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As pointed out by Tom Lane, the patch introduced fragile and invasive
design around plan invalidation handling when locking of prunable
partitions was deferred from plancache.c to the executor. In
particular, it violated assumptions about CachedPlan immutability and
altered executor APIs in ways that are difficult to justify given the
added complexity and overhead.
This also removes the firstResultRels field added to PlannedStmt in
commit 28317de72, which was intended to support deferred locking of
certain ModifyTable result relations.
Reported-by: Tom Lane <[email protected]>
Discussion: https://postgr.es/m/[email protected]
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Before executing a cached generic plan, AcquireExecutorLocks() in
plancache.c locks all relations in a plan's range table to ensure the
plan is safe for execution. However, this locks runtime-prunable
relations that will later be pruned during "initial" runtime pruning,
introducing unnecessary overhead.
This commit defers locking for such relations to executor startup and
ensures that if the CachedPlan is invalidated due to concurrent DDL
during this window, replanning is triggered. Deferring these locks
avoids unnecessary locking overhead for pruned partitions, resulting
in significant speedup, particularly when many partitions are pruned
during initial runtime pruning.
* Changes to locking when executing generic plans:
AcquireExecutorLocks() now locks only unprunable relations, that is,
those found in PlannedStmt.unprunableRelids (introduced in commit
cbc127917e), to avoid locking runtime-prunable partitions
unnecessarily. The remaining locks are taken by
ExecDoInitialPruning(), which acquires them only for partitions that
survive pruning.
This deferral does not affect the locks required for permission
checking in InitPlan(), which takes place before initial pruning.
ExecCheckPermissions() now includes an Assert to verify that all
relations undergoing permission checks, none of which can be in the
set of runtime-prunable relations, are properly locked.
* Plan invalidation handling:
Deferring locks introduces a window where prunable relations may be
altered by concurrent DDL, invalidating the plan. A new function,
ExecutorStartCachedPlan(), wraps ExecutorStart() to detect and handle
invalidation caused by deferred locking. If invalidation occurs,
ExecutorStartCachedPlan() updates CachedPlan using the new
UpdateCachedPlan() function and retries execution with the updated
plan. To ensure all code paths that may be affected by this handle
invalidation properly, all callers of ExecutorStart that may execute a
PlannedStmt from a CachedPlan have been updated to use
ExecutorStartCachedPlan() instead.
UpdateCachedPlan() replaces stale plans in CachedPlan.stmt_list. A new
CachedPlan.stmt_context, created as a child of CachedPlan.context,
allows freeing old PlannedStmts while preserving the CachedPlan
structure and its statement list. This ensures that loops over
statements in upstream callers of ExecutorStartCachedPlan() remain
intact.
ExecutorStart() and ExecutorStart_hook implementations now return a
boolean value indicating whether plan initialization succeeded with a
valid PlanState tree in QueryDesc.planstate, or false otherwise, in
which case QueryDesc.planstate is NULL. Hook implementations are
required to call standard_ExecutorStart() at the beginning, and if it
returns false, they should do the same without proceeding.
* Testing:
To verify these changes, the delay_execution module tests scenarios
where cached plans become invalid due to changes in prunable relations
after deferred locks.
* Note to extension authors:
ExecutorStart_hook implementations must verify plan validity after
calling standard_ExecutorStart(), as explained earlier. For example:
if (prev_ExecutorStart)
plan_valid = prev_ExecutorStart(queryDesc, eflags);
else
plan_valid = standard_ExecutorStart(queryDesc, eflags);
if (!plan_valid)
return false;
<extension-code>
return true;
Extensions accessing child relations, especially prunable partitions,
via ExecGetRangeTableRelation() must now ensure their RT indexes are
present in es_unpruned_relids (introduced in commit cbc127917e), or
they will encounter an error. This is a strict requirement after this
change, as only relations in that set are locked.
The idea of deferring some locks to executor startup, allowing locks
for prunable partitions to be skipped, was first proposed by Tom Lane.
Reviewed-by: Robert Haas <[email protected]> (earlier versions)
Reviewed-by: David Rowley <[email protected]> (earlier versions)
Reviewed-by: Tom Lane <[email protected]> (earlier versions)
Reviewed-by: Tomas Vondra <[email protected]>
Reviewed-by: Junwang Zhao <[email protected]>
Discussion: https://postgr.es/m/CA+HiwqFGkMSge6TgC9KQzde0ohpAycLQuV7ooitEEpbKB0O_mg@mail.gmail.com
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Backpatch-through: 13
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pg_cursor() supposed that any Portal it finds in the hash table must
have sourceText set up, but there's an edge case where that is not so.
A newly-created Portal has sourceText = NULL, and that doesn't change
until PortalDefineQuery is called. In SPI_cursor_open_internal,
we perform GetCachedPlan between CreatePortal and PortalDefineQuery,
and it's possible for user-defined code to execute during that
planning and cause a fetch from the pg_cursors view, resulting in a
null-pointer-dereference crash. (It looks like the same could happen
in exec_bind_message, but I've not tried to provoke a failure there.)
I considered trying to fix this by setting sourceText sooner, but
there may be instances of this same calling pattern in extensions,
and we couldn't be sure they'd get the memo promptly. It seems
better to redefine pg_cursor as not showing Portals that have
not yet had PortalDefineQuery called on them, which we can do by
just skipping them if sourceText is still NULL.
(Before a1c692358, pg_cursor would instead return a row with NULL
in the statement column. We could revert to that behavior but it
doesn't really seem like a better definition, especially since our
documentation doesn't suggest that the column could be NULL.)
Per report from PetSerAl. Back-patch to all supported branches.
Discussion: https://postgr.es/m/CAKygsHTBXLXjwV43kpZa+Cs+XTiaeeJiZdL4cPBm9f4MTdw7wg@mail.gmail.com
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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
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Reported-by: Michael Paquier
Discussion: https://postgr.es/m/[email protected]
Backpatch-through: 12
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Backpatch-through: 11
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These don't offer anything over plain Assert, and their usage had
already been declared obsolescent.
Author: Nathan Bossart <[email protected]>
Reviewed-by: Michael Paquier <[email protected]>
Discussion: https://www.postgresql.org/message-id/20221009210148.GA900071@nathanxps13
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Per discussion, the existing routine name able to initialize a SRF
function with materialize mode is unpopular, so rename it. Equally, the
flags of this function are renamed, as of:
- SRF_SINGLE_USE_EXPECTED -> MAT_SRF_USE_EXPECTED_DESC
- SRF_SINGLE_BLESS -> MAT_SRF_BLESS
The previous function and flags introduced in 9e98583 are kept around
for compatibility purposes, so as any extension code already compiled
with v15 continues to work as-is. The declarations introduced here for
compatibility will be removed from HEAD in a follow-up commit.
The new names have been suggested by Andres Freund and Melanie
Plageman.
Discussion: https://postgr.es/m/[email protected]
Backpatch-through: 15
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This replaces all MemSet() calls with struct initialization where that
is easily and obviously possible. (For example, some cases have to
worry about padding bits, so I left those.)
(The same could be done with appropriate memset() calls, but this
patch is part of an effort to phase out MemSet(), so it doesn't touch
memset() calls.)
Reviewed-by: Ranier Vilela <[email protected]>
Reviewed-by: Alvaro Herrera <[email protected]>
Discussion: https://www.postgresql.org/message-id/[email protected]
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Set-returning functions that use the Materialize mode, creating a
tuplestore to include all the tuples returned in a set rather than doing
so in multiple calls, use roughly the same set of steps to prepare
ReturnSetInfo for this job:
- Check if ReturnSetInfo supports returning a tuplestore and if the
materialize mode is enabled.
- Create a tuplestore for all the tuples part of the returned set in the
per-query memory context, stored in ReturnSetInfo->setResult.
- Build a tuple descriptor mostly from get_call_result_type(), then
stored in ReturnSetInfo->setDesc. Note that there are some cases where
the SRF's tuple descriptor has to be the one specified by the function
caller.
This refactoring is done so as there are (well, should be) no behavior
changes in any of the in-core functions refactored, and the centralized
function that checks and sets up the function's ReturnSetInfo can be
controlled with a set of bits32 options. Two of them prove to be
necessary now:
- SRF_SINGLE_USE_EXPECTED to use expectedDesc as tuple descriptor, as
expected by the function's caller.
- SRF_SINGLE_BLESS to validate the tuple descriptor for the SRF.
The same initialization pattern is simplified in 28 places per my
count as of src/backend/, shaving up to ~900 lines of code. These
mostly come from the removal of the per-query initializations and the
sanity checks now grouped in a single location. There are more
locations that could be simplified in contrib/, that are left for a
follow-up cleanup.
fcc2817, 07daca5 and d61a361 have prepared the areas of the code related
to this change, to ease this refactoring.
Author: Melanie Plageman, Michael Paquier
Reviewed-by: Álvaro Herrera, Justin Pryzby
Discussion: https://postgr.es/m/CAAKRu_azyd1Z3W_r7Ou4sorTjRCs+PxeHw1CWJeXKofkE6TuZg@mail.gmail.com
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SPI_commit previously left it up to the caller to recover from any error
occurring during commit. Since that's complicated and requires use of
low-level xact.c facilities, it's not too surprising that no caller got
it right. Let's move the responsibility for cleanup into spi.c. Doing
that requires redefining SPI_commit as starting a new transaction, so
that it becomes equivalent to SPI_commit_and_chain except that you get
default transaction characteristics instead of preserving the prior
transaction's characteristics. We can make this pretty transparent
API-wise by redefining SPI_start_transaction() as a no-op. Callers
that expect to do something in between might be surprised, but
available evidence is that no callers do so.
Having made that API redefinition, we can fix this mess by having
SPI_commit[_and_chain] trap errors and start a new, clean transaction
before re-throwing the error. Likewise for SPI_rollback[_and_chain].
Some cleanup is also needed in AtEOXact_SPI, which was nowhere near
smart enough to deal with SPI contexts nested inside a committing
context.
While plperl and pltcl need no changes beyond removing their now-useless
SPI_start_transaction() calls, plpython needs some more work because it
hadn't gotten the memo about catching commit/rollback errors in the
first place. Such an error resulted in longjmp'ing out of the Python
interpreter, which leaks Python stack entries at present and is reported
to crash Python 3.11 altogether. Add the missing logic to catch such
errors and convert them into Python exceptions.
We are probably going to have to back-patch this once Python 3.11 ships,
but it's a sufficiently basic change that I'm a bit nervous about doing
so immediately. Let's let it bake awhile in HEAD first.
Peter Eisentraut and Tom Lane
Discussion: https://postgr.es/m/[email protected]
Discussion: https://postgr.es/m/[email protected]
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The following set-returning functions have their logic simplified, to be
more consistent with other in-core areas:
- pg_prepared_statement()'s tuple descriptor is now created with
get_call_result_type() instead of being created from scratch, saving
from some duplication with pg_proc.dat.
- show_all_file_settings(), similarly, now uses get_call_result_type()
to build its tuple descriptor instead of creating it from scratch.
- pg_options_to_table() made use of a static routine called only once.
This commit removes this internal routine to make the function easier to
follow.
- pg_config() was using a unique logic style, doing checks on the tuple
descriptor passed down in expectedDesc, but it has no need to do so.
This switches the function to use a tuplestore with a tuple descriptor
retrieved from get_call_result_type(), instead.
This simplifies an upcoming patch aimed at refactoring the way
tuplestores are created and checked in set-returning functions, this
change making sense as its own independent cleanup by shaving some
code.
Author: Melanie Plageman, Michael Paquier
Reviewed-by: Justin Pryzby
Discussion: https://postgr.es/m/CAAKRu_azyd1Z3W_r7Ou4sorTjRCs+PxeHw1CWJeXKofkE6TuZg@mail.gmail.com
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This routine is a no-op since dd04e95 from 2003, with a macro kept
around for compatibility purposes. This has led to the same code
patterns being copy-pasted around for no effect, sometimes in confusing
ways like in pg_logical_slot_get_changes_guts() from logical.c where the
code was actually incorrect.
This issue has been discussed on two different threads recently, so
rather than living with this legacy, remove any uses of this routine in
the C code to simplify things. The compatibility macro is kept to avoid
breaking any out-of-core modules that depend on it.
Reported-by: Tatsuhito Kasahara, Justin Pryzby
Author: Tatsuhito Kasahara
Discussion: https://postgr.es/m/[email protected]
Discussion: https://postgr.es/m/CAP0=ZVJeeYfAeRfmzqAF2Lumdiv4S4FewyBnZd4DPTrsSQKJKw@mail.gmail.com
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Backpatch-through: 10
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Commit 84f5c2908 forgot to consider the possibility that
EnsurePortalSnapshotExists could run inside a subtransaction with
lifespan shorter than the Portal's. In that case, the new active
snapshot would be popped at the end of the subtransaction, leaving
a dangling pointer in the Portal, with mayhem ensuing.
To fix, make sure the ActiveSnapshot stack entry is marked with
the same subtransaction nesting level as the associated Portal.
It's certainly safe to do so since we won't be here at all unless
the stack is empty; hence we can't create an out-of-order stack.
Let's also apply this logic in the case where PortalRunUtility
sets portalSnapshot, just to be sure that path can't cause similar
problems. It's slightly less clear that that path can't create
an out-of-order stack, so add an assertion guarding it.
Report and patch by Bertrand Drouvot (with kibitzing by me).
Back-patch to v11, like the previous commit.
Discussion: https://postgr.es/m/[email protected]
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COMMIT/ROLLBACK necessarily destroys all snapshots within the session.
The original implementation of intra-procedure transactions just
cavalierly did that, ignoring the fact that this left us executing in
a rather different environment than normal. In particular, it turns
out that handling of toasted datums depends rather critically on there
being an outer ActiveSnapshot: otherwise, when SPI or the core
executor pop whatever snapshot they used and return, it's unsafe to
dereference any toasted datums that may appear in the query result.
It's possible to demonstrate "no known snapshots" and "missing chunk
number N for toast value" errors as a result of this oversight.
Historically this outer snapshot has been held by the Portal code,
and that seems like a good plan to preserve. So add infrastructure
to pquery.c to allow re-establishing the Portal-owned snapshot if it's
not there anymore, and add enough bookkeeping support that we can tell
whether it is or not.
We can't, however, just re-establish the Portal snapshot as part of
COMMIT/ROLLBACK. As in normal transaction start, acquiring the first
snapshot should wait until after SET and LOCK commands. Hence, teach
spi.c about doing this at the right time. (Note that this patch
doesn't fix the problem for any PLs that try to run intra-procedure
transactions without using SPI to execute SQL commands.)
This makes SPI's no_snapshots parameter rather a misnomer, so in HEAD,
rename that to allow_nonatomic.
replication/logical/worker.c also needs some fixes, because it wasn't
careful to hold a snapshot open around AFTER trigger execution.
That code doesn't use a Portal, which I suspect someday we're gonna
have to fix. But for now, just rearrange the order of operations.
This includes back-patching the recent addition of finish_estate()
to centralize the cleanup logic there.
This also back-patches commit 2ecfeda3e into v13, to improve the
test coverage for worker.c (it was that test that exposed that
worker.c's snapshot management is wrong).
Per bug #15990 from Andreas Wicht. Back-patch to v11 where
intra-procedure COMMIT was added.
Discussion: https://postgr.es/m/[email protected]
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This patch essentially is cleaning up technical debt left behind
by the original implementation of plpgsql procedures, particularly
commit d92bc83c4. That patch (or more precisely, follow-on patches
fixing its worst bugs) forced us to re-plan CALL and DO statements
each time through, if we're in a non-atomic context. That wasn't
for any fundamental reason, but just because use of a saved plan
requires having a ResourceOwner to hold a reference count for the
plan, and we had no suitable resowner at hand, nor would the
available APIs support using one if we did. While it's not that
expensive to create a "plan" for CALL/DO, the cycles do add up
in repeated executions.
This patch therefore makes the following API changes:
* GetCachedPlan/ReleaseCachedPlan are modified to let the caller
specify which resowner to use to pin the plan, rather than forcing
use of CurrentResourceOwner.
* spi.c gains a "SPI_execute_plan_extended" entry point that lets
callers say which resowner to use to pin the plan. This borrows the
idea of an options struct from the recently added SPI_prepare_extended,
hopefully allowing future options to be added without more API breaks.
This supersedes SPI_execute_plan_with_paramlist (which I've marked
deprecated) as well as SPI_execute_plan_with_receiver (which is new
in v14, so I just took it out altogether).
* I also took the opportunity to remove the crude hack of letting
plpgsql reach into SPI private data structures to mark SPI plans as
"no_snapshot". It's better to treat that as an option of
SPI_prepare_extended.
Now, when running a non-atomic procedure or DO block that contains
any CALL or DO commands, plpgsql creates a ResourceOwner that
will be used to pin the plans of the CALL/DO commands. (In an
atomic context, we just use CurrentResourceOwner, as before.)
Having done this, we can just save CALL/DO plans normally,
whether or not they are used across transaction boundaries.
This seems to be good for something like 2X speedup of a CALL
of a trivial procedure with a few simple argument expressions.
By restricting the creation of an extra ResourceOwner like this,
there's essentially zero penalty in cases that can't benefit.
Pavel Stehule, with some further hacking by me
Discussion: https://postgr.es/m/CAFj8pRCLPdDAETvR7Po7gC5y_ibkn_-bOzbeJb39WHms01194Q@mail.gmail.com
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Backpatch-through: 9.5
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Invent a new flag bit HASH_STRINGS to specify C-string hashing, which
was formerly the default; and add assertions insisting that exactly
one of the bits HASH_STRINGS, HASH_BLOBS, and HASH_FUNCTION be set.
This is in hopes of preventing recurrences of the type of oversight
fixed in commit a1b8aa1e4 (i.e., mistakenly omitting HASH_BLOBS).
Also, when HASH_STRINGS is specified, insist that the keysize be
more than 8 bytes. This is a heuristic, but it should catch
accidental use of HASH_STRINGS for integer or pointer keys.
(Nearly all existing use-cases set the keysize to NAMEDATALEN or
more, so there's little reason to think this restriction should
be problematic.)
Tweak hash_create() to insist that the HASH_ELEM flag be set, and
remove the defaults it had for keysize and entrysize. Since those
defaults were undocumented and basically useless, no callers
omitted HASH_ELEM anyway.
Also, remove memset's zeroing the HASHCTL parameter struct from
those callers that had one. This has never been really necessary,
and while it wasn't a bad coding convention it was confusing that
some callers did it and some did not. We might as well save a few
cycles by standardizing on "not".
Also improve the documentation for hash_create().
In passing, improve reinit.c's usage of a hash table by storing
the key as a binary Oid rather than a string; and, since that's
a temporary hash table, allocate it in CurrentMemoryContext for
neatness.
Discussion: https://postgr.es/m/[email protected]
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Otherwise just printing an empty string makes the memory context debug
output slightly confusing.
Discussion: https://www.postgresql.org/message-id/flat/ccb353ef-89ff-09b3-8046-1d2514624b9c%402ndquadrant.com
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The backend was using strings to represent command tags and doing string
comparisons in multiple places, but that's slow and unhelpful. Create a
new command list with a supporting structure to use instead; this is
stored in a tag-list-file that can be tailored to specific purposes with
a caller-definable C macro, similar to what we do for WAL resource
managers. The first first such uses are a new CommandTag enum and a
CommandTagBehavior struct.
Replace numerous occurrences of char *completionTag with a
QueryCompletion struct so that the code no longer stores information
about completed queries in a cstring. Only at the last moment, in
EndCommand(), does this get converted to a string.
EventTriggerCacheItem no longer holds an array of palloc’d tag strings
in sorted order, but rather just a Bitmapset over the CommandTags.
Author: Mark Dilger, with unsolicited help from Álvaro Herrera
Reviewed-by: John Naylor, Tom Lane
Discussion: https://postgr.es/m/[email protected]
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Backpatch-through: update all files in master, backpatch legal files through 9.4
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Using \ is unnecessary and ugly, so remove that. While at it, stitch
the literals back into a single line: we've long discouraged splitting
error message literals even when they go past the 80 chars line limit,
to improve greppability.
Leave contrib/tablefunc alone.
Discussion: https://postgr.es/m/[email protected]
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HoldPinnedPortals() did things in the wrong order: it must not mark
a portal autoHeld until it's been successfully held. Otherwise,
a failure while persisting the portal results in a server crash
because we think the portal is in a good state when it's not.
Also add a check that portal->status is READY before attempting to
hold a pinned portal. We have such a check before the only other
use of HoldPortal(), so it seems unwise not to check it here.
Lastly, rethink the responsibility for where to call HoldPinnedPortals.
The comment for it imagined that it was optional for any individual PL
to call it or not, but that cannot be the case: if some outer level of
procedure has a pinned portal, failing to persist it when an inner
procedure commits is going to be trouble. Let's have SPI do it instead
of the individual PLs. That's not a complete solution, since in theory
a PL might not be using SPI to perform commit/rollback, but such a PL
is going to have to be aware of lots of related requirements anyway.
(This change doesn't cause an API break for any external PLs that might
be calling HoldPinnedPortals per the old regime, because calling it
twice during a commit or rollback sequence won't hurt.)
Per bug #15703 from Julian Schauder. Back-patch to v11 where this code
came in.
Discussion: https://postgr.es/m/[email protected]
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Backpatch-through: certain files through 9.4
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Previously tables declared WITH OIDS, including a significant fraction
of the catalog tables, stored the oid column not as a normal column,
but as part of the tuple header.
This special column was not shown by default, which was somewhat odd,
as it's often (consider e.g. pg_class.oid) one of the more important
parts of a row. Neither pg_dump nor COPY included the contents of the
oid column by default.
The fact that the oid column was not an ordinary column necessitated a
significant amount of special case code to support oid columns. That
already was painful for the existing, but upcoming work aiming to make
table storage pluggable, would have required expanding and duplicating
that "specialness" significantly.
WITH OIDS has been deprecated since 2005 (commit ff02d0a05280e0).
Remove it.
Removing includes:
- CREATE TABLE and ALTER TABLE syntax for declaring the table to be
WITH OIDS has been removed (WITH (oids[ = true]) will error out)
- pg_dump does not support dumping tables declared WITH OIDS and will
issue a warning when dumping one (and ignore the oid column).
- restoring an pg_dump archive with pg_restore will warn when
restoring a table with oid contents (and ignore the oid column)
- COPY will refuse to load binary dump that includes oids.
- pg_upgrade will error out when encountering tables declared WITH
OIDS, they have to be altered to remove the oid column first.
- Functionality to access the oid of the last inserted row (like
plpgsql's RESULT_OID, spi's SPI_lastoid, ...) has been removed.
The syntax for declaring a table WITHOUT OIDS (or WITH (oids = false)
for CREATE TABLE) is still supported. While that requires a bit of
support code, it seems unnecessary to break applications / dumps that
do not use oids, and are explicit about not using them.
The biggest user of WITH OID columns was postgres' catalog. This
commit changes all 'magic' oid columns to be columns that are normally
declared and stored. To reduce unnecessary query breakage all the
newly added columns are still named 'oid', even if a table's column
naming scheme would indicate 'reloid' or such. This obviously
requires adapting a lot code, mostly replacing oid access via
HeapTupleGetOid() with access to the underlying Form_pg_*->oid column.
The bootstrap process now assigns oids for all oid columns in
genbki.pl that do not have an explicit value (starting at the largest
oid previously used), only oids assigned later by oids will be above
FirstBootstrapObjectId. As the oid column now is a normal column the
special bootstrap syntax for oids has been removed.
Oids are not automatically assigned during insertion anymore, all
backend code explicitly assigns oids with GetNewOidWithIndex(). For
the rare case that insertions into the catalog via SQL are called for
the new pg_nextoid() function can be used (which only works on catalog
tables).
The fact that oid columns on system tables are now normal columns
means that they will be included in the set of columns expanded
by * (i.e. SELECT * FROM pg_class will now include the table's oid,
previously it did not). It'd not technically be hard to hide oid
column by default, but that'd mean confusing behavior would either
have to be carried forward forever, or it'd cause breakage down the
line.
While it's not unlikely that further adjustments are needed, the
scope/invasiveness of the patch makes it worthwhile to get merge this
now. It's painful to maintain externally, too complicated to commit
after the code code freeze, and a dependency of a number of other
patches.
Catversion bump, for obvious reasons.
Author: Andres Freund, with contributions by John Naylor
Discussion: https://postgr.es/m/[email protected]
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The problem arises with the combination of CALL with output parameters
and doing a COMMIT inside the procedure. When a CALL has output
parameters, the portal uses the strategy PORTAL_UTIL_SELECT instead of
PORTAL_MULTI_QUERY. Using PORTAL_UTIL_SELECT causes the portal's
snapshot to be registered with the current resource
owner (portal->holdSnapshot); see
9ee1cf04ab6bcefe03a11837b53f29ca9dc24c7a for the reason.
Normally, PortalDrop() unregisters the snapshot. If not, then
ResourceOwnerRelease() will print a warning about a snapshot leak on
transaction commit. A transaction commit normally drops all
portals (PreCommit_Portals()), except the active portal. So in case of
the active portal, we need to manually release the snapshot to avoid the
warning.
Reported-by: Prabhat Sahu <[email protected]>
Reviewed-by: Jonathan S. Katz <[email protected]>
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Discussion: https://postgr.es/m/[email protected]
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Discussion: https://www.postgresql.org/message-id/[email protected]
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Previously, committing or aborting inside a cursor loop was prohibited
because that would close and remove the cursor. To allow that,
automatically convert such cursors to holdable cursors so they survive
commits or rollbacks. Portals now have a new state "auto-held", which
means they have been converted automatically from pinned. An auto-held
portal is kept on transaction commit or rollback, but is still removed
when returning to the main loop on error.
This supports all languages that have cursor loop constructs: PL/pgSQL,
PL/Python, PL/Perl.
Reviewed-by: Ildus Kurbangaliev <[email protected]>
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elog(FATAL) would end up calling PortalCleanup(), which would call
executor shutdown code, which could fail and crash, especially under
parallel query. This was introduced by
8561e4840c81f7e345be2df170839846814fa004, which did not want to mark an
active portal as failed by a normal transaction abort anymore. But we
do need to do that for an elog(FATAL) exit. Introduce a variable
shmem_exit_inprogress similar to the existing proc_exit_inprogress, so
we can tell whether we are in the FATAL exit scenario.
Reported-by: Andres Freund <[email protected]>
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In each of the supplied procedural languages (PL/pgSQL, PL/Perl,
PL/Python, PL/Tcl), add language-specific commit and rollback
functions/commands to control transactions in procedures in that
language. Add similar underlying functions to SPI. Some additional
cleanup so that transaction commit or abort doesn't blow away data
structures still used by the procedure call. Add execution context
tracking to CALL and DO statements so that transaction control commands
can only be issued in top-level procedure and block calls, not function
calls or other procedure or block calls.
- SPI
Add a new function SPI_connect_ext() that is like SPI_connect() but
allows passing option flags. The only option flag right now is
SPI_OPT_NONATOMIC. A nonatomic SPI connection can execute transaction
control commands, otherwise it's not allowed. This is meant to be
passed down from CALL and DO statements which themselves know in which
context they are called. A nonatomic SPI connection uses different
memory management. A normal SPI connection allocates its memory in
TopTransactionContext. For nonatomic connections we use PortalContext
instead. As the comment in SPI_connect_ext() (previously SPI_connect())
indicates, one could potentially use PortalContext in all cases, but it
seems safest to leave the existing uses alone, because this stuff is
complicated enough already.
SPI also gets new functions SPI_start_transaction(), SPI_commit(), and
SPI_rollback(), which can be used by PLs to implement their transaction
control logic.
- portalmem.c
Some adjustments were made in the code that cleans up portals at
transaction abort. The portal code could already handle a command
*committing* a transaction and continuing (e.g., VACUUM), but it was not
quite prepared for a command *aborting* a transaction and continuing.
In AtAbort_Portals(), remove the code that marks an active portal as
failed. As the comment there already predicted, this doesn't work if
the running command wants to keep running after transaction abort. And
it's actually not necessary, because pquery.c is careful to run all
portal code in a PG_TRY block and explicitly runs MarkPortalFailed() if
there is an exception. So the code in AtAbort_Portals() is never used
anyway.
In AtAbort_Portals() and AtCleanup_Portals(), we need to be careful not
to clean up active portals too much. This mirrors similar code in
PreCommit_Portals().
- PL/Perl
Gets new functions spi_commit() and spi_rollback()
- PL/pgSQL
Gets new commands COMMIT and ROLLBACK.
Update the PL/SQL porting example in the documentation to reflect that
transactions are now possible in procedures.
- PL/Python
Gets new functions plpy.commit and plpy.rollback.
- PL/Tcl
Gets new commands commit and rollback.
Reviewed-by: Andrew Dunstan <[email protected]>
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The previous code gave the same error message for attempting to drop
pinned and active portals, but those are separate states, so give
separate error messages.
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Rename PortalMemory to TopPortalContext, to avoid confusion with
PortalContext and align naming with similar top-level memory contexts.
Rename PortalData's "heap" field to portalContext. The "heap" naming
seems quite antiquated and confusing. Also get rid of the
PortalGetHeapMemory() macro and access the field directly, which we do
for other portal fields, so this abstraction doesn't buy anything.
Reviewed-by: Andrew Dunstan <[email protected]>
Reviewed-by: Alvaro Herrera <[email protected]>
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Backpatch-through: certain files through 9.3
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The lower case spellings are C and C++ standard and are used in most
parts of the PostgreSQL sources. The upper case spellings are only used
in some files/modules. So standardize on the standard spellings.
The APIs for ICU, Perl, and Windows define their own TRUE and FALSE, so
those are left as is when using those APIs.
In code comments, we use the lower-case spelling for the C concepts and
keep the upper-case spelling for the SQL concepts.
Reviewed-by: Michael Paquier <[email protected]>
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It is equivalent in ANSI C to write (*funcptr) () and funcptr(). These
two styles have been applied inconsistently. After discussion, we'll
use the more verbose style for plain function pointer variables, to make
it clear that it's a variable, and the shorter style when the function
pointer is in a struct (s.func() or s->func()), because then it's clear
that it's not a plain function name, and otherwise the excessive
punctuation makes some of those invocations hard to read.
Discussion: https://www.postgresql.org/message-id/[email protected]
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Stress testing by Andreas Seltenreich disclosed longstanding problems that
occur if a FATAL exit (e.g. due to receipt of SIGTERM) occurs while we are
trying to execute a ROLLBACK of an already-failed transaction. In such a
case, xact.c is in TBLOCK_ABORT state, so that AbortOutOfAnyTransaction
would skip AbortTransaction and go straight to CleanupTransaction. This
led to an assert failure in an assert-enabled build (due to the ROLLBACK's
portal still having a cleanup hook) or without assertions, to a FATAL exit
complaining about "cannot drop active portal". The latter's not
disastrous, perhaps, but it's messy enough to want to improve it.
We don't really want to run all of AbortTransaction in this code path.
The minimum required to clean up the open portal safely is to do
AtAbort_Memory and AtAbort_Portals. It seems like a good idea to
do AtAbort_Memory unconditionally, to be entirely sure that we are
starting with a safe CurrentMemoryContext. That means that if the
main loop in AbortOutOfAnyTransaction does nothing, we need an extra
step at the bottom to restore CurrentMemoryContext = TopMemoryContext,
which I chose to do by invoking AtCleanup_Memory. This'll result in
calling AtCleanup_Memory twice in many of the paths through this function,
but that seems harmless and reasonably inexpensive.
The original motivation for the assertion in AtCleanup_Portals was that
we wanted to be sure that any user-defined code executed as a consequence
of the cleanup hook runs during AbortTransaction not CleanupTransaction.
That still seems like a valid concern, and now that we've seen one case
of the assertion firing --- which means that exactly that would have
happened in a production build --- let's replace the Assert with a runtime
check. If we see the cleanup hook still set, we'll emit a WARNING and
just drop the hook unexecuted.
This has been like this a long time, so back-patch to all supported
branches.
Discussion: https://postgr.es/m/[email protected]
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This extends the castNode() notation introduced by commit 5bcab1114 to
provide, in one step, extraction of a list cell's pointer and coercion to
a concrete node type. For example, "lfirst_node(Foo, lc)" is the same
as "castNode(Foo, lfirst(lc))". Almost half of the uses of castNode
that have appeared so far include a list extraction call, so this is
pretty widely useful, and it saves a few more keystrokes compared to the
old way.
As with the previous patch, back-patch the addition of these macros to
pg_list.h, so that the notation will be available when back-patching.
Patch by me, after an idea of Andrew Gierth's.
Discussion: https://postgr.es/m/[email protected]
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When I wrote commit ab1f0c822, I really missed the castNode() macro that
Peter E. had proposed shortly before. This back-fills the uses I would
have put it to. It's probably not all that significant, but there are
more assertions here than there were before, and conceivably they will
help catch any bugs associated with those representation changes.
I left behind a number of usages like "(Query *) copyObject(query_var)".
Those could have been converted as well, but Peter has proposed another
notational improvement that would handle copyObject cases automatically,
so I let that be for now.
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This patch makes several changes that improve the consistency of
representation of lists of statements. It's always been the case
that the output of parse analysis is a list of Query nodes, whatever
the types of the individual statements in the list. This patch brings
similar consistency to the outputs of raw parsing and planning steps:
* The output of raw parsing is now always a list of RawStmt nodes;
the statement-type-dependent nodes are one level down from that.
* The output of pg_plan_queries() is now always a list of PlannedStmt
nodes, even for utility statements. In the case of a utility statement,
"planning" just consists of wrapping a CMD_UTILITY PlannedStmt around
the utility node. This list representation is now used in Portal and
CachedPlan plan lists, replacing the former convention of intermixing
PlannedStmts with bare utility-statement nodes.
Now, every list of statements has a consistent head-node type depending
on how far along it is in processing. This allows changing many places
that formerly used generic "Node *" pointers to use a more specific
pointer type, thus reducing the number of IsA() tests and casts needed,
as well as improving code clarity.
Also, the post-parse-analysis representation of DECLARE CURSOR is changed
so that it looks more like EXPLAIN, PREPARE, etc. That is, the contained
SELECT remains a child of the DeclareCursorStmt rather than getting flipped
around to be the other way. It's now true for both Query and PlannedStmt
that utilityStmt is non-null if and only if commandType is CMD_UTILITY.
That allows simplifying a lot of places that were testing both fields.
(I think some of those were just defensive programming, but in many places,
it was actually necessary to avoid confusing DECLARE CURSOR with SELECT.)
Because PlannedStmt carries a canSetTag field, we're also able to get rid
of some ad-hoc rules about how to reconstruct canSetTag for a bare utility
statement; specifically, the assumption that a utility is canSetTag if and
only if it's the only one in its list. While I see no near-term need for
relaxing that restriction, it's nice to get rid of the ad-hocery.
The API of ProcessUtility() is changed so that what it's passed is the
wrapper PlannedStmt not just the bare utility statement. This will affect
all users of ProcessUtility_hook, but the changes are pretty trivial; see
the affected contrib modules for examples of the minimum change needed.
(Most compilers should give pointer-type-mismatch warnings for uncorrected
code.)
There's also a change in the API of ExplainOneQuery_hook, to pass through
cursorOptions instead of expecting hook functions to know what to pick.
This is needed because of the DECLARE CURSOR changes, but really should
have been done in 9.6; it's unlikely that any extant hook functions
know about using CURSOR_OPT_PARALLEL_OK.
Finally, teach gram.y to save statement boundary locations in RawStmt
nodes, and pass those through to Query and PlannedStmt nodes. This allows
more intelligent handling of cases where a source query string contains
multiple statements. This patch doesn't actually do anything with the
information, but a follow-on patch will. (Passing this information through
cleanly is the true motivation for these changes; while I think this is all
good cleanup, it's unlikely we'd have bothered without this end goal.)
catversion bump because addition of location fields to struct Query
affects stored rules.
This patch is by me, but it owes a good deal to Fabien Coelho who did
a lot of preliminary work on the problem, and also reviewed the patch.
Discussion: https://postgr.es/m/alpine.DEB.2.20.1612200926310.29821@lancre
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I found that half a dozen (nearly 5%) of our AllocSetContextCreate calls
had typos in the context-sizing parameters. While none of these led to
especially significant problems, they did create minor inefficiencies,
and it's now clear that expecting people to copy-and-paste those calls
accurately is not a great idea. Let's reduce the risk of future errors
by introducing single macros that encapsulate the common use-cases.
Three such macros are enough to cover all but two special-purpose contexts;
those two calls can be left as-is, I think.
While this patch doesn't in itself improve matters for third-party
extensions, it doesn't break anything for them either, and they can
gradually adopt the simplified notation over time.
In passing, change TopMemoryContext to use the default allocation
parameters. Formerly it could only be extended 8K at a time. That was
probably reasonable when this code was written; but nowadays we create
many more contexts than we did then, so that it's not unusual to have a
couple hundred K in TopMemoryContext, even without considering various
dubious code that sticks other things there. There seems no good reason
not to let it use growing blocks like most other contexts.
Back-patch to 9.6, mostly because that's still close enough to HEAD that
it's easy to do so, and keeping the branches in sync can be expected to
avoid some future back-patching pain. The bugs fixed by these changes
don't seem to be significant enough to justify fixing them further back.
Discussion: <[email protected]>
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Discussion of commit 3e2f3c2e4 exposed a problem that is of longer
standing: since we don't detoast data while sticking it into a portal's
holdStore for PORTAL_ONE_RETURNING and PORTAL_UTIL_SELECT queries, and we
release the query's snapshot as soon as we're done loading the holdStore,
later readout of the holdStore can do TOAST fetches against data that can
no longer be seen by any of the session's live snapshots. This means that
a concurrent VACUUM could remove the TOAST data before we can fetch it.
Commit 3e2f3c2e4 exposed the problem by showing that sometimes we had *no*
live snapshots while fetching TOAST data, but we'd be at risk anyway.
I believe this code was all right when written, because our management of a
session's exposed xmin was such that the TOAST references were safe until
end of transaction. But that's no longer true now that we can advance or
clear our PGXACT.xmin intra-transaction.
To fix, copy the query's snapshot during FillPortalStore() and save it in
the Portal; release it only when the portal is dropped. This essentially
implements a policy that we must hold a relevant snapshot whenever we
access potentially-toasted data. We had already come to that conclusion
in other places, cf commits 08e261cbc94ce9a7 and ec543db77b6b72f2.
I'd have liked to add a regression test case for this, but I didn't see
a way to make one that's not unreasonably bloated; it seems to require
returning a toasted value to the client, and those will be big.
In passing, improve PortalRunUtility() so that it positively verifies
that its ending PopActiveSnapshot() call will pop the expected snapshot,
removing a rather shaky assumption about which utility commands might
do their own PopActiveSnapshot(). There's no known bug here, but now
that we're actively referencing the snapshot it's almost free to make
this code a bit more bulletproof.
We might want to consider back-patching something like this into older
branches, but it would be prudent to let it prove itself more in HEAD
beforehand.
Discussion: <[email protected]>
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Reviewed by Tom Lane and Robert Haas.
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Backpatch certain files through 9.1
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Formerly, we treated only portals created in the current subtransaction as
having failed during subtransaction abort. However, if the error occurred
while running a portal created in an outer subtransaction (ie, a cursor
declared before the last savepoint), that has to be considered broken too.
To allow reliable detection of which ones those are, add a bookkeeping
field to struct Portal that tracks the innermost subtransaction in which
each portal has actually been executed. (Without this, we'd end up
failing portals containing functions that had called the subtransaction,
thereby breaking plpgsql exception blocks completely.)
In addition, when we fail an outer-subtransaction Portal, transfer its
resources into the subtransaction's resource owner, so that they're
released early in cleanup of the subxact. This fixes a problem reported by
Jim Nasby in which a function executed in an outer-subtransaction cursor
could cause an Assert failure or crash by referencing a relation created
within the inner subtransaction.
The proximate cause of the Assert failure is that AtEOSubXact_RelationCache
assumed it could blow away a relcache entry without first checking that the
entry had zero refcount. That was a bad idea on its own terms, so add such
a check there, and to the similar coding in AtEOXact_RelationCache. This
provides an independent safety measure in case there are still ways to
provoke the situation despite the Portal-level changes.
This has been broken since subtransactions were invented, so back-patch
to all supported branches.
Tom Lane and Michael Paquier
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Backpatch certain files through 9.0
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This includes removing tabs after periods in C comments, which was
applied to back branches, so this change should not effect backpatching.
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