pgoutput caches the attribute map of a relation, that is free()'d only
when validating a RelationSyncEntry. However, this code path is not
taken when calling any of the SQL functions able to do some logical
decoding, like pg_logical_slot_{get,peek}_changes(), leaking some memory
into CacheMemoryContext on repeated calls.
To address this, a relation's attribute map is allocated in
PGOutputData's cachectx, free()'d at the end of the execution of these
SQL functions when logical decoding ends. This is available down to 15.
v13 and v14 have a similar leak, which will be dealt with later.
Reported-by: Masahiko Sawada
Author: Vignesh C
Reviewed-by: Hou Zhijie
Discussion: https://postgr.es/m/CAD21AoDkAhQVSukOfH3_reuF-j4EU0-HxMqU3dU+bSTxsqT14Q@mail.gmail.com
Discussion: https://postgr.es/m/CALDaNm1hewNAsZ_e6FF52a=9drmkRJxtEPrzCB6-9mkJyeBBqA@mail.gmail.com
Backpatch-through: 15
Trying to clean up the code a bit while we're working on these files
for the reentrant scanner/pure parser patches. This cleanup only
touches the code sections after the second '%%' in each file, via a
manually-supervised and locally hacked up pgindent.
Use the flex %option reentrant and the bison option %pure-parser to
make the generated scanner and parser pure, reentrant, and
thread-safe.
Make the generated scanner use palloc() etc. instead of malloc() etc.
Previously, we only used palloc() for the buffer, but flex would still
use malloc() for its internal structures. Now, all the memory is
under palloc() control.
Simplify flex scan buffer management: Instead of constructing the
buffer from pieces and then using yy_scan_buffer(), we can just use
yy_scan_string(), which does the same thing internally.
The previous code was necessary because we allocated the buffer with
palloc() and the rest of the state was handled by malloc(). But this
is no longer the case; everything is under palloc() now.
Use flex yyextra to handle context information, instead of global
variables. This complements the other changes to make the scanner
reentrant.
Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-by: Andreas Karlsson <andreas@proxel.se>
Discussion: https://www.postgresql.org/message-id/flat/eb6faeac-2a8a-4b69-9189-c33c520e5b7b@eisentraut.org
Use the flex %option reentrant and the bison option %pure-parser to
make the generated scanner and parser pure, reentrant, and
thread-safe.
Make the generated scanner use palloc() etc. instead of malloc() etc.
Previously, we only used palloc() for the buffer, but flex would still
use malloc() for its internal structures. As a result, there could be
some small memory leaks in case of uncaught errors. Now, all the
memory is under palloc() control, so there are no more such issues.
Simplify flex scan buffer management: Instead of constructing the
buffer from pieces and then using yy_scan_buffer(), we can just use
yy_scan_string(), which does the same thing internally.
The previous code was necessary because we allocated the buffer with
palloc() and the rest of the state was handled by malloc(). But this
is no longer the case; everything is under palloc() now.
Use flex yyextra to handle context information, instead of global
variables. This complements the other changes to make the scanner
reentrant.
Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Co-authored-by: Andreas Karlsson <andreas@proxel.se>
Reviewed-by: Andreas Karlsson <andreas@proxel.se>
Discussion: https://www.postgresql.org/message-id/flat/eb6faeac-2a8a-4b69-9189-c33c520e5b7b@eisentraut.org
In get_database_list() and get_subscription_list(), the
GetTransactionSnapshot() call is not required because the catalog
table scans use the catalog snapshot, which is held until the end of
the scan. See table_beginscan_catalog(), which calls
RegisterSnapshot(GetCatalogSnapshot(relid)).
In InitPostgres, it's a little less obvious that it's not required,
but still true I believe. All the catalog lookups in InitPostgres()
also use the catalog snapshot, and the looked up values are copied
while still holding the snapshot.
Furthermore, as the removed FIXME comments said, calling
GetTransactionSnapshot() didn't really prevent MyProc->xmin from being
reset anyway.
Discussion: https://www.postgresql.org/message-id/7c56f180-b9e1-481e-8c1d-efa63de3ecbb@iki.fi
This used to say "nsubxcnt isn't decreased when subtransactions
abort", but there's no variable called nsubxcnt. Commit 8548ddc61b
changed it to "subxcnt", among other typo fixes, but that was wrong
too: the comment actually talks about txn->nsubtxns. That's the field
that's incremented but never decremented and is used for the
allocation earlier in the function.
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
IsIndexUsableForReplicaIdentityFull() described a number of conditions
that a suitable index has to fulfill. But not all of these were
actually checked in the code. Instead, it appeared to rely on
get_equal_strategy_number() to filter out any indexes that are not
btree or hash. As we look to generalize index AM capabilities, this
would possibly break if we added additional support in
get_equal_strategy_number(). Instead, write out code to check for the
required capabilities explicitly. This shouldn't change any behaviors
at the moment.
Reviewed-by: Paul Jungwirth <pj@illuminatedcomputing.com>
Reviewed-by: vignesh C <vignesh21@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CA+renyUApHgSZF9-nd-a0+OPGharLQLO=mDHcY4_qQ0+noCUVg@mail.gmail.com
get_equal_strategy_number_for_am() gets the equal strategy number for
an AM. This currently only supports btree and hash. In the more
general case, this also depends on the operator class (see for example
GistTranslateStratnum()). To support that, replace this function with
get_equal_strategy_number() that takes an opclass and derives it from
there. (This function already existed before as a static function, so
the signature is kept for simplicity.)
This patch is only a refactoring, it doesn't add support for other
index AMs such as gist. This will be done separately.
Reviewed-by: Paul Jungwirth <pj@illuminatedcomputing.com>
Reviewed-by: vignesh C <vignesh21@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CA+renyUApHgSZF9-nd-a0+OPGharLQLO=mDHcY4_qQ0+noCUVg@mail.gmail.com
The pgoutput module caches publication names in a list and frees it upon
invalidation. However, the code forgot to free the actual publication
names within the list elements, as publication names are pstrdup()'d in
GetPublication(). This would cause memory to leak in
CacheMemoryContext, bloating it over time as this context is not
cleaned.
This is a problem for WAL senders running for a long time, as an
accumulation of invalidation requests would bloat its cache memory
usage. A second case, where this leak is easier to see, involves a
backend calling SQL functions like pg_logical_slot_{get,peek}_changes()
which create a new decoding context with each execution. More
publications create more bloat.
To address this, this commit adds a new memory context within the
logical decoding context and resets it each time the publication names
cache is invalidated, based on a suggestion from Amit Kapila. This
ensures that the lifespan of the publication names aligns with that of
the logical decoding context.
This solution changes PGOutputData, which is fine for HEAD but it could
cause an ABI breakage in stable branches as the structure size would
change, so these are left out for now.
Analyzed-by: Michael Paquier, Jeff Davis
Author: Zhijie Hou
Reviewed-by: Michael Paquier, Masahiko Sawada, Euler Taveira
Discussion: https://postgr.es/m/Z0khf9EVMVLOc_YY@paquier.xyz
The validate_sync_standby_slots subroutine requires an LWLock, so it
cannot run in processes without PGPROC; skip it there to avoid a crash.
This replaces the current test for ReplicationSlotCtl being not null,
which appears to be a solution for the same problem but less general.
I also rewrote a related comment that mentioned ReplicationSlotCtl in
StandbySlotsHaveCaughtup.
This code came in with commit bf279ddd1c28; backpatch to 17.
Reported-by: Gabriele Bartolini <gabriele.bartolini@enterprisedb.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Reviewed-by: Zhijie Hou <houzj.fnst@fujitsu.com>
Discussion: https://postgr.es/m/202411281216.sutbxtr6idnn@alvherre.pgsql
They were all missing punctuation, one was missing initial capital.
Per our message style guidelines.
No backpatch, to avoid breaking existing translations.
Currently, logical replication produces a generic error message when
targeting a subscriber-side table column that is either missing or
generated. The error message can be misleading for generated columns.
This patch introduces a specific error message to clarify the issue when
generated columns are involved.
Author: Shubham Khanna
Reviewed-by: Peter Smith, Vignesh C, Amit Kapila
Discussion: https://postgr.es/m/CAHv8RjJBvYtqU7OAofBizOmQOK2Q8h+w9v2_cQWxT_gO7er3Aw@mail.gmail.com
RelationSyncCache, the hash table in charge of tracking the relation
schemas sent through pgoutput, was forgetting to free the TupleDesc
associated to the two slots used to store the new and old tuples,
causing some memory to be leaked each time a relation is invalidated
when the slots of an existing relation entry are cleaned up.
This is rather hard to notice as the bloat is pretty minimal, but a
long-running WAL sender would be in trouble over time depending on the
workload. sysbench has proved to be pretty good at showing the problem,
coupled with some memory monitoring of the WAL sender.
Issue introduced in 52e4f0cd47, that has added row filters for tables
logically replicated.
Author: Boyu Yang
Reviewed-by: Michael Paquier, Hou Zhijie
Discussion: https://postgr.es/m/DM3PR84MB3442E14B340E553313B5C816E3252@DM3PR84MB3442.NAMPRD84.PROD.OUTLOOK.COM
Backpatch-through: 15
Previously LogicalIncreaseRestartDecodingForSlot() accidentally
accepted any LSN as the candidate_lsn and candidate_valid after the
restart_lsn of the replication slot was updated, so it potentially
caused the restart_lsn to move backwards.
A scenario where this could happen in logical replication is: after a
logical replication restart, based on previous candidate_lsn and
candidate_valid values in memory, the restart_lsn advances upon
receiving a subscriber acknowledgment. Then, logical decoding restarts
from an older point, setting candidate_lsn and candidate_valid based
on an old RUNNING_XACTS record. Subsequent subscriber acknowledgments
then update the restart_lsn to an LSN older than the current value.
In the reported case, after WAL files were removed by a checkpoint,
the retreated restart_lsn prevented logical replication from
restarting due to missing WAL segments.
This change essentially modifies the 'if' condition to 'else if'
condition within the function. The previous code had an asymmetry in
this regard compared to LogicalIncreaseXminForSlot(), which does
almost the same thing for different fields.
The WAL removal issue was reported by Hubert Depesz Lubaczewski.
Backpatch to all supported versions, since the bug exists since 9.4
where logical decoding was introduced.
Reviewed-by: Tomas Vondra, Ashutosh Bapat, Amit Kapila
Discussion: https://postgr.es/m/Yz2hivgyjS1RfMKs%40depesz.com
Discussion: https://postgr.es/m/85fff40e-148b-4e86-b921-b4b846289132%40vondra.me
Backpatch-through: 13
We now create contype='n' pg_constraint rows for not-null constraints on
user tables. Only one such constraint is allowed for a column.
We propagate these constraints to other tables during operations such as
adding inheritance relationships, creating and attaching partitions and
creating tables LIKE other tables. These related constraints mostly
follow the well-known rules of conislocal and coninhcount that we have
for CHECK constraints, with some adaptations: for example, as opposed to
CHECK constraints, we don't match not-null ones by name when descending
a hierarchy to alter or remove it, instead matching by the name of the
column that they apply to. This means we don't require the constraint
names to be identical across a hierarchy.
The inheritance status of these constraints can be controlled: now we
can be sure that if a parent table has one, then all children will have
it as well. They can optionally be marked NO INHERIT, and then children
are free not to have one. (There's currently no support for altering a
NO INHERIT constraint into inheriting down the hierarchy, but that's a
desirable future feature.)
This also opens the door for having these constraints be marked NOT
VALID, as well as allowing UNIQUE+NOT NULL to be used for functional
dependency determination, as envisioned by commit e49ae8d3bc. It's
likely possible to allow DEFERRABLE constraints as followup work, as
well.
psql shows these constraints in \d+, though we may want to reconsider if
this turns out to be too noisy. Earlier versions of this patch hid
constraints that were on the same columns of the primary key, but I'm
not sure that that's very useful. If clutter is a problem, we might be
better off inventing a new \d++ command and not showing the constraints
in \d+.
For now, we omit these constraints on system catalog columns, because
they're unlikely to achieve anything.
The main difference to the previous attempt at this (b0e96f3119) is
that we now require that such a constraint always exists when a primary
key is in the column; we didn't require this previously which had a
number of unpalatable consequences. With this requirement, the code is
easier to reason about. For example:
- We no longer have "throwaway constraints" during pg_dump. We needed
those for the case where a table had a PK without a not-null
underneath, to prevent a slow scan of the data during restore of the
PK creation, which was particularly problematic for pg_upgrade.
- We no longer have to cope with attnotnull being set spuriously in
case a primary key is dropped indirectly (e.g., via DROP COLUMN).
Some bits of code in this patch were authored by Jian He.
Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Author: Bernd Helmle <mailings@oopsware.de>
Reviewed-by: 何建 (jian he) <jian.universality@gmail.com>
Reviewed-by: 王刚 (Tender Wang) <tndrwang@gmail.com>
Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>
Reviewed-by: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Reviewed-by: Dean Rasheed <dean.a.rasheed@gmail.com>
Discussion: https://postgr.es/m/202408310358.sdhumtyuy2ht@alvherre.pgsql
This patch builds on the work done in commit 745217a051 by enabling the
replication of generated columns alongside regular column changes through
a new publication parameter: publish_generated_columns.
Example usage:
CREATE PUBLICATION pub1 FOR TABLE tab_gencol WITH (publish_generated_columns = true);
The column list takes precedence. If the generated columns are specified
in the column list, they will be replicated even if
'publish_generated_columns' is set to false. Conversely, if generated
columns are not included in the column list (assuming the user specifies a
column list), they will not be replicated even if
'publish_generated_columns' is true.
Author: Vignesh C, Shubham Khanna
Reviewed-by: Peter Smith, Amit Kapila, Hayato Kuroda, Shlok Kyal, Ajin Cherian, Hou Zhijie, Masahiko Sawada
Discussion: https://postgr.es/m/B80D17B2-2C8E-4C7D-87F2-E5B4BE3C069E@gmail.com
This commit allows logical replication to publish and replicate generated
columns when explicitly listed in the column list. We also ensured that
the generated columns were copied during the initial tablesync when they
were published.
We will allow to replicate generated columns even when they are not
specified in the column list (via a new publication option) in a separate
commit.
The motivation of this work is to allow replication for cases where the
client doesn't have generated columns. For example, the case where one is
trying to replicate data from Postgres to the non-Postgres database.
Author: Shubham Khanna, Vignesh C, Hou Zhijie
Reviewed-by: Peter Smith, Hayato Kuroda, Shlok Kyal, Amit Kapila
Discussion: https://postgr.es/m/B80D17B2-2C8E-4C7D-87F2-E5B4BE3C069E@gmail.com
The inplace update survives ROLLBACK. The inval didn't, so another
backend's DDL could then update the row without incorporating the
inplace update. In the test this fixes, a mix of CREATE INDEX and ALTER
TABLE resulted in a table with an index, yet relhasindex=f. That is a
source of index corruption. Back-patch to v12 (all supported versions).
The back branch versions don't change WAL, because those branches just
added end-of-recovery SIResetAll(). All branches change the ABI of
extern function PrepareToInvalidateCacheTuple(). No PGXN extension
calls that, and there's no apparent use case in extensions.
Reviewed by Nitin Motiani and (in earlier versions) Andres Freund.
Discussion: https://postgr.es/m/20240523000548.58.nmisch@google.com
The existing get_publications_str() is renamed to GetPublicationsStr()
and is moved to pg_subscription.c, so as it is possible to reuse it at
two locations of the tablesync code where the same logic was duplicated.
fetch_remote_table_info() was doing two List->StringInfo conversions
when dealing with a server of version 15 or newer. The conversion
happens only once now.
This refactoring leads to less code overall.
Author: Peter Smith
Reviewed-by: Michael Paquier, Masahiko Sawada
Discussion: https://postgr.es/m/CAHut+PtJMk4bKXqtpvqVy9ckknCgK9P6=FeG8zHF=6+Em_Snpw@mail.gmail.com
Commit a4ccc1cef introduced the Generation Context and modified the
logical decoding process to use a Generation Context with a fixed
block size of 8MB for storing tuple data decoded during logical
decoding (i.e., rb->tup_context). Several reports have indicated that
the logical decoding process can be terminated due to
out-of-memory (OOM) situations caused by excessive memory usage in
rb->tup_context.
This issue can occur when decoding a workload involving several
concurrent transactions, including a long-running transaction that
modifies tuples. By design, the Generation Context does not free a
memory block until all chunks within that block are
released. Consequently, if tuples modified by the long-running
transaction are stored across multiple memory blocks, these blocks
remain allocated until the long-running transaction completes, leading
to substantial memory fragmentation. The memory usage during logical
decoding, tracked by rb->size, does not account for memory
fragmentation, resulting in potentially much higher memory consumption
than the value of the logical_decoding_work_mem parameter.
Various improvement strategies were discussed in the relevant
thread. This change reduces the block size of the Generation Context
used in rb->tup_context from 8MB to 8kB. This modification
significantly decreases the likelihood of substantial memory
fragmentation occurring and is relatively straightforward to
backport. Performance testing across multiple platforms has confirmed
that this change will not introduce any performance degradation that
would impact actual operation.
Backport to all supported branches.
Reported-by: Alex Richman, Michael Guissine, Avi Weinberg
Reviewed-by: Amit Kapila, Fujii Masao, David Rowley
Tested-by: Hayato Kuroda, Shlok Kyal
Discussion: https://postgr.es/m/CAD21AoBTY1LATZUmvSXEssvq07qDZufV4AF-OHh9VD2pC0VY2A%40mail.gmail.com
Backpatch-through: 12
This module provides SQL functions that allow to inspect logical
decoding components.
It currently allows to inspect the contents of serialized logical
snapshots of a running database cluster, which is useful for debugging
or educational purposes.
Author: Bertrand Drouvot
Reviewed-by: Amit Kapila, Shveta Malik, Peter Smith, Peter Eisentraut
Reviewed-by: David G. Johnston
Discussion: https://postgr.es/m/ZscuZ92uGh3wm4tW%40ip-10-97-1-34.eu-west-3.compute.internal
This commit moves the definitions of the SnapBuild and SnapBuildOnDisk
structs, related to logical snapshots, to the snapshot_internal.h
file. This change allows external tools, such as
pg_logicalinspect (with an upcoming patch), to access and utilize the
contents of logical snapshots.
Author: Bertrand Drouvot
Reviewed-by: Amit Kapila, Shveta Malik, Peter Smith
Discussion: https://postgr.es/m/ZscuZ92uGh3wm4tW%40ip-10-97-1-34.eu-west-3.compute.internal
The first part of the assertion verifying that the passed index must be PK
or RI was incorrectly passing index relation instead of heap relation in
GetRelationIdentityOrPK(). The assertion was not failing because the
second part of the assertion which needs to be performed only when remote
relation has REPLICA_IDENTITY_FULL set was also incorrect.
The change is not backpatched because the current coding doesn't lead to
any failure.
Reported-by: Dilip Kumar
Author: Amit Kapila
Reviewed-by: Vignesh C
Discussion: https://postgr.es/m/CAFiTN-tmguaT1DXbCC+ZomZg-oZLmU6BPhr0po7akQSG6vNJrg@mail.gmail.com
This commit adds columns in view pg_stat_subscription_stats to show the
number of times a particular conflict type has occurred during the
application of logical replication changes. The following columns are
added:
confl_insert_exists:
Number of times a row insertion violated a NOT DEFERRABLE unique
constraint.
confl_update_origin_differs:
Number of times an update was performed on a row that was
previously modified by another origin.
confl_update_exists:
Number of times that the updated value of a row violates a
NOT DEFERRABLE unique constraint.
confl_update_missing:
Number of times that the tuple to be updated is missing.
confl_delete_origin_differs:
Number of times a delete was performed on a row that was
previously modified by another origin.
confl_delete_missing:
Number of times that the tuple to be deleted is missing.
The update_origin_differs and delete_origin_differs conflicts can be
detected only when track_commit_timestamp is enabled.
Author: Hou Zhijie
Reviewed-by: Shveta Malik, Peter Smith, Anit Kapila
Discussion: https://postgr.es/m/OS0PR01MB57160A07BD575773045FC214948F2@OS0PR01MB5716.jpnprd01.prod.outlook.com
This commit replaces most of the hardcoded values of "pg_replslot" by a
new PG_REPLSLOT_DIR #define. This makes the style more consistent with
the existing PG_STAT_TMP_DIR, for example. More places will follow a
similar change.
Author: Bertrand Drouvot
Reviewed-by: Ashutosh Bapat, Yugo Nagata, Michael Paquier
Discussion: https://postgr.es/m/ZryVvjqS9SnV1GPP@ip-10-97-1-34.eu-west-3.compute.internal
The conflict types 'update_differ' and 'delete_differ' indicate that a row
to be modified was previously altered by another origin. Rename those to
'update_origin_differs' and 'delete_origin_differs' to clarify their
meaning.
Author: Hou Zhijie
Reviewed-by: Shveta Malik, Peter Smith
Discussion: https://postgr.es/m/CAA4eK1+HEKwG_UYt4Zvwh5o_HoCKCjEGesRjJX38xAH3OxuuYA@mail.gmail.com
Commit 5bec1d6bc5 changed the memory usage updates of the
ReorderBufferTXN to zero all at once by subtracting txn->size, rather
than updating it for each change. However, if TOAST reconstruction
data remained in the transaction when freeing it, there were cases
where it further subtracted the memory counter from zero, resulting in
an assertion failure.
This change calculates the memory size for each change and updates the
memory usage to precisely the amount that has been freed.
Backpatch to v17, where this was introducd.
Reviewed-by: Amit Kapila, Shlok Kyal
Discussion: https://postgr.es/m/CAD21AoAqkNUvicgKPT_dXzNoOwpPkVTg0QPPxEcWmzT0moCJ1g%40mail.gmail.com
Backpatch-through: 17
We advance origin progress during abort on successful streaming and
application of ROLLBACK in parallel streaming mode. But the origin
shouldn't be advanced during an error or unsuccessful apply due to
shutdown. Otherwise, it will result in a transaction loss as such a
transaction won't be sent again by the server.
Reported-by: Hou Zhijie
Author: Hayato Kuroda and Shveta Malik
Reviewed-by: Amit Kapila
Backpatch-through: 16
Discussion: https://postgr.es/m/TYAPR01MB5692FAC23BE40C69DA8ED4AFF5B92@TYAPR01MB5692.jpnprd01.prod.outlook.com