This commit includes various optimizations to improve the performance of
tuple deformation.
We now precalculate CompactAttribute's attcacheoff, which allows us to
remove the code from the deform routines which was setting the
attcacheoff. Setting the attcacheoff is now handled by
TupleDescFinalize(), which must be called before the TupleDesc is used for
anything. Having TupleDescFinalize() means we can store the first
attribute in the TupleDesc which does not have an offset cached. That
allows us to add a dedicated deforming loop to deform all attributes up
to the final one with an attcacheoff set, or up to the first NULL
attribute, whichever comes first.
Here we also improve tuple deformation performance of tuples with NULLs.
Previously, if the HEAP_HASNULL bit was set in the tuple's t_infomask,
deforming would, one-by-one, check each and every bit in the NULL bitmap
to see if it was zero. Now, we process the NULL bitmap 1 byte at a time
rather than 1 bit at a time to find the attnum with the first NULL. We
can now deform the tuple without checking for NULLs up to just before that
attribute.
We also record the maximum attribute number which is guaranteed to exist
in the tuple, that is, has a NOT NULL constraint and isn't an
atthasmissing attribute. When deforming only attributes prior to the
guaranteed attnum, we've no need to access the tuple's natt count. As an
additional optimization, we only count fixed-width columns when
calculating the maximum guaranteed column, as this eliminates the need to
emit code to fetch byref types in the deformation loop for guaranteed
attributes.
Some locations in the code deform tuples that have yet to go through NOT
NULL constraint validation. We're unable to perform the guaranteed
attribute optimization when that's the case. This optimization is opt-in
via the TupleTableSlot using the TTS_FLAG_OBEYS_NOT_NULL_CONSTRAINTS
flag.
This commit also adds a more efficient way of populating the isnull
array by using a bit-wise SWAR trick which performs multiplication on the
inverse of the tuple's bitmap byte and masking out all but the lower bit
of each of the boolean's byte. This results in much more optimal code
when compared to determining the NULLness via att_isnull(). 8 isnull
elements are processed at once using this method, which means we need to
round the tts_isnull array size up to the next 8 bytes. The palloc code
does this anyway, but the round-up needed to be formalized so as not to
overwrite the sentinel byte in MEMORY_CONTEXT_CHECKING builds. Doing
this also allows the NULL-checking deforming loop to more efficiently
check the isnull array, rather than doing the bit-wise processing for each
attribute that att_isnull() does.
The level of performance improvement from these changes seems to vary
depending on the CPU architecture. Apple's M chips seem particularly
fond of the changes, with some of the tested deform-heavy queries going
over twice as fast as before. With x86-64, the speedups aren't quite as
large. With tables containing only a small number of columns, the
speedups will be less.
Author: David Rowley <dgrowleyml@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: John Naylor <johncnaylorls@gmail.com>
Reviewed-by: Amit Langote <amitlangote09@gmail.com>
Reviewed-by: Zsolt Parragi <zsolt.parragi@percona.com>
Reviewed-by: Álvaro Herrera <alvherre@kurilemu.de>
Reviewed-by: Junwang Zhao <zhjwpku@gmail.com>
Discussion: https://postgr.es/m/CAApHDvpoFjaj3%2Bw_jD5uPnGazaw41A71tVJokLDJg2zfcigpMQ%40mail.gmail.com
The comment about ParallelWorkerNumbr in parallel.c says:
In parallel workers, it will be set to a value >= 0 and < the number
of workers before any user code is invoked; each parallel worker will
get a different parallel worker number.
However asserts in various places collecting instrumentation allowed
(ParallelWorkerNumber == num_workers). That would be a bug, as the value
is used as index into an array with num_workers entries.
Fixed by adjusting the asserts accordingly. Backpatch to all supported
versions.
Discussion: https://postgr.es/m/5db067a1-2cdf-4afb-a577-a04f30b69167@vondra.me
Reviewed-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Backpatch-through: 14
Instead of using comments to mark fallthrough switch cases, use the
fallthrough attribute. This will (in the future, not here) allow
supporting other compilers besides gcc. The commenting convention is
only supported by gcc, the attribute is supported by clang, and in the
fullness of time the C23 standard attribute would allow supporting
other compilers as well.
Right now, we package the attribute into a macro called
pg_fallthrough. This commit defines that macro and replaces the
existing comments with that macro invocation.
We also raise the level of the gcc -Wimplicit-fallthrough= option from
3 to 5 to enforce the use of the attribute.
Reviewed-by: Jelte Fennema-Nio <postgres@jeltef.nl>
Discussion: https://www.postgresql.org/message-id/flat/76a8efcd-925a-4eaf-bdd1-d972cd1a32ff%40eisentraut.org
The idea is to encourage more the use of these new routines across the
tree, as these offer stronger type safety guarantees than palloc().
This batch of changes includes most of the trivial changes suggested by
the author for src/backend/.
A total of 334 files are updated here. Among these files, 48 of them
have their build change slightly; these are caused by line number
changes as the new allocation formulas are simpler, shaving around 100
lines of code in total.
Similar work has been done in 0c3c5c3b06 and 31d3847a37.
Author: David Geier <geidav.pg@gmail.com>
Discussion: https://postgr.es/m/ad0748d4-3080-436e-b0bc-ac8f86a3466a@gmail.com
We've been nibbling away at removing uses of "long" for a long time,
since its width is platform-dependent. Here's one more: change the
remaining "long" fields in Plan nodes to Cardinality, since the three
surviving examples all represent group-count estimates. The upstream
planner code was converted to Cardinality some time ago; for example
the corresponding fields in Path nodes are type Cardinality, as are
the arguments of the make_foo_path functions. Downstream in the
executor, it turns out that these all feed to the table-size argument
of BuildTupleHashTable. Change that to "double" as well, and fix it
so that it safely clamps out-of-range values to the uint32 limit of
simplehash.h, as was not being done before.
Essentially, this is removing all the artificial datatype-dependent
limitations on these values from upstream processing, and applying
just one clamp at the moment where we're forced to do so by the
datatype choices of simplehash.h.
Also, remove BuildTupleHashTable's misguided attempt to enforce
work_mem/hash_mem_limit. It doesn't have enough information
(particularly not the expected tuple width) to do that accurately,
and it has no real business second-guessing the caller's choice.
For all these plan types, it's really the planner's responsibility
to not choose a hashed implementation if the hashtable is expected
to exceed hash_mem_limit. The previous patch improved the
accuracy of those estimates, and even if BuildTupleHashTable had
more information it should arrive at the same conclusions.
Reported-by: Jeff Janes <jeff.janes@gmail.com>
Author: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: David Rowley <dgrowleyml@gmail.com>
Discussion: https://postgr.es/m/CAMkU=1zia0JfW_QR8L5xA2vpa0oqVuiapm78h=WpNsHH13_9uw@mail.gmail.com
For all extant uses of TupleHashTables, execGrouping.c itself does
nothing with the "tablecxt" except to allocate new hash entries in it,
and the callers do nothing with it except to reset the whole context.
So this is an ideal use-case for a BumpContext, and the hash tables
are frequently big enough for the savings to be significant.
(Commit cc721c459 already taught nodeAgg.c this idea, but neglected
the other callers of BuildTupleHashTable.)
While at it, let's clean up some ill-advised leftovers from rebasing
TupleHashTables on simplehash.h:
* Many comments and variable names were based on the idea that the
tablecxt holds the whole TupleHashTable, whereas now it only holds the
hashed tuples (plus any caller-defined "additional storage"). Rename
to names like tuplescxt and tuplesContext, and adjust the comments.
Also adjust the memory context names to be like "<Foo> hashed tuples".
* Make ResetTupleHashTable() reset the tuplescxt rather than relying
on the caller to do so; that was fairly bizarre and seems like a
recipe for leaks. This is less efficient in the case where nodeAgg.c
uses the same tuplescxt for several different hashtables, but only
microscopically so because mcxt.c will short-circuit the extra resets
via its isReset flag. I judge the extra safety and intellectual
cleanliness well worth those few cycles.
* Remove the long-obsolete "allow_jit" check added by ac88807f9;
instead, just Assert that metacxt and tuplescxt are different.
We need that anyway for this definition of ResetTupleHashTable() to
be safe.
There is a side issue of the extent to which this change invalidates
the planner's estimates of hashtable memory consumption. However,
those estimates are already pretty bad, so improving them seems like
it can be a separate project. This change is useful to do first to
establish consistent executor behavior that the planner can expect.
A loose end not addressed here is that the "entrysize" calculation
in BuildTupleHashTable seems wrong: "sizeof(TupleHashEntryData) +
additionalsize" corresponds neither to the size of the simplehash
entries nor to the total space needed per tuple. It's questionable
why BuildTupleHashTable is second-guessing its caller's nbuckets
choice at all, since the original source of the number should have had
more information. But that all seems wrapped up with the planner's
estimation logic, so let's leave it for the planned followup patch.
Reported-by: Jeff Janes <jeff.janes@gmail.com>
Reported-by: David Rowley <dgrowleyml@gmail.com>
Author: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: David Rowley <dgrowleyml@gmail.com>
Discussion: https://postgr.es/m/CAMkU=1zia0JfW_QR8L5xA2vpa0oqVuiapm78h=WpNsHH13_9uw@mail.gmail.com
Discussion: https://postgr.es/m/2268409.1761512111@sss.pgh.pa.us
This fixes an unlikely issue when fetching GROUPING SET results from
their internally stored hash tables. It was possible in rare cases that
the hash iterator would be set up incorrectly which could result in a
crash.
This was introduced in 4d143509c, so backpatch to v18.
Many thanks to Yuri Zamyatin for reporting and helping to debug this
issue.
Bug: #19078
Reported-by: Yuri Zamyatin <yuri@yrz.am>
Author: David Rowley <dgrowleyml@gmail.com>
Reviewed-by: Jeff Davis <pgsql@j-davis.com>
Discussion: https://postgr.es/m/19078-dfd62f840a2c0766@postgresql.org
Backpatch-through: 18
All the calls replaced by this commit use 4-byte integers for their
variables used in input of my_log2(). Hence, the limit against
too-large inputs does not really apply. Thresholds are also applied, as
of:
- In nodeAgg.c, the number of partitions is limited by
HASHAGG_MAX_PARTITIONS.
- In nodeHash.c, ExecChooseHashTableSize() caps its maximum number of
buckets based on HashJoinTuple and palloc() allocation limit.
- In worker.c, the number of subxacts tracked by ApplySubXactData uses
uint32, making pg_ceil_log2_64() safe to use directly.
Several approaches have been discussed, like an integration with
thresholds in pg_bitutils.h, but it was found confusing. This uses
Dean's idea, which gives a simpler result than what I came up with to be
able to remove dynahash.h. dynahash.h will be removed in a follow-up
commit, removing some duplication with the ceil log2 routines.
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Reviewed-by: Dean Rasheed <dean.a.rasheed@gmail.com>
Discussion: https://postgr.es/m/CAEZATCUJPQD_7sC-wErak2CQGNa6bj2hY-mr8wsBki=kX7f2_A@mail.gmail.com
The macros INJECTION_POINT() and INJECTION_POINT_CACHED() are extended
with an optional argument that can be passed down to the callback
attached when an injection point is run, giving to callbacks the
possibility to manipulate a stack state given by the caller. The
existing callbacks in modules injection_points and test_aio have their
declarations adjusted based on that.
da7226993f (core AIO infrastructure) and 93bc3d75d8 (test_aio) and
been relying on a set of workarounds where a static variable called
pgaio_inj_cur_handle is used as runtime argument in the injection point
callbacks used by the AIO tests, in combination with a TRY/CATCH block
to reset the argument value. The infrastructure introduced in this
commit will be reused for the AIO tests, simplifying them.
Reviewed-by: Greg Burd <greg@burd.me>
Discussion: https://postgr.es/m/Z_y9TtnXubvYAApS@paquier.xyz
The entries aren't freed until the entire hash table is destroyed, so
use the Bump allocator to improve allocation speed, avoid wasting
space on the chunk header, and avoid wasting space due to the
power-of-two allocations.
Discussion: https://postgr.es/m/CAApHDvqv1aNB4cM36FzRwivXrEvBO_LsG_eQ3nqDXTjECaatOQ@mail.gmail.com
Reviewed-by: David Rowley
Knowing when the side-effects of an expression is the intended result
of the execution, rather than the returnvalue, is important for being
able generate more efficient JITed code. This replaces EEOP_DONE with
two new steps: EEOP_DONE_RETURN and EEOP_DONE_NO_RETURN. Expressions
which return a value should use the former step; expressions used for
their side-effects which don't return value should use the latter.
Author: Andres Freund <andres@anarazel.de>
Co-authored-by: Daniel Gustafsson <daniel@yesql.se>
Reviewed-by: Andreas Karlsson <andreas@proxel.se>
Discussion: https://postgr.es/m/415721CE-7D2E-4B74-B5D9-1950083BA03E@yesql.se
Discussion: https://postgr.es/m/20191023163849.sosqbfs5yenocez3@alap3.anarazel.de
Previously, the caller needed to allocate the memory and the
TupleHashTable would store a pointer to it. That wastes space for the
palloc overhead as well as the size of the pointer itself.
Now, the TupleHashTable relies on the caller to correctly specify the
additionalsize, and allocates that amount of space. The caller can
then request a pointer into that space.
Discussion: https://postgr.es/m/b9cbf0219a9859dc8d240311643ff4362fd9602c.camel@j-davis.com
Reviewed-by: Heikki Linnakangas
CHUNKHDRSZ was defined as 16 bytes, which was true when that code went in,
but since c6e0fe1f2, 8 is a more accurate value. Here we adjust it to use
sizeof(MemoryChunk), which is normally 8, or 16 for cassert builds.
c6e0fe1f2 first appeared in v16, so this is technically wrong in v16 up
to master, but let's apply this only to master as adjusting this does
influence the estimated number of batches in the aggregate costing code
and we don't want to cause plan instability in released versions.
Reviewed-by: Tom Lane
Discussion: https://postgr.es/m/CAApHDvpMpRQvsTqZo3FinXkgytwxwF8sCyZm83xDj-1s_hLe+w@mail.gmail.com
It was reasonable to preserve the old API of BuildTupleHashTable()
in the back branches, but in HEAD we should actively discourage use
of that version. There are no remaining callers in core, so just
get rid of it. Then rename BuildTupleHashTableExt() back to
BuildTupleHashTable().
While at it, fix up the miserably-poorly-maintained header comment
for BuildTupleHashTable[Ext]. It looks like more than one patch in
this area has had the opinion that updating comments is beneath them.
Discussion: https://postgr.es/m/538343.1734646986@sss.pgh.pa.us
0f5738202 adjusted the execGrouping.c code so it made use of ExprStates to
generate hash values. That commit made a wrong assumption that the slot
type to pass to ExecBuildHash32FromAttrs() is always &TTSOpsMinimalTuple.
That's not the case as the slot type depends on the slot type passed to
LookupTupleHashEntry(), which for nodeRecursiveunion.c, could be any of
the current slot types.
Here we fix this by adding a new parameter to BuildTupleHashTableExt()
to allow the slot type to be passed in. In the case of nodeSubplan.c
and nodeAgg.c the slot type is always &TTSOpsVirtual, so for both of
those cases, it's beneficial to pass the known slot type as that allows
ExecBuildHash32FromAttrs() to skip adding the tuple deform step to the
resulting ExprState. Another possible fix would have been to have
ExecBuildHash32FromAttrs() set "fetch.kind" to NULL so that
ExecComputeSlotInfo() always determines the EEOP_INNER_FETCHSOME is
required, however, that option isn't favorable as slows down aggregation
and hashed subplan evaluation due to the extra (needless) deform step.
Thanks to Nathan Bossart for bisecting to find the offending commit
based on Paul's report.
Reported-by: Paul Ramsey <pramsey@cleverelephant.ca>
Discussion: https://postgr.es/m/99F064C1-B3EB-4BE7-97D2-D2A0AA487A71@cleverelephant.ca
as determined by include-what-you-use (IWYU)
While IWYU also suggests to *add* a bunch of #include's (which is its
main purpose), this patch does not do that. In some cases, a more
specific #include replaces another less specific one.
Some manual adjustments of the automatic result:
- IWYU currently doesn't know about includes that provide global
variable declarations (like -Wmissing-variable-declarations), so
those includes are being kept manually.
- All includes for port(ability) headers are being kept for now, to
play it safe.
- No changes of catalog/pg_foo.h to catalog/pg_foo_d.h, to keep the
patch from exploding in size.
Note that this patch touches just *.c files, so nothing declared in
header files changes in hidden ways.
As a small example, in src/backend/access/transam/rmgr.c, some IWYU
pragma annotations are added to handle a special case there.
Discussion: https://www.postgresql.org/message-id/flat/af837490-6b2f-46df-ba05-37ea6a6653fc%40eisentraut.org
This commit removes unnecessary ExecExprFreeContext() calls in
ExecEnd* routines because the actual cleanup is managed by
FreeExecutorState(). With no callers remaining for
ExecExprFreeContext(), this commit also removes the function.
This commit also drops redundant ExecClearTuple() calls, because
ExecResetTupleTable() in ExecEndPlan() already takes care of
resetting and dropping all TupleTableSlots initialized with
ExecInitScanTupleSlot() and ExecInitExtraTupleSlot().
After these modifications, the ExecEnd*() routines for ValuesScan,
NamedTuplestoreScan, and WorkTableScan became redundant. So, this
commit removes them.
Reviewed-by: Robert Haas
Discussion: https://postgr.es/m/CA+HiwqFGkMSge6TgC9KQzde0ohpAycLQuV7ooitEEpbKB0O_mg@mail.gmail.com
Run pgindent, pgperltidy, and reformat-dat-files.
This set of diffs is a bit larger than typical. We've updated to
pg_bsd_indent 2.1.2, which properly indents variable declarations that
have multi-line initialization expressions (the continuation lines are
now indented one tab stop). We've also updated to perltidy version
20230309 and changed some of its settings, which reduces its desire to
add whitespace to lines to make assignments etc. line up. Going
forward, that should make for fewer random-seeming changes to existing
code.
Discussion: https://postgr.es/m/20230428092545.qfb3y5wcu4cm75ur@alvherre.pgsql
The problem that these messages protect against can only occur because
a corrupted hash spill file was written, i.e., a Postgres bug. There's
no reason to have them as translatable.
Backpatch to 15, where these messages were changed by commit c4649cce39.
Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
Discussion: https://postgr.es/m/20230510175407.dwa5v477pw62ikyx@alvherre.pgsql
The name of this function suggests that it ought to reparent R/W
expanded objects to be children of the persistent aggcontext, instead
of copying them. In fact it does no such thing, and if you try to
make it do so you will see multiple regression failures. Rename it
to the less-misleading ExecAggCopyTransValue, and add commentary
about why that attractive-sounding optimization won't work. Also
adjust comments at call sites, some of which were describing logic
that has since been moved into ExecAggCopyTransValue.
Discussion: https://postgr.es/m/3004282.1681930251@sss.pgh.pa.us
The finalfunc might return a read-write expanded object. If we
de-duplicate multiple call sites for the aggregate, any function(s)
receiving the aggregate result earlier could alter or destroy the
value that reaches the ones called later. This is a brown-paper-bag
bug in commit 42b746d4c, because we actually considered the need
for read-only-ness but failed to realize that it applied to the case
with a finalfunc as well as the case without.
Per report from Justin Pryzby. New error in HEAD,
no need for back-patch.
Discussion: https://postgr.es/m/ZDm5TuKsh3tzoEjz@telsasoft.com
nodeAppend.c used non-nullness of appendstate->as_valid_subplans as
a state flag to indicate whether it'd done ExecFindMatchingSubPlans
(or some sufficient approximation to that). This was pretty
questionable even in the beginning, since it wouldn't really work
right if there are no valid subplans. It got more questionable
after commit 27e1f1456 added logic that could reduce as_valid_subplans
to an empty set: at that point we were depending on unspecified
behavior of bms_del_members, namely that it'd not return an empty
set as NULL. It's about to start doing that, which breaks this
logic entirely. Hence, add a separate boolean flag to signal
whether as_valid_subplans has been computed.
Also fix a previously-cosmetic bug in nodeAgg.c, wherein it ignored
the return value of bms_del_member instead of updating its pointer.
Patch by me; thanks to Nathan Bossart and Richard Guo for review.
Discussion: https://postgr.es/m/1159933.1677621588@sss.pgh.pa.us
This function has been semi-deprecated ever since we invented
bms_next_member(). Its habit of scribbling on the input bitmapset
isn't great, plus for sufficiently large bitmapsets it would take
O(N^2) time to complete a loop. Now we have the additional problem
that reducing the input to empty while leaving it still accessible
would violate a planned invariant. So let's just get rid of it,
after updating the few extant callers to use bms_next_member().
Patch by me; thanks to Nathan Bossart and Richard Guo for review.
Discussion: https://postgr.es/m/1159933.1677621588@sss.pgh.pa.us
Avoid explicitly grouping by columns that we know are redundant
for sorting, for example we need group by only one of x and y in
SELECT ... WHERE x = y GROUP BY x, y
This comes up more often than you might think, as shown by the
changes in the regression tests. It's nearly free to detect too,
since we are just piggybacking on the existing logic that detects
redundant pathkeys. (In some of the existing plans that change,
it's visible that a sort step preceding the grouping step already
didn't bother to sort by the redundant column, making the old plan
a bit silly-looking.)
To do this, build processed_groupClause and processed_distinctClause
lists that omit any provably-redundant sort items, and consult those
not the originals where relevant. This means that within the
planner, one should usually consult root->processed_groupClause or
root->processed_distinctClause if one wants to know which columns
are to be grouped on; but to check whether grouping or distinct-ing
is happening at all, check non-NIL-ness of parse->groupClause or
parse->distinctClause. This is comparable to longstanding rules
about handling the HAVING clause, so I don't think it'll be a huge
maintenance problem.
nodeAgg.c also needs minor mods, because it's now possible to generate
AGG_PLAIN and AGG_SORTED Agg nodes with zero grouping columns.
Patch by me; thanks to Richard Guo and David Rowley for review.
Discussion: https://postgr.es/m/185315.1672179489@sss.pgh.pa.us
When considering an empty grouping set, we fetched
phasedata->eqfunctions[-1]. Because the eqfunctions array is
palloc'd, that would always be an aset pointer in released versions,
and thus the code accidentally failed to malfunction (since it would
do nothing unless it found a null pointer). Nonetheless this seems
like trouble waiting to happen, so add a check for length == 0.
It's depressing that our valgrind testing did not catch this.
Maybe we should reconsider the choice to not mark that word NOACCESS?
Richard Guo
Discussion: https://postgr.es/m/CAMbWs4-vZuuPOZsKOYnSAaPYGKhmacxhki+vpOKk0O7rymccXQ@mail.gmail.com
Instead of dozens of mostly-duplicate pg_foo_aclcheck() functions,
write one common function object_aclcheck() that can handle almost all
of them. We already have all the information we need, such as which
system catalog corresponds to which catalog table and which column is
the ACL column.
There are a few pg_foo_aclcheck() that don't work via the generic
function and have special APIs, so those stay as is.
I also changed most pg_foo_aclmask() functions to static functions,
since they are not used outside of aclchk.c.
Reviewed-by: Corey Huinker <corey.huinker@gmail.com>
Reviewed-by: Antonin Houska <ah@cybertec.at>
Discussion: https://www.postgresql.org/message-id/flat/95c30f96-4060-2f48-98b5-a4392d3b6066@enterprisedb.com
Here we add a new 'copy' parameter to tuplesort_getdatum so that we can
instruct the function not to datumCopy() byref Datums before returning.
Similar to 91e9e89dc, this can provide significant performance
improvements in nodeSort when sorting by a single byref column and the
sort's targetlist contains only that column.
This allows us to re-enable Datum sorts for byref types which was disabled
in 3a5817695 due to a reported memory leak.
Additionally, here we slightly optimize DISTINCT aggregates so that we no
longer perform any datumCopy() when we find the current value not to be
distinct from the previous value. Previously the code would always take a
copy of the most recent Datum and pfree the previous value, even when the
values were the same. Testing shows a small but noticeable performance
increase when aggregate transitions are skipped due to the current
transition value being the same as the prior one.
Author: David Rowley
Discussion: https://postgr.es/m/CAApHDvqS6wC5U==k9Hd26E4EQXH3QR67-T4=Q1rQ36NGvjfVSg@mail.gmail.com
Discussion: https://postgr.es/m/CAApHDvqHonfe9G1cVaKeHbDx70R_zCrM3qP2AGXpGrieSKGnhA@mail.gmail.com
MemoryContextContains is no longer reliable in the wake of c6e0fe1f2,
so we need to get rid of these uses.
It appears that there's no really good reason to force the result of
an aggregate's finalfn or serialfn to be allocated in the per-tuple
context. The only other plausible case is that the result points to
or into the aggregate's transition value, and that's fine because it
will last as long as we need it to. (This conclusion depends on the
assumption that finalfns are not allowed to scribble on the transition
value, but we've long required that.) So we can just drop the
MemoryContextContains plus datumCopy business, although we do need
to take care to not return a read-write pointer when the transition
value is an expanded datum.
Likewise, we don't really need to force the result of a window
function to be in the output context. In this case, the plausible
alternative is that it's pointing into the temporary tuple slot used
by WinGetFuncArgInPartition or WinGetFuncArgInFrame (since those
functions could return such a pointer, which might become the window
function's result). That will hold still for long enough, unless
there is another window function using the same WindowObject.
I'm content to always perform a datumCopy when there's more than one
such function.
On net, these changes should provide small speed improvements as well
as removing problematic code.
Tom Lane and David Rowley
Discussion: https://postgr.es/m/1913788.1664898906@sss.pgh.pa.us
In a similar effort to f01592f91, here we mostly rename shadowed local
variables to remove the warnings produced when compiling with
-Wshadow=compatible-local.
This fixes 63 warnings and leaves just 5.
Author: Justin Pryzby, David Rowley
Reviewed-by: Justin Pryzby
Discussion https://postgr.es/m/20220817145434.GC26426%40telsasoft.com
Make sure that function declarations use names that exactly match the
corresponding names from function definitions in storage, catalog,
access method, executor, and logical replication code, as well as in
miscellaneous utility/library code.
Like other recent commits that cleaned up function parameter names, this
commit was written with help from clang-tidy. Later commits will do the
same for other parts of the codebase.
Author: Peter Geoghegan <pg@bowt.ie>
Reviewed-By: David Rowley <dgrowleyml@gmail.com>
Discussion: https://postgr.es/m/CAH2-WznJt9CMM9KJTMjJh_zbL5hD9oX44qdJ4aqZtjFi-zA3Tg@mail.gmail.com
In a similar effort to f01592f91, here we're targetting fixing the
warnings that -Wshadow=compatible-local produces that we can fix by moving
a variable to an inner scope to stop that variable from being shadowed by
another variable declared somewhere later in the function.
All of the warnings being fixed here are changing the scope of variables
which are being used as an iterator for a "for" loop. In each instance,
the fix happens to be changing the for loop to use the C99 type
initialization. Much of this code likely pre-dates our use of C99.
Reducing the scope of the outer scoped variable seems like the safest way
to fix these. Renaming seems more likely to risk patches using the wrong
variable. Reducing the scope is more likely to result in a compilation
failure after applying some future patch rather than introducing bugs with
it.
By my count, this takes the warning count from 129 down to 114.
Author: Justin Pryzby
Discussion: https://postgr.es/m/CAApHDvrwLGBP%2BYw9vriayyf%3DXR4uPWP5jr6cQhP9au_kaDUhbA%40mail.gmail.com
ORDER BY / DISTINCT aggreagtes have, since implemented in Postgres, been
executed by always performing a sort in nodeAgg.c to sort the tuples in
the current group into the correct order before calling the transition
function on the sorted tuples. This was not great as often there might be
an index that could have provided pre-sorted input and allowed the
transition functions to be called as the rows come in, rather than having
to store them in a tuplestore in order to sort them once all the tuples
for the group have arrived.
Here we change the planner so it requests a path with a sort order which
supports the most amount of ORDER BY / DISTINCT aggregate functions and
add new code to the executor to allow it to support the processing of
ORDER BY / DISTINCT aggregates where the tuples are already sorted in the
correct order.
Since there can be many ORDER BY / DISTINCT aggregates in any given query
level, it's very possible that we can't find an order that suits all of
these aggregates. The sort order that the planner chooses is simply the
one that suits the most aggregate functions. We take the most strictly
sorted variation of each order and see how many aggregate functions can
use that, then we try again with the order of the remaining aggregates to
see if another order would suit more aggregate functions. For example:
SELECT agg(a ORDER BY a),agg2(a ORDER BY a,b) ...
would request the sort order to be {a, b} because {a} is a subset of the
sort order of {a,b}, but;
SELECT agg(a ORDER BY a),agg2(a ORDER BY c) ...
would just pick a plan ordered by {a} (we give precedence to aggregates
which are earlier in the targetlist).
SELECT agg(a ORDER BY a),agg2(a ORDER BY b),agg3(a ORDER BY b) ...
would choose to order by {b} since two aggregates suit that vs just one
that requires input ordered by {a}.
Author: David Rowley
Reviewed-by: Ronan Dunklau, James Coleman, Ranier Vilela, Richard Guo, Tom Lane
Discussion: https://postgr.es/m/CAApHDvpHzfo92%3DR4W0%2BxVua3BUYCKMckWAmo-2t_KiXN-wYH%3Dw%40mail.gmail.com
The general convention in the executor is to refer to child plans
and planstates via the outerPlan[State] and innerPlan[State]
macros, but a few places didn't do it like that. For consistency
and readability, convert all the stragglers to use the macros.
(See also commit 40f42d2a3, which did some similar cleanup a few
years ago, but missed these cases.)
Richard Guo
Discussion: https://postgr.es/m/CAMbWs4-vYhh1xsa_veah4PUed2Xq=Ed_YH3=Mqt5A3Y=EgfCEg@mail.gmail.com
This replaces the bool flag for randomAccess. An upcoming patch requires
adding another option, so instead of breaking the API for that, then
breaking it again one day if we add more options, let's just break it
once. Any boolean options we add in the future will just make use of an
unused bit in the flags.
Any extensions making use of tuplesorts will need to update their code
to pass TUPLESORT_RANDOMACCESS instead of true for randomAccess.
TUPLESORT_NONE can be used for a set of empty options.
Author: David Rowley
Reviewed-by: Justin Pryzby
Discussion: https://postgr.es/m/CAApHDvoH4ASzsAOyHcxkuY01Qf%2B%2B8JJ0paw%2B03dk%2BW25tQEcNQ%40mail.gmail.com
