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Despite the best efforts of commit 0e5c82380, we're still seeing
occasional failures of postgres_fdw's query_cancel test in the
buildfarm. Investigation suggests that its 100ms timeout is
still not enough to reliably ensure that the remote side starts
the query before receiving the cancel request --- and if it
hasn't, it will just discard the request because it's idle.
We discussed allowing a cancel request to kill the next-received
query, but that would have wide and perhaps unpleasant side-effects.
What seems safer is to make postgres_fdw do what a human user would
likely do, which is issue another cancel request if the first one
didn't seem to do anything. We'll keep the same overall 30 second
grace period before concluding things are broken, but issue additional
cancel requests after 1 second, then 2 more seconds, then 4, then 8.
(The next one in series is 16 seconds, but we'll hit the 30 second
timeout before that.)
Having done that, revert the timeout in query_cancel.sql to 10 ms.
That will still be enough on most machines, most of the time, for
the remote query to start; but now we're intentionally risking the
race condition occurring sometimes in the buildfarm, so that the
repeat-cancel code path will get some testing.
As before, back-patch to v17. We might eventually contemplate
back-patching this further, and/or adding similar logic to dblink.
But given the lack of field complaints to date, this feels like
mostly an exercise in test case stabilization, so v17 is enough.
Discussion: https://postgr.es/m/colnv3lzzmc53iu5qoawynr6qq7etn47lmggqr65ddtpjliq5d@glkveb4m6nop
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The new compact_attrs array stores a few select fields from
FormData_pg_attribute in a more compact way, using only 16 bytes per
column instead of the 104 bytes that FormData_pg_attribute uses. Using
CompactAttribute allows performance-critical operations such as tuple
deformation to be performed without looking at the FormData_pg_attribute
element in TupleDesc which means fewer cacheline accesses.
For some workloads, tuple deformation can be the most CPU intensive part
of processing the query. Some testing with 16 columns on a table
where the first column is variable length showed around a 10% increase in
transactions per second for an OLAP type query performing aggregation on
the 16th column. However, in certain cases, the increases were much
higher, up to ~25% on one AMD Zen4 machine.
This also makes pg_attribute.attcacheoff redundant. A follow-on commit
will remove it, thus shrinking the FormData_pg_attribute struct by 4
bytes.
Author: David Rowley
Reviewed-by: Andres Freund, Victor Yegorov
Discussion: https://postgr.es/m/CAApHDvrBztXP3yx=NKNmo3xwFAFhEdyPnvrDg3=M0RhDs+4vYw@mail.gmail.com
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The topic of turning EXPLAIN's BUFFERS option on with the ANALYZE option
has come up a few times over the past few years. In many ways, doing this
seems like a good idea as it may be more obvious to users why a given
query is running more slowly than they might expect. Also, from my own
(David's) personal experience, I've seen users posting to the mailing
lists with two identical plans, one slow and one fast asking why their
query is sometimes slow. In many cases, this is due to additional reads.
Having BUFFERS on by default may help reduce some of these questions, and
if not, make it more obvious to the user before they post, or save a
round-trip to the mailing list when additional I/O effort is the cause of
the slowness.
The general consensus is that we want BUFFERS on by default with
ANALYZE. However, there were more than zero concerns raised with doing
so. The primary reason against is the additional verbosity, making it
harder to read large plans. Another concern was that buffer information
isn't always useful so may not make sense to have it on by default.
It's currently December, so let's commit this to see if anyone comes
forward with a strong objection against making this change. We have over
half a year remaining in the v18 cycle where we could still easily consider
reverting this if someone were to come forward with a convincing enough
reason as to why doing this is a bad idea.
There were two patches independently submitted to achieve this goal, one
by me and the other by Guillaume. This commit is a mix of both of these
patches with some additional work done by me to adjust various
additional places in the documentation which include EXPLAIN ANALYZE
output.
Author: Guillaume Lelarge, David Rowley
Reviewed-by: Robert Haas, Greg Sabino Mullane, Michael Christofides
Discussion: https://postgr.es/m/CANNMO++W7MM8T0KyXN3ZheXXt-uLVM3aEtZd+WNfZ=obxffUiA@mail.gmail.com
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Many of them just seem to have been copied around for no real reason.
Their presence causes (small) risks of hiding actual type mismatches
or silently discarding qualifiers
Discussion: https://www.postgresql.org/message-id/flat/461ea37c-8b58-43b4-9736-52884e862820@eisentraut.org
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Like INT64_FORMAT and UINT64_FORMAT, these macros produce format
strings for 64-bit integers. However, INT64_HEX_FORMAT and
UINT64_HEX_FORMAT generate the output in hexadecimal instead of
decimal. Besides introducing these macros, this commit makes use
of them in several places. This was originally intended to be part
of commit 5d6187d2a2, but I left it out because I felt there was a
nonzero chance that back-patching these new macros into c.h could
cause problems with third-party code. We tend to be less cautious
with such changes in new major versions.
Note that UINT64_HEX_FORMAT was originally added in commit
ee1b30f128, but it was placed in test_radixtree.c, so it wasn't
widely available. This commit moves UINT64_HEX_FORMAT to c.h.
Discussion: https://postgr.es/m/ZwQvtUbPKaaRQezd%40nathan
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as determined by IWYU
Similar to commit dbbca2cf299, but for contrib, pl, and src/test/.
Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://www.postgresql.org/message-id/flat/0df1d5b1-8ca8-4f84-93be-121081bde049%40eisentraut.org
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Several places treat MyStartTime as a "long", which is only 32 bits
wide on some platforms. In reality, MyStartTime is a pg_time_t,
i.e., a signed 64-bit integer. This will lead to interesting bugs
on the aforementioned systems in 2038 when signed 32-bit integers
are no longer sufficient to store Unix time (e.g., "pg_ctl start"
hanging). To fix, ensure that MyStartTime is handled as a 64-bit
value everywhere. (Of course, users will need to ensure that
time_t is 64 bits wide on their system, too.)
Co-authored-by: Max Johnson
Discussion: https://postgr.es/m/CO1PR07MB905262E8AC270FAAACED66008D682%40CO1PR07MB9052.namprd07.prod.outlook.com
Backpatch-through: 12
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This commit adds a "user_name" output column to
the postgres_fdw_get_connections function, returning the name
of the local user mapped to the foreign server for each connection.
If a public mapping is used, it returns "public."
This helps identify postgres_fdw connections more easily,
such as determining which connections are invalid, closed,
or used within the current transaction.
No extension version bump is needed, as commit c297a47c5f
already handled it for v18~.
Author: Hayato Kuroda
Reviewed-by: Fujii Masao
Discussion: https://postgr.es/m/b492a935-6c7e-8c08-e485-3c1d64d7d10f@oss.nttdata.com
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This test occasionally shows
+WARNING: could not get result of cancel request due to timeout
which appears to be because the cancel request is sometimes unluckily
sent to the remote session between queries, and then it's ignored.
This patch tries to make that less probable in three ways:
1. Use a test query that does not involve remote estimates, so that
no EXPLAINs are sent.
2. Make sure that the remote session is ready-to-go (transaction
started, SET commands sent) before we start the timer.
3. Increase the statement_timeout to 100ms, to give the local
session enough time to plan and issue the query.
We might have to go higher than 100ms to make this adequately
stable in the buildfarm, but let's see how it goes.
Back-patch to v17 where this test was introduced.
Jelte Fennema-Nio and Tom Lane
Discussion: https://postgr.es/m/578934.1725045685@sss.pgh.pa.us
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Previously, when a path type was disabled by e.g. enable_seqscan=false,
we either avoided generating that path type in the first place, or
more commonly, we added a large constant, called disable_cost, to the
estimated startup cost of that path. This latter approach can distort
planning. For instance, an extremely expensive non-disabled path
could seem to be worse than a disabled path, especially if the full
cost of that path node need not be paid (e.g. due to a Limit).
Or, as in the regression test whose expected output changes with this
commit, the addition of disable_cost can make two paths that would
normally be distinguishible in cost seem to have fuzzily the same cost.
To fix that, we now count the number of disabled path nodes and
consider that a high-order component of both the startup cost and the
total cost. Hence, the path list is now sorted by disabled_nodes and
then by total_cost, instead of just by the latter, and likewise for
the partial path list. It is important that this number is a count
and not simply a Boolean; else, as soon as we're unable to respect
disabled path types in all portions of the path, we stop trying to
avoid them where we can.
Because the path list is now sorted by the number of disabled nodes,
the join prechecks must compute the count of disabled nodes during
the initial cost phase instead of postponing it to final cost time.
Counts of disabled nodes do not cross subquery levels; at present,
there is no reason for them to do so, since the we do not postpone
path selection across subquery boundaries (see make_subplan).
Reviewed by Andres Freund, Heikki Linnakangas, and David Rowley.
Discussion: http://postgr.es/m/CA+TgmoZ_+MS+o6NeGK2xyBv-xM+w1AfFVuHE4f_aq6ekHv7YSQ@mail.gmail.com
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When pg_dump retrieves the list of database objects and performs the
data dump, there was possibility that objects are replaced with others
of the same name, such as views, and access them. This vulnerability
could result in code execution with superuser privileges during the
pg_dump process.
This issue can arise when dumping data of sequences, foreign
tables (only 13 or later), or tables registered with a WHERE clause in
the extension configuration table.
To address this, pg_dump now utilizes the newly introduced
restrict_nonsystem_relation_kind GUC parameter to restrict the
accesses to non-system views and foreign tables during the dump
process. This new GUC parameter is added to back branches too, but
these changes do not require cluster recreation.
Back-patch to all supported branches.
Reviewed-by: Noah Misch
Security: CVE-2024-7348
Backpatch-through: 12
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The buildfarm member "hake" reported a failure in the regression test
added by commit 857df3cef7, where postgres_fdw_get_connections(true)
returned unexpected results.
The function postgres_fdw_get_connections(true) checks
if a connection is closed by using POLLRDHUP in the requested events
and calling poll(). Previously, the function only considered
POLLRDHUP or 0 as valid returned events. However, poll() can also
return POLLHUP, POLLERR, and/or POLLNVAL. So if any of these events
were returned, postgres_fdw_get_connections(true) would report
incorrect results. postgres_fdw_get_connections(true) failed to
account for these return events.
This commit updates postgres_fdw_get_connections(true) to correctly
report a closed connection when poll() returns not only POLLRDHUP
but also POLLHUP, POLLERR, or POLLNVAL.
Discussion: https://postgr.es/m/fd8f6186-9e1e-4b9a-92c5-e71e3697d381@oss.nttdata.com
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This commit extends the postgres_fdw_get_connections() function
to check if connections are closed. This is useful for detecting closed
postgres_fdw connections that could prevent successful transaction
commits. Users can roll back transactions immediately upon detecting
closed connections, avoiding unnecessary processing of failed
transactions.
This feature is available only on systems supporting the non-standard
POLLRDHUP extension to the poll system call, including Linux.
Author: Hayato Kuroda
Reviewed-by: Shinya Kato, Zhihong Yu, Kyotaro Horiguchi, Andres Freund
Reviewed-by: Onder Kalaci, Takamichi Osumi, Vignesh C, Tom Lane, Ted Yu
Reviewed-by: Katsuragi Yuta, Peter Smith, Shubham Khanna, Fujii Masao
Discussion: https://postgr.es/m/TYAPR01MB58662809E678253B90E82CE5F5889@TYAPR01MB5866.jpnprd01.prod.outlook.com
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This commit extends the postgres_fdw_get_connections() function to
include a new used_in_xact column, indicating whether each connection
is used in the current transaction.
This addition is particularly useful for the upcoming feature that
will check if connections are closed. By using those information,
users can verify if postgres_fdw connections used in a transaction
remain open. If any connection is closed, the transaction cannot
be committed successfully. In this case users can roll back it
immediately without waiting for transaction end.
The SQL API for postgres_fdw_get_connections() is updated by
this commit and may change in the future. To handle compatibility
with older SQL declarations, an API versioning system is introduced,
allowing the function to behave differently based on the API version.
Author: Hayato Kuroda
Reviewed-by: Fujii Masao
Discussion: https://postgr.es/m/be9382f7-5072-4760-8b3f-31d6dffa8d62@oss.nttdata.com
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This allows us to skip it in Cygwin, where it's reportedly flaky because
of platform bugs or something.
Backpatch to 17, where the test was introduced by commit 2466d6654f85.
Reported-by: Alexander Lakhin <exclusion@gmail.com>
Discussion: https://postgr.es/m/e4d0cb33-6be5-e4d5-ae49-9eac3ff2b005@gmail.com
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Commit d844cd75a disallowed rewind in a non-scrollable cursor to resolve
anomalies arising from such a cursor operation. However, this failed to
take into account the assumption in postgres_fdw that when rescanning a
foreign relation, it can rewind the cursor created for scanning the
foreign relation without specifying the SCROLL option, regardless of its
scrollability, causing this error when it tried to do such a rewind in a
non-scrollable cursor. Fix by modifying postgres_fdw to instead
recreate the cursor, regardless of its scrollability, when rescanning
the foreign relation. (If we had a way to check its scrollability, we
could improve this by rewinding it if it is scrollable and recreating it
if not, but we do not have it, so this commit modifies it to recreate it
in any case.)
Per bug #17889 from Eric Cyr. Devrim Gunduz also reported this problem.
Back-patch to v15 where that commit enforced the prohibition.
Reviewed by Tom Lane.
Discussion: https://postgr.es/m/17889-e8c39a251d258dda%40postgresql.org
Discussion: https://postgr.es/m/b415ac3255f8352d1ea921cf3b7ba39e0587768a.camel%40gunduz.org
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If we intend to generate a Memoize node on top of a path, we need
cache keys of some sort. Currently we search for the cache keys in
the parameterized clauses of the path as well as the lateral_vars of
its parent. However, it turns out that this is not sufficient because
there might be lateral references derived from PlaceHolderVars, which
we fail to take into consideration.
This oversight can cause us to miss opportunities to utilize the
Memoize node. Moreover, in some plans, failing to recognize all the
cache keys could result in performance regressions. This is because
without identifying all the cache keys, we would need to purge the
entire cache every time we get a new outer tuple during execution.
This patch fixes this issue by extracting lateral Vars from within
PlaceHolderVars and subsequently including them in the cache keys.
In passing, this patch also includes a comment clarifying that Memoize
nodes are currently not added on top of join relation paths. This
explains why this patch only considers PlaceHolderVars that are due to
be evaluated at baserels.
Author: Richard Guo
Reviewed-by: Tom Lane, David Rowley, Andrei Lepikhov
Discussion: https://postgr.es/m/CAMbWs48jLxn0pAPZpJ50EThZ569Xrw+=4Ac3QvkpQvNszbeoNg@mail.gmail.com
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Hash joins can support semijoin with the LHS input on the right, using
the existing logic for inner join, combined with the assurance that only
the first match for each inner tuple is considered, which can be
achieved by leveraging the HEAP_TUPLE_HAS_MATCH flag. This can be very
useful in some cases since we may now have the option to hash the
smaller table instead of the larger.
Merge join could likely support "Right Semi Join" too. However, the
benefit of swapping inputs tends to be small here, so we do not address
that in this patch.
Note that this patch also modifies a test query in join.sql to ensure it
continues testing as intended. With this patch the original query would
result in a right-semi-join rather than semi-join, compromising its
original purpose of testing the fix for neqjoinsel's behavior for
semi-joins.
Author: Richard Guo
Reviewed-by: wenhui qiu, Alena Rybakina, Japin Li
Discussion: https://postgr.es/m/CAMbWs4_X1mN=ic+SxcyymUqFx9bB8pqSLTGJ-F=MHy4PW3eRXw@mail.gmail.com
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Previously, when considering LIMIT pushdown, postgres_fdw failed to
check whether the query has this clause, which led to pushing false
LIMIT clauses, causing incorrect results.
This clause has been supported since v13, so we need to do a
remote-version check before deciding that it will be safe to push such a
clause, but we do not currently have a way to do the check (without
accessing the remote server); disable pushing such a clause for now.
Oversight in commit 357889eb1. Back-patch to v13, where that commit
added the support.
Per bug #18467 from Onder Kalaci.
Patch by Japin Li, per a suggestion from Tom Lane, with some changes to
the comments by me. Review by Onder Kalaci, Alvaro Herrera, and me.
Discussion: https://postgr.es/m/18467-7bb89084ff03a08d%40postgresql.org
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This reverts commit 7204f35919b7e021e8d1bc9f2d76fd6bfcdd2070,
thus restoring 66c0185a3 (Allow planner to use Merge Append to
efficiently implement UNION) as well as the follow-on commits
d5d2205c8, 3b1a7eb28, 7487044d6.
Per further discussion on pgsql-release, we wish to ship beta1 with
this feature, and patch the bug that was found just before wrap,
rather than shipping beta1 with the feature reverted.
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This reverts 66c0185a3 (Allow planner to use Merge Append to
efficiently implement UNION) as well as the follow-on commits
d5d2205c8, 3b1a7eb28, 7487044d6. In addition to those, 07746a8ef
had to be removed then re-applied in a different place, because
66c0185a3 moved the relevant code.
The reason for this last-minute thrashing is that depesz found a
case in which the patched code creates a completely wrong plan
that silently gives incorrect query results. It's unclear what
the cause is or how many cases are affected, but with beta1 wrap
staring us in the face, there's no time for closer investigation.
After we figure that out, we can decide whether to un-revert this
for beta2 or hold it for v18.
Discussion: https://postgr.es/m/Zktzf926vslR35Fv@depesz.com
(also some private discussion among pgsql-release)
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This should have the same results for all practical purposes.
The advantage of selecting 'GMT' is that it's guaranteed to work
even when the remote system's timezone database is missing
entries, because pg_tzset() hard-wires handling of that,
at least in 9.2 and later.
(It seems like it would be a good idea to similarly hard-wire
correct handling of 'UTC', but that'll be a little more invasive
than I want to consider back-patching. Leave that for another
day when we're not in feature freeze.)
Per trouble report from Adnan Dautovic. Back-patch to all
supported branches.
Discussion: https://postgr.es/m/465248.1712211585@sss.pgh.pa.us
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We updated this comment in back branches (see commit f6f61a4bd et al);
let's do so in HEAD as well for consistency.
Discussion: https://postgr.es/m/CAPmGK142V1kqDfjo2H%2Bb54JTn2woVBrisFq%2B%3D9jwXwxr0VvbgA%40mail.gmail.com
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This adjusts various appendStringInfo* function calls to use a more
appropriate and efficient function with the same behavior. For example,
use appendStringInfoChar() when appending a single character rather than
appendStringInfo() and appendStringInfoString() when no formatting is
required rather than using appendStringInfo().
All adjustments made here are in code that's new to v17, so it makes
sense to fix these now rather than wait a few years and make
backpatching harder.
Discussion: https://postgr.es/m/CAApHDvojY2UvMiO+9_55ArTj10P1LBNJyyoGB+C65BLDNT0GsQ@mail.gmail.com
Reviewed-by: Nathan Bossart, Tom Lane
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Per headerscheck's C++ check.
Discussion: https://postgr.es/m/372769.1712179784@sss.pgh.pa.us
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There is no case where we would call pgfdw_exec_cleanup_query or
pgfdw_exec_cleanup_query_{begin,end} with a NULL query string, so this
expression is pointless; remove it and instead add to the latter
functions an assertion ensuring the given query string is not NULL.
Thinko in commit 815d61fcd.
Discussion: https://postgr.es/m/CAPmGK14mm%2B%3DUjyjoWj_Hu7c%2BQqX-058RFfF%2BqOkcMZ_Nj52v-A%40mail.gmail.com
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The test fails when RESET statement_timeout takes longer than 10ms.
Avoid the problem by using SET LOCAL instead.
Overall, this test is not ideal: 10ms could be shorter than the time to
have sent the query to the "remote" server, so it's possible that on
some machines this test doesn't actually witness a remote query being
cancelled. We may want to improve on this someday by using some other
testing technique, but for now it's better than nothing. I verified
manually that one round of remote cancellation occurs when this runs on
my machine.
Discussion: https://postgr.es/m/CAGECzQRsdWnj=YaaPCnA8d7E1AdbxRPBYmyBQRMPUijR2MpM_w@mail.gmail.com
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Commit 61461a300c1c introduced new functions to libpq for cancelling
queries. This commit introduces a helper function that backend-side
libraries and extensions can use to invoke those. This function takes a
timeout and can itself be interrupted while it is waiting for a cancel
request to be sent and processed, instead of being blocked.
This replaces the usage of the old functions in postgres_fdw and dblink.
Finally, it also adds some test coverage for the cancel support in
postgres_fdw.
Author: Jelte Fennema-Nio <postgres@jeltef.nl>
Discussion: https://postgr.es/m/CAGECzQT_VgOWWENUqvUV9xQmbaCyXjtRRAYO8W07oqashk_N+g@mail.gmail.com
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Until now, UNION queries have often been suboptimal as the planner has
only ever considered using an Append node and making the results unique
by either using a Hash Aggregate, or by Sorting the entire Append result
and running it through the Unique operator. Both of these methods
always require reading all rows from the union subqueries.
Here we adjust the union planner so that it can request that each subquery
produce results in target list order so that these can be Merge Appended
together and made unique with a Unique node. This can improve performance
significantly as the union child can make use of the likes of btree
indexes and/or Merge Joins to provide the top-level UNION with presorted
input. This is especially good if the top-level UNION contains a LIMIT
node that limits the output rows to a small subset of the unioned rows as
cheap startup plans can be used.
Author: David Rowley
Reviewed-by: Richard Guo, Andy Fan
Discussion: https://postgr.es/m/CAApHDvpb_63XQodmxKUF8vb9M7CxyUyT4sWvEgqeQU-GB7QFoQ@mail.gmail.com
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Historically we've printed SubPlan expression nodes as "(SubPlan N)",
which is pretty uninformative. Trying to reproduce the original SQL
for the subquery is still as impractical as before, and would be
mighty verbose as well. However, we can still do better than that.
Displaying the "testexpr" when present, and adding a keyword to
indicate the SubLinkType, goes a long way toward showing what's
really going on.
In addition, this patch gets rid of EXPLAIN's use of "$n" to represent
subplan and initplan output Params. Instead we now print "(SubPlan
N).colX" or "(InitPlan N).colX" to represent the X'th output column
of that subplan. This eliminates confusion with the use of "$n" to
represent PARAM_EXTERN Params, and it's useful for the first part of
this change because it eliminates needing some other indication of
which subplan is referenced by a SubPlan that has a testexpr.
In passing, this adds simple regression test coverage of the
ROWCOMPARE_SUBLINK code paths, which were entirely unburdened
by testing before.
Tom Lane and Dean Rasheed, reviewed by Aleksander Alekseev.
Thanks to Chantal Keller for raising the question of whether
this area couldn't be improved.
Discussion: https://postgr.es/m/2838538.1705692747@sss.pgh.pa.us
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Similar to commit 7e735035f20.
Author: Richard Guo <guofenglinux@gmail.com>
Reviewed-by: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CAMbWs4-WhpCFMbXCjtJ%2BFzmjfPrp7Hw1pk4p%2BZpU95Kh3ofZ1A%40mail.gmail.com
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For UNION ALL queries where a union child query contained a foreign
table, if the targetlist of that query contained a constant, and the
top-level query performed an ORDER BY which contained the column for the
constant value, then postgres_fdw would find the EquivalenceMember with
the Const and then try to produce an ORDER BY containing that Const.
This caused problems with INT typed Consts as these could appear to be
requests to order by an ordinal column position rather than the constant
value. This could lead to either an error such as:
ERROR: ORDER BY position <int const> is not in select list
or worse, if the constant value is a valid column, then we could just
sort by the wrong column altogether.
Here we fix this issue by just not including these Consts in the ORDER
BY clause.
In passing, add a new section for testing ORDER BY in the postgres_fdw
tests and move two existing tests which were misplaced in the WHERE
clause testing section into it.
Reported-by: Michał Kłeczek
Reviewed-by: Ashutosh Bapat, Richard Guo
Bug: #18381
Discussion: https://postgr.es/m/0714C8B8-8D82-4ABB-9F8D-A0C3657E7B6E%40kleczek.org
Discussion: https://postgr.es/m/18381-137456acd168bf93%40postgresql.org
Backpatch-through: 12, oldest supported version
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For ANY-SUBLINK, we adopted a two-stage pull-up approach to handle
different types of scenarios. In the first stage, the sublink is pulled up
as a subquery. Because of this, when writing this code, we did not have
the ability to perform lateral joins, and therefore, we were unable to
pull up Var with varlevelsup=1. Now that we have the ability to use
lateral joins, we can eliminate this limitation.
Author: Andy Fan <zhihui.fan1213@gmail.com>
Author: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Richard Guo <guofenglinux@gmail.com>
Reviewed-by: Alena Rybakina <lena.ribackina@yandex.ru>
Reviewed-by: Andrey Lepikhov <a.lepikhov@postgrespro.ru>
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Until now PostgreSQL has not been very smart about optimizing away IS
NOT NULL base quals on columns defined as NOT NULL. The evaluation of
these needless quals adds overhead. Ordinarily, anyone who came
complaining about that would likely just have been told to not include
the qual in their query if it's not required. However, a recent bug
report indicates this might not always be possible.
Bug 17540 highlighted that when we optimize Min/Max aggregates the IS NOT
NULL qual that the planner adds to make the rewritten plan ignore NULLs
can cause issues with poor index choice. That particular case
demonstrated that other quals, especially ones where no statistics are
available to allow the planner a chance at estimating an approximate
selectivity for can result in poor index choice due to cheap startup paths
being prefered with LIMIT 1.
Here we take generic approach to fixing this by having the planner check
for NOT NULL columns and just have the planner remove these quals (when
they're not needed) for all queries, not just when optimizing Min/Max
aggregates.
Additionally, here we also detect IS NULL quals on a NOT NULL column and
transform that into a gating qual so that we don't have to perform the
scan at all. This also works for join relations when the Var is not
nullable by any outer join.
This also helps with the self-join removal work as it must replace
strict join quals with IS NOT NULL quals to ensure equivalence with the
original query.
Author: David Rowley, Richard Guo, Andy Fan
Reviewed-by: Richard Guo, David Rowley
Discussion: https://postgr.es/m/CAApHDvqg6XZDhYRPz0zgOcevSMo0d3vxA9DvHrZtKfqO30WTnw@mail.gmail.com
Discussion: https://postgr.es/m/17540-7aa1855ad5ec18b4%40postgresql.org
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This replaces dblink's blocking libpq calls, allowing cancellation and
allowing DROP DATABASE (of a database not involved in the query). Apart
from explicit dblink_cancel_query() calls, dblink still doesn't cancel
the remote side. The replacement for the blocking calls consists of
new, general-purpose query execution wrappers in the libpqsrv facility.
Out-of-tree extensions should adopt these. Use them in postgres_fdw,
replacing a local implementation from which the libpqsrv implementation
derives. This is a bug fix for dblink. Code inspection identified the
bug at least thirteen years ago, but user complaints have not appeared.
Hence, no back-patch for now.
Discussion: https://postgr.es/m/20231122012945.74@rfd.leadboat.com
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Reported-by: Michael Paquier
Discussion: https://postgr.es/m/ZZKTDPxBBMt3C0J9@paquier.xyz
Backpatch-through: 12
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Dagfinn Ilmari Mannsåker, reviewed by Shubham Khanna. Some subtractions
by me.
Discussion: http://postgr.es/m/87le9fmi01.fsf@wibble.ilmari.org
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SEMI-JOIN is deparsed as the EXISTS subquery. It references outer and inner
relations, so it should be evaluated as the condition in the upper-level WHERE
clause. The signatures of deparseFromExprForRel() and deparseRangeTblRef() are
revised so that they can add conditions to the upper level.
PgFdwRelationInfo now has a hidden_subquery_rels field, referencing the relids
used in the inner parts of semi-join. They can't be referred to from upper
relations and should be used internally for equivalence member searches.
The planner can create semi-join, which refers to inner rel vars in its target
list. However, we deparse semi-join as an exists() subquery. So we skip the
case when the target list references to inner rel of semi-join.
Author: Alexander Pyhalov
Reviewed-by: Ashutosh Bapat, Ian Lawrence Barwick, Yuuki Fujii, Tomas Vondra
Discussion: https://postgr.es/m/c9e2a757cf3ac2333714eaf83a9cc184@postgrespro.ru
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Display the name of the foreign server for which the user mapping was
not found.
Author: Ian Lawrence Barwick <barwick@gmail.com>
Reviewed-by: Laurenz Albe <laurenz.albe@cybertec.at>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Discussion: https://www.postgresql.org/message-id/flat/CAB8KJ=jFzNaeyFtLcTZNOc6fd1+F93pGVLFa-wyt31wn7VNxqQ@mail.gmail.com
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A WaitEventSet holds file descriptors or event handles (on Windows).
If FreeWaitEventSet is not called, those fds or handles are leaked.
Use ResourceOwners to track WaitEventSets, to clean those up
automatically on error.
This was a live bug in async Append nodes, if a FDW's
ForeignAsyncRequest function failed. (In back branches, I will apply a
more localized fix for that based on PG_TRY-PG_FINALLY.)
The added test doesn't check for leaking resources, so it passed even
before this commit. But at least it covers the code path.
In the passing, fix misleading comment on what the 'nevents' argument
to WaitEventSetWait means.
Report by Alexander Lakhin, analysis and suggestion for the fix by
Tom Lane. Fixes bug #17828.
Reviewed-by: Alexander Lakhin, Thomas Munro
Discussion: https://www.postgresql.org/message-id/472235.1678387869@sss.pgh.pa.us
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cac169d68 adjusted DEFAULT_FDW_TUPLE_COST and that seems to have caused
a test to become unstable on 32-bit machines.
4b14e1871 tried to fix this as originally the plan was flipping between
a Nested Loop and Hash Join. That commit forced the Nested Loop, but
there's still flexibility to push or not push the sort to the remote
server and 32-bit seems to prefer to push and on 64-bit, the costs
prefer not to.
Here let's just turn off enable_sort to significantly encourage the sort
to take place on the remote server.
Reported-by: Michael Paquier, Richard Guo
Discussion: https://postgr.es/m/ZUM2IhA8X2lrG50K@paquier.xyz
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cac169d68 adjusted DEFAULT_FDW_TUPLE_COST and that seems to have caused
a test to become unstable on 32-bit machines. Try to make it stable
again.
Reported-by: Michael Paquier
Discussion: https://postgr.es/m/ZUM2IhA8X2lrG50K@paquier.xyz
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0.01 was unrealistically low as it's the same as the default
cpu_tuple_cost and 10x cheaper than the default parallel_tuple_cost.
It's hard to imagine a situation where fetching a tuple from a foreign
server would be cheaper than fetching one from a parallel worker.
After some experimentation on a loopback server, somewhere between 0.15
and 0.3 seems more realistic. Here we split the difference and set it
to 0.2.
This will cause operations that reduce the number of tuples (e.g.
aggregation) to be more likely to take place on the foreign server.
Adjusting this causes some plan changes in the postgres_fdw regression
tests. This is because penalizing each Path with the additional tuple
costs causes some dilution of the costs of the other operations being
charged for and results in various paths appearing to be closer to the
same costs such that add_path's STD_FUZZ_FACTOR is more likely to see two
paths as costing (fuzzily) the same. This isn't ideal, but it shouldn't
be reason enough to use artificially low costs.
Discussion: https://postgr.es/m/CAApHDvopVjjfh5c1Ed2HRvDdfom2dEpMwwiu5-f1AnmYprJngA@mail.gmail.com
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Since C99, there can be a trailing comma after the last value in an
enum definition. A lot of new code has been introducing this style on
the fly. Some new patches are now taking an inconsistent approach to
this. Some add the last comma on the fly if they add a new last
value, some are trying to preserve the existing style in each place,
some are even dropping the last comma if there was one. We could
nudge this all in a consistent direction if we just add the trailing
commas everywhere once.
I omitted a few places where there was a fixed "last" value that will
always stay last. I also skipped the header files of libpq and ecpg,
in case people want to use those with older compilers. There were
also a small number of cases where the enum type wasn't used anywhere
(but the enum values were), which ended up confusing pgindent a bit,
so I left those alone.
Discussion: https://www.postgresql.org/message-id/flat/386f8c45-c8ac-4681-8add-e3b0852c1620%40eisentraut.org
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Three custom wait events are added here:
- "PostgresFdwCleanupResult", waiting while cleaning up PQgetResult() on
transaction abort.
- "PostgresFdwConnect", waiting to establish a connection to a remote
server.
- "PostgresFdwGetResult", waiting to receive a result from a remote
server.
Author: Masahiro Ikeda
Discussion: https://postgr.es/m/197bce267fa691a0ac62c86c4ab904c4@oss.nttdata.com
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Commit e4106b252 should have updated this test, but did not; back-patch
to all supported branches.
Reviewed by Richard Guo.
Discussion: http://postgr.es/m/CAPmGK15nR0NXLSCKQAcqbZbTzrzd5MozowWnTnGfPkayndF43Q%40mail.gmail.com
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Per buildfarm member koel
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quals.
This was disabled in commit 6f80a8d9c due to the lack of support for
handling of pseudoconstant quals assigned to replaced joins in
createplan.c. To re-allow it, this patch adds the support by 1)
modifying the ForeignPath and CustomPath structs so that if they
represent foreign and custom scans replacing a join with a scan, they
store the list of RestrictInfo nodes to apply to the join, as in
JoinPaths, and by 2) modifying create_scan_plan() in createplan.c so
that it uses that list in that case, instead of the baserestrictinfo
list, to get pseudoconstant quals assigned to the join, as mentioned in
the commit message for that commit.
Important item for the release notes: this is non-backwards-compatible
since it modifies the ForeignPath and CustomPath structs, as mentioned
above, and changes the argument lists for FDW helper functions
create_foreignscan_path(), create_foreign_join_path(), and
create_foreign_upper_path().
Richard Guo, with some additional changes by me, reviewed by Nishant
Sharma, Suraj Kharage, and Richard Guo.
Discussion: https://postgr.es/m/CADrsxdbcN1vejBaf8a%2BQhrZY5PXL-04mCd4GDu6qm6FigDZd6Q%40mail.gmail.com
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Commit e7cb7ee14, which introduced the infrastructure for FDWs and
custom scan providers to replace joins with scans, failed to add support
handling of pseudoconstant quals assigned to replaced joins in
createplan.c, leading to an incorrect plan without a gating Result node
when postgres_fdw replaced a join with such a qual.
To fix, we could add the support by 1) modifying the ForeignPath and
CustomPath structs to store the list of RestrictInfo nodes to apply to
the join, as in JoinPaths, if they represent foreign and custom scans
replacing a join with a scan, and by 2) modifying create_scan_plan() in
createplan.c to use that list in that case, instead of the
baserestrictinfo list, to get pseudoconstant quals assigned to the join;
but #1 would cause an ABI break. So fix by modifying the infrastructure
to just disallow replacing joins with such quals.
Back-patch to all supported branches.
Reported by Nishant Sharma. Patch by me, reviewed by Nishant Sharma and
Richard Guo.
Discussion: https://postgr.es/m/CADrsxdbcN1vejBaf8a%2BQhrZY5PXL-04mCd4GDu6qm6FigDZd6Q%40mail.gmail.com
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The test inserted 70k rows into a foreign table, in order to verify
correct behavior with more than 65535 parameters, and was added in
response to a bug report.
However, this is rather expensive, especially when running the tests
under valgrind, CLOBBER_CACHE_ALWAYS etc. It doesn't seem worth it to
keep running the test, so remove it from all branches (14+).
Backpatch-through: 14
Discussion: https://postgr.es/m/2131017.1623451468@sss.pgh.pa.us
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