variables to zeroes/nulls after
saving them. This prevents interference in the opposite direction: it's
possible that a SPI-using function that's only ever been tested standalone
contains assumptions that these variables start out as zeroes. That was
the case as long as you were the outermost SPI user, but not so much for
an inner user. Now it's consistent.
Report and fix suggestion by Chapman Flack, actual patch by me.
Back-patch to all supported branches.
Discussion: https://postgr.es/m/9fa25bef-2e4f-1c32-22a4-3ad0723c4a17@anastigmatix.net
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When executing a SubPlan in an expression, the EState's direction
field was left alone, resulting in an attempt to execute the subplan
backwards if it was encountered during a backwards scan of a cursor.
Also, though much less likely, it was possible to reach the execution
of an InitPlan while in backwards-scan state.
Repair by saving/restoring estate->es_direction and forcing forward
scan mode in the relevant places.
Backpatch all the way, since this has been broken since 8.3 (prior to
commit c7ff7663e, SubPlans had their own EStates rather than sharing
the parent plan's, so there was no confusion over scan direction).
Per bug #15336 reported by Vladimir Baranoff; analysis and patch by
me, review by Tom Lane.
Discussion: https://postgr.es/m/153449812167.1304.1741624125628126322@wrigleys.postgresql.org
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Currently, we release the asynchronous resources as soon as it is evident
that no more rows will be needed e.g. when a Limit is filled. This can be
problematic especially for custom and foreign scans where we can scan
backward. Fix that by disallowing the shutting down of resources in such
cases.
Reported-by: Robert Haas
Analysed-by: Robert Haas and Amit Kapila
Author: Amit Kapila
Reviewed-by: Robert Haas
Backpatch-through: 9.6 where this code was introduced
Discussion: https://postgr.es/m/86137f17-1dfb-42f9-7421-82fd786b04a1@anayrat.info
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The buffer usage stats is accounted only for the execution phase of the
node. For Gather and Gather Merge nodes, such stats are accumulated at
the time of shutdown of workers which is done after execution of node due
to which we missed to account them for such nodes. Fix it by treating
nodes as running while we shut down them.
We can also miss accounting for a Limit node when Gather or Gather Merge
is beneath it, because it can finish the execution before shutting down
such nodes. So we allow a Limit node to shut down the resources before it
completes the execution.
In the passing fix the gather node code to allow workers to shut down as
soon as we find that all the tuples from the workers have been retrieved.
The original code use to do that, but is accidently removed by commit
01edb5c7fc.
Reported-by: Adrien Nayrat
Author: Amit Kapila and Robert Haas
Reviewed-by: Robert Haas and Andres Freund
Backpatch-through: 9.6 where this code was introduced
Discussion: https://postgr.es/m/86137f17-1dfb-42f9-7421-82fd786b04a1@anayrat.info
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In the leader backend, we don't track the buffer usage for ExecutorStart
phase whereas in worker backend we track it for ExecutorStart phase as
well. This leads to different value for buffer usage stats for the
parallel and non-parallel query. Change the code so that worker backend
also starts tracking buffer usage after ExecutorStart.
Author: Amit Kapila and Robert Haas
Reviewed-by: Robert Haas and Andres Freund
Backpatch-through: 9.6 where this code was introduced
Discussion: https://postgr.es/m/86137f17-1dfb-42f9-7421-82fd786b04a1@anayrat.info
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I was confused by what "intended to be parallel serially" meant, until
Robert Haas and David G. Johnston explained it. Rephrase the comment to
make it more clear, using David's suggested wording.
Discussion: https://www.postgresql.org/message-id/1fec9022-41e8-e484-70ce-2179b08c2092%40iki.fi
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A collection of typos I happened to spot while reading code, as well as
grepping for common mistakes.
Backpatch to all supported versions, as applicable, to avoid conflicts
when backporting other commits in the future.
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The impact of VARIADIC on the combine/serialize/deserialize support
functions of an aggregate wasn't thought through carefully. There is
actually no impact, because variadicity isn't passed through to these
functions (and it doesn't seem like it would need to be). However,
lookup_agg_function was mistakenly told to check things as though it were
passed through. The net result was that it was impossible to declare an
aggregate that had both VARIADIC input and parallelism support functions.
In passing, fix a runtime check in nodeAgg.c for the combine function's
strictness to make its error message agree with the creation-time check.
The previous message was actually backwards, and it doesn't seem like
there's a good reason to have two versions of this message text anyway.
Back-patch to 9.6 where parallel aggregation was introduced.
Alexey Bashtanov; message fix by me
Discussion: https://postgr.es/m/f86dde87-fef4-71eb-0480-62754aaca01b@imap.cc
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"UPDATE/DELETE WHERE CURRENT OF cursor_name" failed, with an error message
like "cannot extract system attribute from virtual tuple", if the cursor
was using a index-only scan for the target table. Fix it by digging the
current TID out of the indexscan state.
It seems likely that the same failure could occur for CustomScan plans
and perhaps some FDW plan types, so that leaving this to be treated as an
internal error with an obscure message isn't as good an idea as it first
seemed. Hence, add a bit of heaptuple.c infrastructure to let us deliver
a more on-topic message. I chose to make the message match what you get
for the case where execCurrentOf can't identify the target scan node at
all, "cursor "foo" is not a simply updatable scan of table "bar"".
Perhaps it should be different, but we can always adjust that later.
In the future, it might be nice to provide hooks that would let custom
scan providers and/or FDWs deal with this in other ways; but that's
not a suitable topic for a back-patchable bug fix.
It's been like this all along, so back-patch to all supported branches.
Yugo Nagata and Tom Lane
Discussion: https://postgr.es/m/20180201013349.937dfc5f.nagata@sraoss.co.jp
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ExecHashTableCreate allocated some memory that wasn't freed by
ExecHashTableDestroy, specifically the per-hash-key function information.
That's not a huge amount of data, but if one runs a query that repeats
a hash join enough times, it builds up. Fix by arranging for the data
in question to be kept in the hashtable's hashCxt instead of leaving it
"loose" in the query-lifespan executor context. (This ensures that we'll
also clean up anything that the hash functions allocate in fn_mcxt.)
Per report from Amit Khandekar. It's been like this forever, so back-patch
to all supported branches.
Discussion: https://postgr.es/m/CAJ3gD9cFofAWGvcxLOxDHC=B0hjtW8yGmUsF2hdGh97CM38=7g@mail.gmail.com
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An updating query that reads a CTE within an InitPlan or SubPlan could get
incorrect results if it updates rows that are concurrently being modified.
This is caused by CteScanNext supposing that nothing inside its recursive
ExecProcNode call could change which read pointer is selected in the CTE's
shared tuplestore. While that's normally true because of scoping
considerations, it can break down if an EPQ plan tree gets built during the
call, because EvalPlanQualStart builds execution trees for all subplans
whether they're going to be used during the recheck or not. And it seems
like a pretty shaky assumption anyway, so let's just reselect our own read
pointer here.
Per bug #14870 from Andrei Gorita. This has been broken since CTEs were
implemented, so back-patch to all supported branches.
Discussion: https://postgr.es/m/20171024155358.1471.82377@wrigleys.postgresql.org
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When a Gather or Gather Merge node is started and stopped multiple
times, accumulate instrumentation data only once, at the end, instead
of after each execution, to avoid recording inflated totals.
This is a back-port of commit 8526bcb2df76d5171b4f4d6dc7a97560a73a5eff
by Amit Kapila.
Discussion: http://postgr.es/m/20171127175631.GA405@depesz.com
Discussion: http://postgr.es/m/CAA4eK1KT3BYj50qWhK5qBF=LDzQCoUVSFZjcK3mHoJJeWA+fNA@mail.gmail.com
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I noticed that _SPI_execute_plan initially sets spierrcontext.arg = NULL,
and only fills it in some time later. If an error were to happen in
between, _SPI_error_callback would try to dereference the null pointer.
This is unlikely --- there's not much between those points except
push-snapshot calls --- but it's clearly not impossible. Tweak the
callback to do nothing if the pointer isn't set yet.
It's been like this for awhile, so back-patch to all supported branches.
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rewriteTargetListUD's processing is dependent on the relkind of the query's
target table. That was fine at the time it was made to act that way, even
for queries on inheritance trees, because all tables in an inheritance tree
would necessarily be plain tables. However, the 9.5 feature addition
allowing some members of an inheritance tree to be foreign tables broke the
assumption that rewriteTargetListUD's output tlist could be applied to all
child tables with nothing more than column-number mapping. This led to
visible failures if foreign child tables had row-level triggers, and would
also break in cases where child tables belonged to FDWs that used methods
other than CTID for row identification.
To fix, delay running rewriteTargetListUD until after the planner has
expanded inheritance, so that it is applied separately to the (already
mapped) tlist for each child table. We can conveniently call it from
preprocess_targetlist. Refactor associated code slightly to avoid the
need to heap_open the target relation multiple times during
preprocess_targetlist. (The APIs remain a bit ugly, particularly around
the point of which steps scribble on parse->targetList and which don't.
But avoiding such scribbling would require a change in FDW callback APIs,
which is more pain than it's worth.)
Also fix ExecModifyTable to ensure that "tupleid" is reset to NULL when
we transition from rows providing a CTID to rows that don't. (That's
really an independent bug, but it manifests in much the same cases.)
Add a regression test checking one manifestation of this problem, which
was that row-level triggers on a foreign child table did not work right.
Back-patch to 9.5 where the problem was introduced.
Etsuro Fujita, reviewed by Ildus Kurbangaliev and Ashutosh Bapat
Discussion: https://postgr.es/m/20170514150525.0346ba72@postgrespro.ru
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When nodeValuesscan.c was written, it was impossible to have a SubPlan in
VALUES --- any sub-SELECT there would have to be uncorrelated and thereby
would produce an InitPlan instead. We therefore took a shortcut in the
logic that throws away a ValuesScan's per-row expression evaluation data
structures. This was broken by the introduction of LATERAL however; a
sub-SELECT containing a lateral reference produces a correlated SubPlan.
The cleanest fix for this would be to give up the optimization of
discarding the expression eval state. But that still seems pretty
unappetizing for long VALUES lists. It seems to work to just prevent
the subexpressions from hooking into the ValuesScan node's subPlan
list, so let's do that and see how well it works. (If this breaks,
due to additional connections between the subexpressions and the outer
query structures, we might consider compromises like throwing away data
only for VALUES rows not containing SubPlans.)
Per bug #14924 from Christian Duta. Back-patch to 9.3 where LATERAL
was introduced.
Discussion: https://postgr.es/m/20171124120836.1463.5310@wrigleys.postgresql.org
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When strict aggregate combine functions, used in multi-stage/parallel
aggregation, returned NULL, we didn't check for that, invoking the
combine function with NULL the next round, despite it being strict.
The equivalent code invoking normal transition functions has a check
for that situation, which did not get copied in a7de3dc5c346. Fix the
bug by adding the equivalent check.
Based on a quick look I could not find any strict combine functions in
core actually returning NULL, and it doesn't seem very likely external
users have done so. So this isn't likely to have caused issues in
practice.
Add tests verifying transition / combine functions returning NULL is
tested.
Reported-By: Andres Freund
Author: Andres Freund
Discussion: https://postgr.es/m/20171121033642.7xvmjqrl4jdaaat3@alap3.anarazel.de
Backpatch: 9.6, where parallel aggregation was introduced
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It turns out we misdiagnosed what the real problem was. Revert the
previous changes, because they may have worse consequences going
forward. A better fix is forthcoming.
The simplistic test case is kept, though disabled.
Discussion: https://postgr.es/m/20171102112019.33wb7g5wp4zpjelu@alap3.anarazel.de
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If we try to run a parallel plan in serial mode because, for example,
it's going to be scanned via a cursor, but for some reason we're
already in parallel mode (for example because an outer query is
running in parallel), we'd incorrectly try to launch workers.
Fix by adding a flag to the EState, so that we can be certain that
ExecutePlan() and ExecGather()/ExecGatherMerge() will have the same
idea about whether we are executing serially or in parallel.
Report and fix by Amit Kapila with help from Kuntal Ghosh. A few
tweaks by me.
Discussion: http://postgr.es/m/CAA4eK1+_BuZrmVCeua5Eqnm4Co9DAXdM5HPAOE2J19ePbR912Q@mail.gmail.com
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If we merge the transition calculations for two different aggregates,
it's reasonable to assume that the transition function should not care
which of those Aggref structs it gets from AggGetAggref(). It is not
reasonable to make the same assumption about an aggregate final function,
however. Commit 804163bc2 broke this, as it will pass whichever Aggref
was first associated with the transition state in both cases.
This doesn't create an observable bug so far as the core system is
concerned, because the only existing uses of AggGetAggref() are in
ordered-set aggregates that happen to not pay attention to anything
but the input properties of the Aggref; and besides that, we disabled
sharing of transition calculations for OSAs yesterday. Nonetheless,
if some third-party code were using AggGetAggref() in a normal aggregate,
they would be entitled to call this a bug. Hence, back-patch the fix
to 9.6 where the problem was introduced.
In passing, improve some of the comments about transition state sharing.
Discussion: https://postgr.es/m/CAB4ELO5RZhOamuT9Xsf72ozbenDLLXZKSk07FiSVsuJNZB861A@mail.gmail.com
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This ought to work, but the built-in OSAs are not capable of coping,
because their final-functions destructively modify their transition
state (specifically, the contained tuplesort object). That was fine
when those functions were written, but commit 804163bc2 moved the
goalposts without telling orderedsetaggs.c.
We should fix the built-in OSAs to support this, but it will take
a little work, especially if we don't want to sacrifice performance
in the normal non-shared-state case. Given that it took a year after
9.6 release for anyone to notice this bug, we should not prioritize
sharable-state over nonsharable-state performance. And a proper fix
is likely to be more complicated than we'd want to back-patch, too.
Therefore, let's just put in this stop-gap patch to prevent nodeAgg.c
from choosing to use shared state for OSAs. We can revert it in HEAD
when we get a better fix.
Report from Lukas Eder, diagnosis by me, patch by David Rowley.
Back-patch to 9.6 where the problem was introduced.
Discussion: https://postgr.es/m/CAB4ELO5RZhOamuT9Xsf72ozbenDLLXZKSk07FiSVsuJNZB861A@mail.gmail.com
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The logical decoding functions do BeginInternalSubTransaction and
RollbackAndReleaseCurrentSubTransaction to clean up after themselves.
It turns out that AtEOSubXact_SPI has an unrecognized assumption that
we always need to cancel the active SPI operation in the SPI context
that surrounds the subtransaction (if there is one). That's true
when the RollbackAndReleaseCurrentSubTransaction call is coming from
the SPI-using function itself, but not when it's happening inside
some unrelated function invoked by a SPI query. In practice the
affected callers are the various PLs.
To fix, record the current subtransaction ID when we begin a SPI
operation, and clean up only if that ID is the subtransaction being
canceled.
Also, remove AtEOSubXact_SPI's assertion that it must have cleaned
up the surrounding SPI context's active tuptable. That's proven
wrong by the same test case.
Also clarify (or, if you prefer, reinterpret) the calling conventions
for _SPI_begin_call and _SPI_end_call. The memory context cleanup
in the latter means that these have always had the flavor of a matched
resource-management pair, but they weren't documented that way before.
Per report from Ben Chobot.
Back-patch to 9.4 where logical decoding came in. In principle,
the SPI changes should go all the way back, since the problem dates
back to commit 7ec1c5a86. But given the lack of field complaints
it seems few people are using internal subtransactions in this way.
So I don't feel a need to take any risks in 9.2/9.3.
Discussion: https://postgr.es/m/73FBA179-C68C-4540-9473-71E865408B15@silentmedia.com
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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 20b655224249 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
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Etsuro Fujita
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This back-patches commit 32470825d36d99a81347ee36c181d609c952c061
into 9.6, primarily to make buildfarm member culicidae happy.
Unlike the HEAD patch, avoid changing the existing API of
CreateParallelContext; instead we just switch to using
CreateParallelContextForExternalFunction, even for core functions.
Petr Jelinek, with a bunch of basically-cosmetic adjustments by me
Discussion: https://postgr.es/m/548f9c1d-eafa-e3fa-9da8-f0cc2f654e60@2ndquadrant.com
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From: Josh Soref <jsoref@gmail.com>
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The loops in ExecHashJoinNewBatch(), ExecHashIncreaseNumBatches(), and
ExecHashRemoveNextSkewBucket() are all capable of iterating over many
tuples without ever doing a CHECK_FOR_INTERRUPTS, so that the backend
might fail to respond to SIGINT or SIGTERM for an unreasonably long time.
Fix that. In the case of ExecHashJoinNewBatch(), it seems useful to put
the added CHECK_FOR_INTERRUPTS into ExecHashJoinGetSavedTuple() rather
than directly in the loop, because that will also ensure that both
principal code paths through ExecHashJoinOuterGetTuple() will do a
CHECK_FOR_INTERRUPTS, which seems like a good idea to avoid surprises.
Back-patch to all supported branches.
Tom Lane and Thomas Munro
Discussion: https://postgr.es/m/6044.1487121720@sss.pgh.pa.us
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Backpatch to all supported versions, where applicable, to make backpatching
of future fixes go more smoothly.
Josh Soref
Discussion: https://www.postgresql.org/message-id/CACZqfqCf+5qRztLPgmmosr-B0Ye4srWzzw_mo4c_8_B_mtjmJQ@mail.gmail.com
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A client copy can't work inside a function because the FE/BE wire protocol
doesn't support nesting of a COPY operation within query results. (Maybe
it could, but the protocol spec doesn't suggest that clients should support
this, and libpq for one certainly doesn't.)
In most PLs, this prohibition is enforced by spi.c, but SQL functions don't
use SPI. A comparison of _SPI_execute_plan() and init_execution_state()
shows that rejecting client COPY is the only discrepancy in what they
allow, so there's no other similar bugs.
This is an astonishingly ancient oversight, so back-patch to all supported
branches.
Report: https://postgr.es/m/BY2PR05MB2309EABA3DEFA0143F50F0D593780@BY2PR05MB2309.namprd05.prod.outlook.com
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When the input value to a CoerceToDomain expression node is a read-write
expanded datum, we should pass a read-only pointer to any domain CHECK
expressions and then return the original read-write pointer as the
expression result. Previously we were blindly passing the same pointer to
all the consumers of the value, making it possible for a function in CHECK
to modify or even delete the expanded value. (Since a plpgsql function
will absorb a passed-in read-write expanded array as a local variable
value, it will in fact delete the value on exit.)
A similar hazard of passing the same read-write pointer to multiple
consumers exists in domain_check() and in ExecEvalCase, so fix those too.
The fix requires adding MakeExpandedObjectReadOnly calls at the appropriate
places, which is simple enough except that we need to get the data type's
typlen from somewhere. For the domain cases, solve this by redefining
DomainConstraintRef.tcache as okay for callers to access; there wasn't any
reason for the original convention against that, other than not wanting the
API of typcache.c to be any wider than it had to be. For CASE, there's
no good solution except to add a syscache lookup during executor start.
Per bug #14472 from Marcos Castedo. Back-patch to 9.5 where expanded
values were introduced.
Discussion: https://postgr.es/m/15225.1482431619@sss.pgh.pa.us
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If a query contained two aggregates that could share the transition value,
we would correctly collect the input into a tuplesort only once, but
incorrectly run the transition function over the accumulated input twice,
in finalize_aggregates(). That caused a crash, when we tried to call
tuplesort_performsort() on an already-freed NULL tuplestore.
Backport to 9.6, where sharing of transition state and this bug were
introduced.
Analysis by Tom Lane.
Discussion: https://www.postgresql.org/message-id/ac5b0b69-744c-9114-6218-8300ac920e61@iki.fi
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Commit 4212cb73262bbdd164727beffa4c4744b4ead92d rendered a comment
in execMain.c incorrect. Per complaint from Tom Lane, repair.
Patch from Amit Kapila, per wording suggested by Tom Lane and me.
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Previously, a prepared statement created via a Parse message could get
a parallel plan, but one created with a PREPARE statement could not.
This state of affairs was due to confusion on my (rhaas) part: I
erroneously believed that a CREATE TABLE .. AS EXECUTE statement could
only be performed with a prepared statement by PREPARE, but in fact
one created by a Prepare message works just as well. Therefore, it
makes no sense to allow parallel query in one case but not the other.
To fix, allow parallel query with all prepared statements, but run
the parallel plan serially (i.e. without workers) in the case of
CREATE TABLE .. AS EXECUTE. Also, document this.
Amit Kapila and Tobias Bussman, plus an extra sentence of
documentation by me.
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The previously code worked OK as long as a Gather node was never
rescanned, or if it was rescanned, as long as it got at least as
many workers on rescan as it had originally. But if the number
of workers ever decreased on a rescan, then it could crash.
Andreas Seltenreich
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Thomas Munro
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In the previous coding, if an aggregate's transition function returned an
expanded array, nodeAgg.c and nodeWindowAgg.c would always copy it and thus
force it into the flat representation. This led to ping-ponging between
flat and expanded formats, which costs a lot. For an aggregate using
array_append as transition function, I measured about a 15X slowdown
compared to the pre-9.5 code, when working on simple int[] arrays.
Of course, the old code was already O(N^2) in this usage due to copying
flat arrays all the time, but it wasn't quite this inefficient.
To fix, teach nodeAgg.c and nodeWindowAgg.c to allow expanded transition
values without copying, so long as the transition function takes care to
return the transition value already properly parented under the aggcontext.
That puts a bit of extra responsibility on the transition function, but
doing it this way allows us to not need any extra logic in the fast path
of advance_transition_function (ie, with a pass-by-value transition value,
or with a modified-in-place pass-by-reference value). We already know
that that's a hot spot so I'm loath to add any cycles at all there. Also,
while only array_append currently knows how to follow this convention,
this solution allows other transition functions to opt-in without needing
to have a whitelist in the core aggregation code.
(The reason we would need a whitelist is that currently, if you pass a
R/W expanded-object pointer to an arbitrary function, it's allowed to do
anything with it including deleting it; that breaks the core agg code's
assumption that it should free discarded values. Returning a value under
aggcontext is the transition function's signal that it knows it is an
aggregate transition function and will play nice. Possibly the API rules
for expanded objects should be refined, but that would not be a
back-patchable change.)
With this fix, an aggregate using array_append is no longer O(N^2), so it's
much faster than pre-9.5 code rather than much slower. It's still a bit
slower than the bespoke infrastructure for array_agg, but the differential
seems to be only about 10%-20% rather than orders of magnitude.
Discussion: <6315.1477677885@sss.pgh.pa.us>
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INSERT ... ON CONFLICT (specifically ExecCheckHeapTupleVisible) contains
another example of this unsafe coding practice. It is much harder to get
a failure out of it than the case fixed in commit 6292c2339, because in
most scenarios any hint bits that could be set would have already been set
earlier in the command. However, Konstantin Knizhnik reported a failure
with a custom transaction manager, and it's clearly possible to get a
failure via a race condition in async-commit mode.
For lack of a reproducible example, no regression test case in this
commit.
I did some testing with Asserts added to tqual.c's functions, and can say
that running "make check-world" exposed these two bugs and no others.
The Asserts are messy enough that I've not added them to the code for now.
Report: <57EE93C8.8080504@postgrespro.ru>
Related-Discussion: <CAO3NbwOycQjt2Oqy2VW-eLTq2M5uGMyHnGm=RNga4mjqcYD7gQ@mail.gmail.com>
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A transaction that conflicts against itself, for example
INSERT INTO t(pk) VALUES (1),(1) ON CONFLICT DO NOTHING;
should behave the same regardless of isolation level. It certainly
shouldn't throw a serialization error, as retrying will not help.
We got this wrong due to the ON CONFLICT logic not considering the case,
as reported by Jason Dusek.
Core of this patch is by Peter Geoghegan (based on an earlier patch by
Thomas Munro), though I didn't take his proposed code refactoring for fear
that it might have unexpected side-effects. Test cases by Thomas Munro
and myself.
Report: <CAO3NbwOycQjt2Oqy2VW-eLTq2M5uGMyHnGm=RNga4mjqcYD7gQ@mail.gmail.com>
Related-Discussion: <57EE93C8.8080504@postgrespro.ru>
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The transfunction was told that its first argument and result were
of the window function output type, not the aggregate state type.
This'd only matter if the transfunction consults get_fn_expr_argtype,
which typically only polymorphic functions would do.
Although we have several regression tests around polymorphic aggs,
none of them detected this mistake --- in fact, they still didn't
fail when I injected the same mistake into nodeAgg.c. So add some
more tests covering both plain agg and window-function-agg cases.
Per report from Sebastian Luque. Back-patch to 9.6 where the error
was introduced (by sloppy refactoring in commit 804163bc2, looks like).
Report: <87int2qkat.fsf@gmail.com>
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ExecInitCteScan supposed that it didn't have to do anything to the extra
tuplestore read pointer it gets from tuplestore_alloc_read_pointer.
However, it needs this read pointer to be positioned at the start of the
tuplestore, while tuplestore_alloc_read_pointer is actually defined as
cloning the current position of read pointer 0. In normal situations
that accidentally works because we initialize the whole plan tree at once,
before anything gets read. But it fails in an EvalPlanQual recheck, as
illustrated in bug #14328 from Dima Pavlov. To fix, just forcibly rewind
the pointer after tuplestore_alloc_read_pointer. The cost of doing so is
negligible unless the tuplestore is already in TSS_READFILE state, which
wouldn't happen in normal cases. We could consider altering tuplestore's
API to make that case cheaper, but that would make for a more invasive
back-patch and it doesn't seem worth it.
This has been broken probably for as long as we've had CTEs, so back-patch
to all supported branches.
Discussion: <32468.1474548308@sss.pgh.pa.us>
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I found that half a dozen (nearly 5%) of our AllocSetContextCreate calls
had typos in the context-sizing parameters. While none of these led to
especially significant problems, they did create minor inefficiencies,
and it's now clear that expecting people to copy-and-paste those calls
accurately is not a great idea. Let's reduce the risk of future errors
by introducing single macros that encapsulate the common use-cases.
Three such macros are enough to cover all but two special-purpose contexts;
those two calls can be left as-is, I think.
While this patch doesn't in itself improve matters for third-party
extensions, it doesn't break anything for them either, and they can
gradually adopt the simplified notation over time.
In passing, change TopMemoryContext to use the default allocation
parameters. Formerly it could only be extended 8K at a time. That was
probably reasonable when this code was written; but nowadays we create
many more contexts than we did then, so that it's not unusual to have a
couple hundred K in TopMemoryContext, even without considering various
dubious code that sticks other things there. There seems no good reason
not to let it use growing blocks like most other contexts.
Back-patch to 9.6, mostly because that's still close enough to HEAD that
it's easy to do so, and keeping the branches in sync can be expected to
avoid some future back-patching pain. The bugs fixed by these changes
don't seem to be significant enough to justify fixing them further back.
Discussion: <21072.1472321324@sss.pgh.pa.us>
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ExecReScanAgg's check for whether it could re-use a previously calculated
hashtable neglected the possibility that the Agg node might reference
PARAM_EXEC Params that are not referenced by its input plan node. That's
okay if the Params are in upper tlist or qual expressions; but if one
appears in aggregate input expressions, then the hashtable contents need
to be recomputed when the Param's value changes.
To avoid unnecessary performance degradation in the case of a Param that
isn't within an aggregate input, add logic to the planner to determine
which Params are within aggregate inputs. This requires a new field in
struct Agg, but fortunately we never write plans to disk, so this isn't
an initdb-forcing change.
Per report from Jeevan Chalke. This has been broken since forever,
so back-patch to all supported branches.
Andrew Gierth, with minor adjustments by me
Report: <CAM2+6=VY8ykfLT5Q8vb9B6EbeBk-NGuLbT6seaQ+Fq4zXvrDcA@mail.gmail.com>
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Commit af33039317ddc4a0e38a02e2255c2bf453115fd2 aimed to reduce
leakage from tqueue.c, which is good. Unfortunately, by changing the
memory context in which all of gather_readnext() executes, it also
changed the context in which ExecShutdownGatherWorkers executes, which
is not good, because that function eventually causes a call to
ExecParallelRetrieveInstrumentation, which proceeds to allocate
planstate->worker_instrument in a short-lived context, causing a
crash.
Rushabh Lathia, reviewed by Amit Kapila and by me.
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Per discussion, we should provide such functions to replace the lost
ability to discover AM properties by inspecting pg_am (cf commit
65c5fcd35). The added functionality is also meant to displace any code
that was looking directly at pg_index.indoption, since we'd rather not
believe that the bit meanings in that field are part of any client API
contract.
As future-proofing, define the SQL API to not assume that properties that
are currently AM-wide or index-wide will remain so unless they logically
must be; instead, expose them only when inquiring about a specific index
or even specific index column. Also provide the ability for an index
AM to override the behavior.
In passing, document pg_am.amtype, overlooked in commit 473b93287.
Andrew Gierth, with kibitzing by me and others
Discussion: <87mvl5on7n.fsf@news-spur.riddles.org.uk>
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Commit 874fe3aea changed the command tag returned for CREATE MATVIEW/CREATE
TABLE AS ... WITH NO DATA, but missed that there was code in spi.c that
expected the command tag to always be "SELECT". Fortunately, the
consequence was only an Assert failure, so this oversight should have no
impact in production builds.
Since this code path was evidently un-exercised, add a regression test.
Per report from Shivam Saxena. Back-patch to 9.3, like the previous commit.
Michael Paquier
Report: <97218716-480B-4527-B5CD-D08D798A0C7B@dresources.com>
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