| Commit message (Collapse) | Author | Age |
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ExecOpenScanRelation assumed that any relation listed in the ExecRowMark
list has been locked by InitPlan; but this is not true if the rel's
markType is ROW_MARK_COPY, which is possible if it's a foreign table.
In most (possibly all) cases, failure to acquire a lock here isn't really
problematic because the parser, planner, or plancache would have taken the
appropriate lock already. In principle though it might leave us vulnerable
to working with a relation that we hold no lock on, and in any case if the
executor isn't depending on previously-taken locks otherwise then it should
not do so for ROW_MARK_COPY relations.
Noted by Etsuro Fujita. Back-patch to all active versions, since the
inconsistency has been there a long time. (It's almost certainly
irrelevant in 9.0, since that predates foreign tables, but the code's
still wrong on its own terms.)
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The ROW_MARK_COPY path in EvalPlanQualFetchRowMarks() was just setting
tableoid to InvalidOid, I think on the assumption that the referenced
RTE must be a subquery or other case without a meaningful OID. However,
foreign tables also use this code path, and they do have meaningful
table OIDs; so failure to set the tuple field can lead to user-visible
misbehavior. Fix that by fetching the appropriate OID from the range
table.
There's still an issue about whether CTID can ever have a meaningful
value in this case; at least with postgres_fdw foreign tables, it does.
But that is a different problem that seems to require a significantly
different patch --- it's debatable whether postgres_fdw really wants to
use this code path at all.
Simplified version of a patch by Etsuro Fujita, who also noted the
problem to begin with. The issue can be demonstrated in all versions
having FDWs, so back-patch to 9.1.
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In commit bf7ca15875988a88e97302e012d7c4808bef3ea9 I introduced an
assumption that an RTE referenced by a whole-row Var must have a valid eref
field. This is false for RTEs constructed by DoCopy, and there are other
places taking similar shortcuts. Perhaps we should make all those places
go through addRangeTableEntryForRelation or its siblings instead of having
ad-hoc logic, but the most reliable fix seems to be to make the new code in
ExecEvalWholeRowVar cope if there's no eref. We can reasonably assume that
there's no need to insert column aliases if no aliases were provided.
Add a regression test case covering this, and also verifying that a sane
column name is in fact available in this situation.
Although the known case only crashes in 9.4 and HEAD, it seems prudent to
back-patch the code change to 9.2, since all the ingredients for a similar
failure exist in the variant patch applied to 9.3 and 9.2.
Per report from Jean-Pierre Pelletier.
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While building error messages to return to the user,
BuildIndexValueDescription, ExecBuildSlotValueDescription and
ri_ReportViolation would happily include the entire key or entire row in
the result returned to the user, even if the user didn't have access to
view all of the columns being included.
Instead, include only those columns which the user is providing or which
the user has select rights on. If the user does not have any rights
to view the table or any of the columns involved then no detail is
provided and a NULL value is returned from BuildIndexValueDescription
and ExecBuildSlotValueDescription. Note that, for key cases, the user
must have access to all of the columns for the key to be shown; a
partial key will not be returned.
Back-patch all the way, as column-level privileges are now in all
supported versions.
This has been assigned CVE-2014-8161, but since the issue and the patch
have already been publicized on pgsql-hackers, there's no point in trying
to hide this commit.
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Up to now, the "child" executor state trees generated for EvalPlanQual
rechecks have simply shared the ResultRelInfo arrays used for the original
execution tree. However, this leads to dangling-pointer problems, because
ExecInitModifyTable() is all too willing to scribble on some fields of the
ResultRelInfo(s) even when it's being run in one of those child trees.
This trashes those fields from the perspective of the parent tree, because
even if the generated subtree is logically identical to what was in use in
the parent, it's in a memory context that will go away when we're done
with the child state tree.
We do however want to share information in the direction from the parent
down to the children; in particular, fields such as es_instrument *must*
be shared or we'll lose the stats arising from execution of the children.
So the simplest fix is to make a copy of the parent's ResultRelInfo array,
but not copy any fields back at end of child execution.
Per report from Manuel Kniep. The added isolation test is based on his
example. In an unpatched memory-clobber-enabled build it will reliably
fail with "ctid is NULL" errors in all branches back to 9.1, as a
consequence of junkfilter->jf_junkAttNo being overwritten with $7f7f.
This test cannot be run as-is before that for lack of WITH syntax; but
I have no doubt that some variant of this problem can arise in older
branches, so apply the code change all the way back.
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In READ COMMITTED mode, if a SELECT FOR UPDATE discovers it has to redo
WHERE-clause checking on rows that have been updated since the SELECT's
snapshot, it invokes EvalPlanQual processing to do that. If this first
occurs within a non-first child table of an inheritance tree, the previous
coding could accidentally re-return a matching row from an earlier,
already-scanned child table. (And, to add insult to injury, I think this
could make it miss returning a row that should have been returned, if the
updated row that this happens on should still have passed the WHERE qual.)
Per report from Kyotaro Horiguchi; the added isolation test is based on his
test case.
This has been broken for quite awhile, so back-patch to all supported
branches.
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This only happens if a client issues a Parse message with an empty query
string, which is a bit odd; but since it is explicitly called out as legal
by our FE/BE protocol spec, we'd probably better continue to allow it.
Fix by adding tests everywhere that the raw_parse_tree field is passed to
functions that don't or shouldn't accept NULL. Also make it clear in the
relevant comments that NULL is an expected case.
This reverts commits a73c9dbab0165b3395dfe8a44a7dfd16166963c4 and
2e9650cbcff8c8fb0d9ef807c73a44f241822eee, which fixed specific crash
symptoms by hacking things at what now seems to be the wrong end, ie the
callee functions. Making the callees allow NULL is superficially more
robust, but it's not always true that there is a defensible thing for the
callee to do in such cases. The caller has more context and is better
able to decide what the empty-query case ought to do.
Per followup discussion of bug #11335. Back-patch to 9.2. The code
before that is sufficiently different that it would require development
of a separate patch, which doesn't seem worthwhile for what is believed
to be an essentially cosmetic change.
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At one time it wasn't terribly important what column names were associated
with the fields of a composite Datum, but since the introduction of
operations like row_to_json(), it's important that looking up the rowtype
ID embedded in the Datum returns the column names that users would expect.
However, that doesn't work terribly well: you could get the column names
of the underlying table, or column aliases from any level of the query,
depending on minor details of the plan tree. You could even get totally
empty field names, which is disastrous for cases like row_to_json().
It seems unwise to change this behavior too much in stable branches,
however, since users might not have noticed that they weren't getting
the least-unintuitive choice of field names. Therefore, in the back
branches, only change the results when the child plan has returned an
actually-empty field name. (We assume that can't happen with a named
rowtype, so this also dodges the issue of possibly producing RECORD-typed
output from a Var with a named composite result type.) As in the sister
patch for HEAD, we can get a better name to use from the Var's
corresponding RTE. There is no need to touch the RowExpr code since it
was already using a copy of the RTE's alias list for RECORD cases.
Back-patch as far as 9.2. Before that we did not have row_to_json()
so there were no core functions potentially affected by bogus field
names. While 9.1 and earlier do have contrib's hstore(record) which
is also affected, those versions don't seem to produce empty field names
(at least not in the known problem cases), so we'll leave them alone.
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ExecEvalWholeRowVar incorrectly supposed that it could "bless" the source
TupleTableSlot just once per query. But if the input is coming from an
Append (or, perhaps, other cases?) more than one slot might be returned
over the query run. This led to "record type has not been registered"
errors when a composite datum was extracted from a non-blessed slot.
This bug has been there a long time; I guess it escaped notice because when
dealing with subqueries the planner tends to expand whole-row Vars into
RowExprs, which don't have the same problem. It is possible to trigger
the problem in all active branches, though, as illustrated by the added
regression test.
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ExecMakeTableFunctionResult evaluated the arguments for a function-in-FROM
in the query-lifespan memory context. This is insignificant in simple
cases where the function relation is scanned only once; but if the function
is in a sub-SELECT or is on the inside of a nested loop, any memory
consumed during argument evaluation can add up quickly. (The potential for
trouble here had been foreseen long ago, per existing comments; but we'd
not previously seen a complaint from the field about it.) To fix, create
an additional temporary context just for this purpose.
Per an example from MauMau. Back-patch to all active branches.
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This was not changed in HEAD, but will be done later as part of a
pgindent run. Future pgindent runs will also do this.
Report by Tom Lane
Backpatch through all supported branches, but not HEAD
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If we have an array of records stored on disk, the individual record fields
cannot contain out-of-line TOAST pointers: the tuptoaster.c mechanisms are
only prepared to deal with TOAST pointers appearing in top-level fields of
a stored row. The same applies for ranges over composite types, nested
composites, etc. However, the existing code only took care of expanding
sub-field TOAST pointers for the case of nested composites, not for other
structured types containing composites. For example, given a command such
as
UPDATE tab SET arraycol = ARRAY[(ROW(x,42)::mycompositetype] ...
where x is a direct reference to a field of an on-disk tuple, if that field
is long enough to be toasted out-of-line then the TOAST pointer would be
inserted as-is into the array column. If the source record for x is later
deleted, the array field value would become a dangling pointer, leading
to errors along the line of "missing chunk number 0 for toast value ..."
when the value is referenced. A reproducible test case for this was
provided by Jan Pecek, but it seems likely that some of the "missing chunk
number" reports we've heard in the past were caused by similar issues.
Code-wise, the problem is that PG_DETOAST_DATUM() is not adequate to
produce a self-contained Datum value if the Datum is of composite type.
Seen in this light, the problem is not just confined to arrays and ranges,
but could also affect some other places where detoasting is done in that
way, for example form_index_tuple().
I tried teaching the array code to apply toast_flatten_tuple_attribute()
along with PG_DETOAST_DATUM() when the array element type is composite,
but this was messy and imposed extra cache lookup costs whether or not any
TOAST pointers were present, indeed sometimes when the array element type
isn't even composite (since sometimes it takes a typcache lookup to find
that out). The idea of extending that approach to all the places that
currently use PG_DETOAST_DATUM() wasn't attractive at all.
This patch instead solves the problem by decreeing that composite Datum
values must not contain any out-of-line TOAST pointers in the first place;
that is, we expand out-of-line fields at the point of constructing a
composite Datum, not at the point where we're about to insert it into a
larger tuple. This rule is applied only to true composite Datums, not
to tuples that are being passed around the system as tuples, so it's not
as invasive as it might sound at first. With this approach, the amount
of code that has to be touched for a full solution is greatly reduced,
and added cache lookup costs are avoided except when there actually is
a TOAST pointer that needs to be inlined.
The main drawback of this approach is that we might sometimes dereference
a TOAST pointer that will never actually be used by the query, imposing a
rather large cost that wasn't there before. On the other side of the coin,
if the field value is used multiple times then we'll come out ahead by
avoiding repeat detoastings. Experimentation suggests that common SQL
coding patterns are unaffected either way, though. Applications that are
very negatively affected could be advised to modify their code to not fetch
columns they won't be using.
In future, we might consider reverting this solution in favor of detoasting
only at the point where data is about to be stored to disk, using some
method that can drill down into multiple levels of nested structured types.
That will require defining new APIs for structured types, though, so it
doesn't seem feasible as a back-patchable fix.
Note that this patch changes HeapTupleGetDatum() from a macro to a function
call; this means that any third-party code using that macro will not get
protection against creating TOAST-pointer-containing Datums until it's
recompiled. The same applies to any uses of PG_RETURN_HEAPTUPLEHEADER().
It seems likely that this is not a big problem in practice: most of the
tuple-returning functions in core and contrib produce outputs that could
not possibly be toasted anyway, and the same probably holds for third-party
extensions.
This bug has existed since TOAST was invented, so back-patch to all
supported branches.
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Given a composite-type parameter named x, "$1.*" worked fine, but "x.*"
not so much. This has been broken since named parameter references were
added in commit 9bff0780cf5be2193a5bad0d3df2dbe143085264, so patch back
to 9.2. Per bug #9085 from Hardy Falk.
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In commit c1352052ef1d4eeb2eb1d822a207ddc2d106cb13, I implemented an
optimization that assumed that a function's argument expressions would
either always return a set (ie multiple rows), or always not. This is
wrong however: we allow CASE expressions in which some arms return a set
of some type and others just return a scalar of that type. There may be
other examples as well. To fix, replace the run-time test of whether an
argument returned a set with a static precheck (expression_returns_set).
This adds a little bit of query startup overhead, but it seems barely
measurable.
Per bug #8228 from David Johnston. This has been broken since 8.0,
so patch all supported branches.
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ExecBuildSlotValueDescription() printed "null" for each dropped column in
a row being complained of by ExecConstraints(). This has some sanity in
terms of the underlying implementation, but is of course pretty surprising
to users. To fix, we must pass the target relation's descriptor to
ExecBuildSlotValueDescription(), because the slot descriptor it had been
using doesn't get labeled with attisdropped markers.
Per bug #8408 from Maxim Boguk. Back-patch to 9.2 where the feature of
printing row values in NOT NULL and CHECK constraint violation messages
was introduced.
Michael Paquier and Tom Lane
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Historically, printtup() has assumed that it could prevent memory leakage
by pfree'ing the string result of each output function and manually
managing detoasting of toasted values. This amounts to assuming that
datatype output functions never leak any memory internally; an assumption
we've already decided to be bogus elsewhere, for example in COPY OUT.
range_out in particular is known to leak multiple kilobytes per call, as
noted in bug #8573 from Godfried Vanluffelen. While we could go in and fix
that leak, it wouldn't be very notationally convenient, and in any case
there have been and undoubtedly will again be other leaks in other output
functions. So what seems like the best solution is to run the output
functions in a temporary memory context that can be reset after each row,
as we're doing in COPY OUT. Some quick experimentation suggests this is
actually a tad faster than the retail pfree's anyway.
This patch fixes all the variants of printtup, except for debugtup()
which is used in standalone mode. It doesn't seem worth worrying
about query-lifespan leaks in standalone mode, and fixing that case
would be a bit tedious since debugtup() doesn't currently have any
startup or shutdown functions.
While at it, remove manual detoast management from several other
output-function call sites that had copied it from printtup(). This
doesn't make a lot of difference right now, but in view of recent
discussions about supporting "non-flattened" Datums, we're going to
want that code gone eventually anyway.
Back-patch to 9.2 where range_out was introduced. We might eventually
decide to back-patch this further, but in the absence of known major
leaks in older output functions, I'll refrain for now.
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When RETURNING is specified, ExecDelete would return a virtual-tuple slot
that could contain pointers into an already-unpinned disk buffer. Another
process could change the buffer contents before we get around to using the
data, resulting in garbage results or even a crash. This seems of fairly
low probability, which may explain why there are no known field reports of
the problem, but it's definitely possible. Fix by forcing the result slot
to be "materialized" before we release pin on the disk buffer.
Back-patch to 9.0; in earlier branches there is no bug because
ExecProcessReturning sent the tuple to the destination immediately. Also,
this is already fixed in HEAD as part of the writable-foreign-tables patch
(where the fix is necessary for DELETE RETURNING to work at all with
postgres_fdw).
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fmgr_sql had been designed on the assumption that the FmgrInfo it's called
with has only query lifespan. This is demonstrably unsafe in connection
with range types, as shown in bug #7881 from Andrew Gierth. Fix things
so that we re-generate the function's cache data if the (sub)transaction
it was made in is no longer active.
Back-patch to 9.2. This might be needed further back, but it's not clear
whether the case can realistically arise without range types, so for now
I'll desist from back-patching further.
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Commit af7914c6627bcf0b0ca614e9ce95d3f8056602bf, which added the TIMING
option to EXPLAIN, had an oversight: if the TIMING option is disabled
then control in InstrStartNode() goes through an elog(DEBUG2) call, which
typically does nothing but takes a noticeable amount of time to do it.
Tweak the logic to avoid that.
In HEAD, also change the elog(DEBUG2)'s in instrument.c to elog(ERROR).
It's not very clear why they weren't like that to begin with, but this
episode shows that not complaining more vociferously about misuse is
likely to do little except allow bugs to remain hidden.
While at it, adjust some code that was making possibly-dangerous
assumptions about flag bits being in the rightmost byte of the
instrument_options word.
Problem reported by Pavel Stehule (via Tomas Vondra).
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exec_simple_check_plan and exec_eval_simple_expr attempted to call
GetCachedPlan directly. This meant that if an error was thrown during
planning, the resulting context traceback would not include the line
normally contributed by _SPI_error_callback. This is already inconsistent,
but just to be really odd, a re-execution of the very same expression
*would* show the additional context line, because we'd already have cached
the plan and marked the expression as non-simple.
The problem is easy to demonstrate in 9.2 and HEAD because planning of a
cached plan doesn't occur at all until GetCachedPlan is done. In earlier
versions, it could only be an issue if initial planning had succeeded, then
a replan was forced (already somewhat improbable for a simple expression),
and the replan attempt failed. Since the issue is mainly cosmetic in older
branches anyway, it doesn't seem worth the risk of trying to fix it there.
It is worth fixing in 9.2 since the instability of the context printout can
affect the results of GET STACKED DIAGNOSTICS, as per a recent discussion
on pgsql-novice.
To fix, introduce a SPI function that wraps GetCachedPlan while installing
the correct callback function. Use this instead of calling GetCachedPlan
directly from plpgsql.
Also introduce a wrapper function for extracting a SPI plan's
CachedPlanSource list. This lets us stop including spi_priv.h in
pl_exec.c, which was never a very good idea from a modularity standpoint.
In passing, fix a similar inconsistency that could occur in SPI_cursor_open,
which was also calling GetCachedPlan without setting up a context callback.
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Since 9.0, the count parameter has only limited the number of tuples
actually returned by the executor. It doesn't affect the behavior of
INSERT/UPDATE/DELETE unless RETURNING is specified, because without
RETURNING, the ModifyTable plan node doesn't return control to execMain.c
for each tuple. And we only check the limit at the top level.
While this behavioral change was unintentional at the time, discussion of
bug #6572 led us to the conclusion that we prefer the new behavior anyway,
and so we should just adjust the docs to match rather than change the code.
Accordingly, do that. Back-patch as far as 9.0 so that the docs match the
code in each branch.
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SPI_execute() and related functions create a CachedPlan, execute it once,
and immediately discard it, so that the functionality offered by
plancache.c is of no value in this code path. And performance measurements
show that the extra data copying and invalidation checking done by
plancache.c slows down simple queries by 10% or more compared to 9.1.
However, enough of the SPI code is shared with functions that do need plan
caching that it seems impractical to bypass plancache.c altogether.
Instead, let's invent a variant version of cached plans that preserves
99% of the API but doesn't offer any of the actual functionality, nor the
overhead. This puts SPI_execute() performance back on par, or maybe even
slightly better, than it was before. This change should resolve recent
complaints of performance degradation from Dong Ye, Pavel Stehule, and
others.
By avoiding data copying, this change also reduces the amount of memory
needed to execute many-statement SPI_execute() strings, as for instance in
a recent complaint from Tomas Vondra.
An additional benefit of this change is that multi-statement SPI_execute()
query strings are now processed fully serially, that is we complete
execution of earlier statements before running parse analysis and planning
on following ones. This eliminates a long-standing POLA violation, in that
DDL that affects the behavior of a later statement will now behave as
expected.
Back-patch to 9.2, since this was a performance regression compared to 9.1.
(In 9.2, place the added struct fields so as to avoid changing the offsets
of existing fields.)
Heikki Linnakangas and Tom Lane
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The dynahash code requires the number of buckets in a hash table to fit
in an int; but since we calculate the desired hash table size dynamically,
there are various scenarios where we might calculate too large a value.
The resulting overflow can lead to infinite loops, division-by-zero
crashes, etc. I (tgl) had previously installed some defenses against that
in commit 299d1716525c659f0e02840e31fbe4dea3, but that covered only one
call path. Moreover it worked by limiting the request size to work_mem,
but in a 64-bit machine it's possible to set work_mem high enough that the
problem appears anyway. So let's fix the problem at the root by installing
limits in the dynahash.c functions themselves.
Trouble report and patch by Jeff Davis.
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Commit 8cb53654dbdb4c386369eb988062d0bbb6de725e, which introduced DROP
INDEX CONCURRENTLY, managed to break CREATE INDEX CONCURRENTLY via a poor
choice of catalog state representation. The pg_index state for an index
that's reached the final pre-drop stage was the same as the state for an
index just created by CREATE INDEX CONCURRENTLY. This meant that the
(necessary) change to make RelationGetIndexList ignore about-to-die indexes
also made it ignore freshly-created indexes; which is catastrophic because
the latter do need to be considered in HOT-safety decisions. Failure to
do so leads to incorrect index entries and subsequently wrong results from
queries depending on the concurrently-created index.
To fix, make the final state be indisvalid = true and indisready = false,
which is otherwise nonsensical. This is pretty ugly but we can't add
another column without forcing initdb, and it's too late for that in 9.2.
(There's a cleaner fix in HEAD.)
In addition, change CREATE/DROP INDEX CONCURRENTLY so that the pg_index
flag changes they make without exclusive lock on the index are made via
heap_inplace_update() rather than a normal transactional update. The
latter is not very safe because moving the pg_index tuple could result in
concurrent SnapshotNow scans finding it twice or not at all, thus possibly
resulting in index corruption. This is a pre-existing bug in CREATE INDEX
CONCURRENTLY, which was copied into the DROP code.
In addition, fix various places in the code that ought to check to make
sure that the indexes they are manipulating are valid and/or ready as
appropriate. These represent bugs that have existed since 8.2, since
a failed CREATE INDEX CONCURRENTLY could leave a corrupt or invalid
index behind, and we ought not try to do anything that might fail with
such an index.
Also fix RelationReloadIndexInfo to ensure it copies all the pg_index
columns that are allowed to change after initial creation. Previously we
could have been left with stale values of some fields in an index relcache
entry. It's not clear whether this actually had any user-visible
consequences, but it's at least a bug waiting to happen.
In addition, do some code and docs review for DROP INDEX CONCURRENTLY;
some cosmetic code cleanup but mostly addition and revision of comments.
Portions of this need to be back-patched even further, but I'll work
on that separately.
Problem reported by Amit Kapila, diagnosis by Pavan Deolasee,
fix by Tom Lane and Andres Freund.
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This reverts commit d573e239f03506920938bf0be56c868d9c3416da, "Take fewer
snapshots". While that seemed like a good idea at the time, it caused
execution to use a snapshot that had been acquired before locking any of
the tables mentioned in the query. This created user-visible anomalies
that were not present in any prior release of Postgres, as reported by
Tomas Vondra. While this whole area could do with a redesign (since there
are related cases that have anomalies anyway), it doesn't seem likely that
any future patch would be reasonably back-patchable; and we don't want 9.2
to exhibit a behavior that's subtly unlike either past or future releases.
Hence, revert to prior code while we rethink the problem.
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When hashing a subplan like "WHERE (a, b) NOT IN (SELECT x, y FROM ...)",
findPartialMatch() attempted to match rows using the hashtable's internal
equality operators, which of course are for x and y's datatypes. What we
need to use are the potentially cross-type operators for a=x, b=y, etc.
Failure to do that leads to wrong answers or even crashes. The scope for
problems is limited to cases where we have different types with compatible
hash functions (else we'd not be using a hashed subplan), but for example
int4 vs int8 can cause the problem.
Per bug #7597 from Bo Jensen. This has been wrong since the hashed-subplan
code was written, so patch all the way back.
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Serializable Snapshot Isolation used for serializable transactions
depends on acquiring SIRead locks on all heap relation tuples which
are used to generate the query result, so that a later delete or
update of any of the tuples can flag a read-write conflict between
transactions. This is normally handled in heapam.c, with tuple level
locking. Since an index-only scan avoids heap access in many cases,
building the result from the index tuple, the necessary predicate
locks were not being acquired for all tuples in an index-only scan.
To prevent problems with tuple IDs which are vacuumed and re-used
while the transaction still matters, the xmin of the tuple is part of
the tag for the tuple lock. Since xmin is not available to the
index-only scan for result rows generated from the index tuples, it
is not possible to acquire a tuple-level predicate lock in such
cases, in spite of having the tid. If we went to the heap to get the
xmin value, it would no longer be an index-only scan. Rather than
prohibit index-only scans under serializable transaction isolation,
we acquire an SIRead lock on the page containing the tuple, when it
was not necessary to visit the heap for other reasons.
Backpatch to 9.2.
Kevin Grittner and Tom Lane
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The previous coding essentially assumed that nodes would be rescanned in
the same order they were initialized in; or at least that the "leader" of
a group of CTEscans would be rescanned before any others were required to
execute. Unfortunately, that isn't even a little bit true. It's possible
to devise queries in which the leader isn't rescanned until other CTEscans
on the same CTE have run to completion, or even in which the leader never
gets a rescan call at all.
The fix makes the leader specially responsible only for initial creation
and final destruction of the tuplestore; rescan resets are now a
symmetrically shared responsibility. This means that we might reset the
tuplestore multiple times when restarting a plan subtree containing
multiple CTEscans; but resetting an already-empty tuplestore is cheap
enough that that doesn't seem like a problem.
Per report from Adam Mackler; the new regression test cases are based on
his example query.
Back-patch to 8.4 where CTE scans were introduced.
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When a whole-row Var is reading the result of a subquery, we need it to
ignore any "resjunk" columns that the subquery might have evaluated for
GROUP BY or ORDER BY purposes. We've hacked this area before, in commit
68e40998d058c1f6662800a648ff1e1ce5d99cba, but that fix only covered
whole-row Vars of named composite types, not those of RECORD type; and it
was mighty klugy anyway, since it just assumed without checking that any
extra columns in the result must be resjunk. A proper fix requires getting
hold of the subquery's targetlist so we can actually see which columns are
resjunk (whereupon we can use a JunkFilter to get rid of them). So bite
the bullet and add some infrastructure to make that possible.
Per report from Andrew Dunstan and additional testing by Merlin Moncure.
Back-patch to all supported branches. In 8.3, also back-patch commit
292176a118da6979e5d368a4baf27f26896c99a5, which for some reason I had
not done at the time, but it's a prerequisite for this change.
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Repeated execution of an uncorrelated ARRAY_SUBLINK sub-select (which
I think can only happen if the sub-select is embedded in a larger,
correlated subquery) would leak memory for the duration of the query,
due to not reclaiming the array generated in the previous execution.
Per bug #6698 from Armando Miraglia. Diagnosis and fix idea by Heikki,
patch itself by me.
This has been like this all along, so back-patch to all supported versions.
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commit-fest.
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In lazy_scan_heap, we could issue bogus warnings about incorrect
information in the visibility map, because we checked the visibility
map bit before locking the heap page, creating a race condition. Fix
by rechecking the visibility map bit before we complain. Rejigger
some related logic so that we rely on the possibly-outdated
all_visible_according_to_vm value as little as possible.
In heap_multi_insert, it's not safe to clear the visibility map bit
before beginning the critical section. The visibility map is not
crash-safe unless we treat clearing the bit as a critical operation.
Specifically, if the transaction were to error out after we set the
bit and before entering the critical section, we could end up writing
the heap page to disk (with the bit cleared) and crashing before the
visibility map page made it to disk. That would be bad. heap_insert
has this correct, but somehow the order of operations got rearranged
when heap_multi_insert was added.
Also, add some more comments to visibilitymap_test, lazy_scan_heap,
and IndexOnlyNext, expounding on concurrency issues.
Per extensive code review by Andres Freund, and further review by Tom
Lane, who also made the original report about the bogus warnings.
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This seems more consistent with the pre-existing choices for names of
other statistics columns. Rename assorted internal identifiers to match.
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Josh Kupershmidt
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Currently, the only way to see the numbers this gathers is via
EXPLAIN (ANALYZE, BUFFERS), but the plan is to add visibility through
the stats collector and pg_stat_statements in subsequent patches.
Ants Aasma, reviewed by Greg Smith, with some further changes by me.
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For those variables only used when asserts are enabled, use a new
macro PG_USED_FOR_ASSERTS_ONLY, which expands to
__attribute__((unused)) when asserts are not enabled.
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Making this operation look like a utility statement seems generally a good
idea, and particularly so in light of the desire to provide command
triggers for utility statements. The original choice of representing it as
SELECT with an IntoClause appendage had metastasized into rather a lot of
places, unfortunately, so that this patch is a great deal more complicated
than one might at first expect.
In particular, keeping EXPLAIN working for SELECT INTO and CREATE TABLE AS
subcommands required restructuring some EXPLAIN-related APIs. Add-on code
that calls ExplainOnePlan or ExplainOneUtility, or uses
ExplainOneQuery_hook, will need adjustment.
Also, the cases PREPARE ... SELECT INTO and CREATE RULE ... SELECT INTO,
which formerly were accepted though undocumented, are no longer accepted.
The PREPARE case can be replaced with use of CREATE TABLE AS EXECUTE.
The CREATE RULE case doesn't seem to have much real-world use (since the
rule would work only once before failing with "table already exists"),
so we'll not bother with that one.
Both SELECT INTO and CREATE TABLE AS still return a command tag of
"SELECT nnnn". There was some discussion of returning "CREATE TABLE nnnn",
but for the moment backwards compatibility wins the day.
Andres Freund and Tom Lane
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Also expose the new counters through pg_stat_statements.
Patch by me. Review by Fujii Masao and Greg Smith.
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The hstore and json datatypes both have record-conversion functions that
pay attention to column names in the composite values they're handed.
We used to not worry about inserting correct field names into tuple
descriptors generated at runtime, but given these examples it seems
useful to do so. Observe the nicer-looking results in the regression
tests whose results changed.
catversion bump because there is a subtle change in requirements for stored
rule parsetrees: RowExprs from ROW() constructs now have to include field
names.
Andrew Dunstan and Tom Lane
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Sometimes it may be useful to get actual row counts out of EXPLAIN
(ANALYZE) without paying the cost of timing every node entry/exit.
With this patch, you can say EXPLAIN (ANALYZE, TIMING OFF) to get that.
Tomas Vondra, reviewed by Eric Theise, with minor doc changes by me.
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Matthew Draper, reviewed by Hitoshi Harada
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YAMAMOTO Takashi
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We can't just skip initializing such subplans, because the referencing CTE
node will expect to find the subplan available when it initializes. That
in turn means that ExecInitModifyTable must allow the case (which actually
it needed to do anyway, since there's no guarantee that ModifyTable is
exactly at the top of the CTE plan tree). So move the complaint about not
being allowed in EvalPlanQual mode to execution instead of initialization.
Testing turned up yet another problem, which is that we'd try to
re-initialize the result relation's index list, leading to leaks and
dangling pointers.
Per report from Phil Sorber. Back-patch to 9.1 where data-modifying CTEs
were introduced.
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Patch by me; review by Tom Lane, Jeff Davis, and Peter Geoghegan.
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In the previous coding, it was possible for a relation to be created
via CREATE TABLE, CREATE VIEW, CREATE SEQUENCE, CREATE FOREIGN TABLE,
etc. in a schema while that schema was meanwhile being concurrently
dropped. This led to a pg_class entry with an invalid relnamespace
value. The same problem could occur if a relation was moved using
ALTER .. SET SCHEMA while the target schema was being concurrently
dropped. This patch prevents both of those scenarios by locking the
schema to which the relation is being added using AccessShareLock,
which conflicts with the AccessExclusiveLock taken by DROP.
As a desirable side effect, this also prevents the use of CREATE OR
REPLACE VIEW to queue for an AccessExclusiveLock on a relation on which
you have no rights: that will now fail immediately with a permissions
error, before trying to obtain a lock.
We need similar protection for all other object types, but as everything
other than relations uses a slightly different set of code paths, I'm
leaving that for a separate commit.
Original complaint (as far as I could find) about CREATE by Nikhil
Sontakke; risk for ALTER .. SET SCHEMA pointed out by Tom Lane;
further details by Dan Farina; patch by me; review by Hitoshi Harada.
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As previously coded, the QueryDesc's dest pointer was left dangling
(pointing at an already-freed receiver object) after ExecutorEnd. It's a
bit astonishing that it took us this long to notice, and I'm not sure that
the known problem case with SQL functions is the only one. Fix it by
saving and restoring the original receiver pointer, which seems the most
bulletproof way of ensuring any related bugs are also covered.
Per bug #6379 from Paul Ramsey. Back-patch to 8.4 where the current
handling of SELECT INTO was introduced.
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When a PORTAL_ONE_SELECT query is executed, we can opportunistically
reuse the parse/plan shot for the execution phase. This cuts down the
number of snapshots per simple query from 2 to 1 for the simple
protocol, and 3 to 2 for the extended protocol. Since we are only
reusing a snapshot taken early in the processing of the same protocol
message, the change shouldn't be user-visible, except that the remote
possibility of the planning and execution snapshots being different is
eliminated.
Note that this change does not make it safe to assume that the parse/plan
snapshot will certainly be reused; that will currently only happen if
PortalStart() decides to use the PORTAL_ONE_SELECT strategy. It might
be worth trying to provide some stronger guarantees here in the future,
but for now we don't.
Patch by me; review by Dimitri Fontaine.
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This adds support for the more or less SQL-conforming USAGE privilege
on types and domains. The intent is to be able restrict which users
can create dependencies on types, which restricts the way in which
owners can alter types.
reviewed by Yeb Havinga
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Remove some dead code, conditionally declare some items or call
some code, and fix one or two declarations.
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