The logic around shm_mq_detach was a few bricks shy of a load, because
(contrary to the comments for shm_mq_attach) all it did was update the
shared shm_mq state. That left us leaking a bit of process-local
memory, but much worse, the on_dsm_detach callback for shm_mq_detach
was still armed. That means that whenever we ultimately detach from
the DSM segment, we'd run shm_mq_detach again for already-detached,
possibly long-dead queues. This accidentally fails to fail today,
because we only ever re-use a shm_mq's memory for another shm_mq, and
multiple detach attempts on the last such shm_mq are fairly harmless.
But it's gonna bite us someday, so let's clean it up.
To do that, change shm_mq_detach's API so it takes a shm_mq_handle
not the underlying shm_mq. This makes the callers simpler in most
cases anyway. Also fix a few places in parallel.c that were just
pfree'ing the handle structs rather than doing proper cleanup.
Back-patch to v10 because of the risk that the revenant shm_mq_detach
callbacks would cause a live bug sometime. Since this is an API
change, it's too late to do it in 9.6. (We could make a variant
patch that preserves API, but I'm not excited enough to do that.)
Discussion: https://postgr.es/m/8670.1504192177@sss.pgh.pa.us
Comment the fields of GatherMergeState, and organize them a bit more
sensibly. Comment GMReaderTupleBuffer more usefully too. Improve
assorted other comments that were obsolete or just not very good English.
Get rid of the use of a GMReaderTupleBuffer for the leader process;
that was confusing, since only the "done" field was used, and that
in a way redundant with need_to_scan_locally.
In gather_merge_init, avoid calling load_tuple_array for
already-known-exhausted workers. I'm not sure if there's a live bug there,
but the case is unlikely to be well tested due to timing considerations.
Remove some useless code, such as duplicating the tts_isempty test done by
TupIsNull.
Remove useless initialization of ps.qual, replacing that with an assertion
that we have no qual to check. (If we did, the code would fail to check
it.)
Avoid applying heap_copytuple to a null tuple. While that fails to crash,
it's confusing and it makes the code less legible not more so IMO.
Propagate a couple of these changes into nodeGather.c, as well.
Back-patch to v10, partly because of the possibility that the
gather_merge_init change is fixing a live bug, but mostly to keep
the branches in sync to ease future bug fixes.
Previously, the parallel executor logic did reinitialization of shared
state within the ExecReScan code for parallel-aware scan nodes. This is
problematic, because it means that the ExecReScan call has to occur
synchronously (ie, during the parent Gather node's ReScan call). That is
swimming very much against the tide so far as the ExecReScan machinery is
concerned; the fact that it works at all today depends on a lot of fragile
assumptions, such as that no plan node between Gather and a parallel-aware
scan node is parameterized. Another objection is that because ExecReScan
might be called in workers as well as the leader, hacky extra tests are
needed in some places to prevent unwanted shared-state resets.
Hence, let's separate this code into two functions, a ReInitializeDSM
call and the ReScan call proper. ReInitializeDSM is called only in
the leader and is guaranteed to run before we start new workers.
ReScan is returned to its traditional function of resetting only local
state, which means that ExecReScan's usual habits of delaying or
eliminating child rescan calls are safe again.
As with the preceding commit 7df2c1f8d, it doesn't seem to be necessary
to make these changes in 9.6, which is a good thing because the FDW and
CustomScan APIs are impacted.
Discussion: https://postgr.es/m/CAA4eK1JkByysFJNh9M349u_nNjqETuEnY_y1VUc_kJiU0bxtaQ@mail.gmail.com
The ExecReScan machinery contains various optimizations for postponing
or skipping rescans of plan subtrees; for example a HashAgg node may
conclude that it can re-use the table it built before, instead of
re-reading its input subtree. But that is wrong if the input contains
a parallel-aware table scan node, since the portion of the table scanned
by the leader process is likely to vary from one rescan to the next.
This explains the timing-dependent buildfarm failures we saw after
commit a2b70c89c.
The established mechanism for showing that a plan node's output is
potentially variable is to mark it as depending on some runtime Param.
Hence, to fix this, invent a dummy Param (one that has a PARAM_EXEC
parameter number, but carries no actual value) associated with each Gather
or GatherMerge node, mark parallel-aware nodes below that node as dependent
on that Param, and arrange for ExecReScanGather[Merge] to flag that Param
as changed whenever the Gather[Merge] node is rescanned.
This solution breaks an undocumented assumption made by the parallel
executor logic, namely that all rescans of nodes below a Gather[Merge]
will happen synchronously during the ReScan of the top node itself.
But that's fundamentally contrary to the design of the ExecReScan code,
and so was doomed to fail someday anyway (even if you want to argue
that the bug being fixed here wasn't a failure of that assumption).
A follow-on patch will address that issue. In the meantime, the worst
that's expected to happen is that given very bad timing luck, the leader
might have to do all the work during a rescan, because workers think
they have nothing to do, if they are able to start up before the eventual
ReScan of the leader's parallel-aware table scan node has reset the
shared scan state.
Although this problem exists in 9.6, there does not seem to be any way
for it to manifest there. Without GatherMerge, it seems that a plan tree
that has a rescan-short-circuiting node below Gather will always also
have one above it that will short-circuit in the same cases, preventing
the Gather from being rescanned. Hence we won't take the risk of
back-patching this change into 9.6. But v10 needs it.
Discussion: https://postgr.es/m/CAA4eK1JkByysFJNh9M349u_nNjqETuEnY_y1VUc_kJiU0bxtaQ@mail.gmail.com
The formatting of the sidebar element didn't carry over to the new tool
chain. Instead of inventing a whole new way of dealing with it, just
convert the one use to a "note".
As long as PQntuples, PQgetvalue, etc, use "int" for row numbers, we're
pretty much stuck with this limitation. The documentation formerly stated
that the result of PQntuples "might overflow on 32-bit operating systems",
which is just nonsense: that's not where the overflow would happen, and
if you did reach an overflow it would not be on a 32-bit machine, because
you'd have OOM'd long since.
Discussion: https://postgr.es/m/CA+FnnTxyLWyjY1goewmJNxC==HQCCF4fKkoCTa9qR36oRAHDPw@mail.gmail.com
Adding more than 1 billion rows to a PGresult would overflow its ntups and
tupArrSize fields, leading to client crashes. It'd be desirable to use
wider fields on 64-bit machines, but because all of libpq's external APIs
use plain "int" for row counters, that's going to be hard to accomplish
without an ABI break. Given the lack of complaints so far, and the general
pain that would be involved in using such huge PGresults, let's settle for
just preventing the overflow and reporting a useful error message if it
does happen. Also, for a couple more lines of code we can increase the
threshold of trouble from INT_MAX/2 to INT_MAX rows.
To do that, refactor pqAddTuple() to allow returning an error message that
replaces the default assumption that it failed because of out-of-memory.
Along the way, fix PQsetvalue() so that it reports all failures via
pqInternalNotice(). It already did so in the case of bad field number,
but neglected to report anything for other error causes.
Because of the potential for crashes, this seems like a back-patchable
bug fix, despite the lack of field reports.
Michael Paquier, per a complaint from Igor Korot.
Discussion: https://postgr.es/m/CA+FnnTxyLWyjY1goewmJNxC==HQCCF4fKkoCTa9qR36oRAHDPw@mail.gmail.com
Fix thinko in commit 8be8510cf: it's okay to have dbid == 0 in normal
(non-pin) entries in pg_shdepend, because global objects such as
databases are entered that way. The test would pass so long as it
was run in a cluster containing no databases/tablespaces owned by,
or granted to, roles other than the bootstrap superuser. That's the
expected situation for "make check", but for "make installcheck", not
so much.
Reported by Ryan Murphy.
Discussion: https://postgr.es/m/CAHeEsBc6EQe0mxGBKDXAwJbntgfvoAd5MQC-5362SmC3Tng_6g@mail.gmail.com
The string "% of total" was marked by xgettext to be a c-format, but it
is actually not, so mark up the source to prevent that.
Compute the column widths of the final display dynamically based on the
translated strings, so that translations don't mess up the display
accidentally.
Our documentation hasn't really caught up with the fact that
non-exclusive backups can now be taken using pg_start_backup and
pg_stop_backup even on standbys. Update, also correcting some
errors introduced by 52f8a59dd9.
Updates to the 9.6 documentation are needed as well, but that
will need a separate patch as some things are different on that
version.
David Steele, reviewed by Robert Haas and Michael Paquier
Discussion: http://postgr.es/m/d4d951b9-89c0-6bc1-b6ff-d0b2dd5a8966@pgmasters.net
Commit 16be2fd100 added DSA_ALLOC_HUGE,
DSA_ALLOC_ZERO and DSA_ALLOC_NO_OOM which have the same numerical
values and meanings as the similarly named MCXT_... macros. In one
place we accidentally used MCXT_ALLOC_NO_OOM when DSA_ALLOC_NO_OOM is
wanted, so tidy that up.
Author: Thomas Munro
Discussion: http://postgr.es/m/CAEepm=2AimHxVkkxnMfQvbZMkXy0uKbVa0-D38c5-qwrCm4CMQ@mail.gmail.com
Backpatch: 10, where dsa was introduced.
Remove code meant for upgrading to a particular version of PostgreSQL
9.0. Since pg_upgrade only supports upgrading to the current major
version, this code is no longer useful.
2cd7084524 / c6293249d change the way individual attributes in a
TupleDesc are stored / accessed. To reduce the effort of making
extensions compatible with postgresql 11, and to ease future
backpatching, backpatch introduction of TupleDescAttr() to all
releases. Do not backpatch change in storage, as that'd be a breaking
change for existing and working extensions.
Author: Andres Freund
Discussion: https://postgr.es/m/20170820181723.tdswdinzptbcwhrr@alap3.anarazel.de
Backpatch: 9.2-
Users can still create them themselves. Instead, document Unicode TR 35
collation options for ICU, so users can create all this themselves.
Reviewed-by: Peter Geoghegan <pg@bowt.ie>
Install language+region combinations even if they are not distinct from
the language's base locale. This gives better long-term stability of
the set of predefined locales and makes the predefined locales less
implementation-dependent and more practical for users.
Reviewed-by: Peter Geoghegan <pg@bowt.ie>
It appeared in a conditional that excludes AIX, Cygwin and MinGW. Give
ICU support a chance to work on those platforms. Back-patch to v10,
where ICU support was introduced.
Commit 3eb9a5e7c unintentionally introduced an ordering dependency
into restore_toc_entries_prefork(). The existing coding of
reduce_dependencies() contains a check to skip moving a TOC entry
to the ready_list if it wasn't initially in the pending_list.
This used to suffice to prevent reduce_dependencies() from trying to
move anything into the ready_list during restore_toc_entries_prefork(),
because the pending_list stayed empty throughout that phase; but it no
longer does. The problem doesn't manifest unless the TOC has been
reordered by SortTocFromFile, which is how I missed it in testing.
To fix, just add a test for ready_list == NULL, converting the call
with NULL from a poor man's sanity check into an explicit command
not to touch TOC items' list membership. Clarify some of the comments
around this; in particular, note the primary purpose of the check for
pending_list membership, which is to ensure that we can't try to restore
the same item twice, in case a TOC list forces it to be restored before
its dependency count goes to zero.
Per report from Fabrízio de Royes Mello. Back-patch to 9.3, like the
previous commit.
Discussion: https://postgr.es/m/CAFcNs+pjuv0JL_x4+=71TPUPjdLHOXA4YfT32myj_OrrZb4ohA@mail.gmail.com
Add a new EState member es_leaf_result_relations, so that the trigger
code knows about ResultRelInfos created by tuple routing. Also make
sure ExplainPrintTriggers knows about partition-related
ResultRelInfos.
Etsuro Fujita, reviewed by Amit Langote
Discussion: http://postgr.es/m/57163e18-8e56-da83-337a-22f2c0008051@lab.ntt.co.jp
That code patch was good as far as it went, but the associated test case
has exposed fundamental brain damage in the parallel scan mechanism,
which is going to take nontrivial work to correct. In the interests of
getting the buildfarm back to green so that unrelated work can proceed,
let's temporarily remove the test case.
Instead, lock them in the caller using find_all_inheritors so that
they get locked in the standard order, minimizing deadlock risks.
Also in RelationGetPartitionDispatchInfo, avoid opening tables which
are not partitioned; there's no need.
Amit Langote, reviewed by Ashutosh Bapat and Amit Khandekar
Discussion: http://postgr.es/m/91b36fa1-c197-b72f-ca6e-56c593bae68c@lab.ntt.co.jp
It now emerges that we can only rely on Perl to tell us we must use
-D_USE_32BIT_TIME_T if it's Perl 5.13.4 or later. For older versions,
revert to our previous practice of assuming we need that symbol in
all 32-bit Windows builds. This is not ideal, but inquiring into
which compiler version Perl was built with seems far too fragile.
In any case, we had not previously had complaints about these old
Perl versions, so let's assume this is Good Enough. (It's still
better than the situation ante commit 5a5c2feca, in that at least
the effects are confined to PL/Perl rather than the whole PG build.)
Back-patch to all supported versions, like 5a5c2feca and predecessors.
Discussion: https://postgr.es/m/CANFyU97OVQ3+Mzfmt3MhuUm5NwPU=-FtbNH5Eb7nZL9ua8=rcA@mail.gmail.com
This became possible by commit
6c2003f8a1. This just makes pg_dump aware
of it and updates the documentation.
Author: Petr Jelinek <petr.jelinek@2ndquadrant.com>
Although not confirmed and probably rare, if the newly allocated memory
is not already zero, this could possibly have caused some problems.
Also reorder the initializations slightly so they match the order of the
struct definition.
Author: Wong, Yi Wen <yiwong@amazon.com>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
