To improve the usability of logical replication examples, we need to
enable bulk copy-pasting of DML/DDL series.
Currently, output command tags and prompts disrupt this workflow. While
prompts are typically removed, converting them to comments is acceptable
here, given the multi-server context.
Additionally, ensure all examples containing operators like < and > are
wrapped in CDATA blocks to guarantee correct rendering and consistency
with other places.
Author: David G. Johnston <david.g.johnston@gmail.com>
Reviewed-by: Peter Smith <smithpb2250@gmail.com>
Discussion: https://postgr.es/m/CAKFQuwbhbL1uaDTuo9shmo1rA-fX6XGotR7qZQ7rd-ia5ZDoQA@mail.gmail.com
Introduce a new conflict type, multiple_unique_conflicts, to handle cases
where an incoming row during logical replication violates multiple UNIQUE
constraints.
Previously, the apply worker detected and reported only the first
encountered key conflict (insert_exists/update_exists), causing repeated
failures as each constraint violation needs to be handled one by one
making the process slow and error-prone.
With this patch, the apply worker checks all unique constraints upfront
once the first key conflict is detected and reports
multiple_unique_conflicts if multiple violations exist. This allows users
to resolve all conflicts at once by deleting all conflicting tuples rather
than dealing with them individually or skipping the transaction.
In the future, this will also allow us to specify different resolution
handlers for such a conflict type.
Add the stats for this conflict type in pg_stat_subscription_stats.
Author: Nisha Moond <nisha.moond412@gmail.com>
Author: Zhijie Hou <houzj.fnst@fujitsu.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Reviewed-by: Peter Smith <smithpb2250@gmail.com>
Reviewed-by: Dilip Kumar <dilipbalaut@gmail.com>
Discussion: https://postgr.es/m/CABdArM7FW-_dnthGkg2s0fy1HhUB8C3ELA0gZX1kkbs1ZZoV3Q@mail.gmail.com
This commit introduces a new GUC option max_active_replication_origins
to control the maximum number of active replication
origins. Previously, this was controlled by
'max_replication_slots'. Having a separate GUC option provides better
flexibility for setting up subscribers, as they may not require
replication slots (for cascading replication) but always require
replication origins.
Author: Euler Taveira <euler@eulerto.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Reviewed-by: vignesh C <vignesh21@gmail.com>
Discussion: https://postgr.es/m/b81db436-8262-4575-b7c4-bc0c1551000b@app.fastmail.com
This commit introduces idle_replication_slot_timeout GUC that allows
inactive slots to be invalidated at the time of checkpoint. Because
checkpoints happen checkpoint_timeout intervals, there can be some lag
between when the idle_replication_slot_timeout was exceeded and when the
slot invalidation is triggered at the next checkpoint. To avoid such lags,
users can force a checkpoint to promptly invalidate inactive slots.
Note that the idle timeout invalidation mechanism is not applicable for
slots that do not reserve WAL or for slots on the standby server that are
synced from the primary server (i.e., standby slots having 'synced' field
'true'). Synced slots are always considered to be inactive because they
don't perform logical decoding to produce changes.
The slots can become inactive for a long period if a subscriber is down
due to a system error or inaccessible because of network issues. If such a
situation persists, it might be more practical to recreate the subscriber
rather than attempt to recover the node and wait for it to catch up which
could be time-consuming.
Then, external tools could create replication slots (e.g., for migrations
or upgrades) that may fail to remove them if an error occurs, leaving
behind unused slots that take up space and resources. Manually cleaning
them up can be tedious and error-prone, and without intervention, these
lingering slots can cause unnecessary WAL retention and system bloat.
As the duration of idle_replication_slot_timeout is in minutes, any test
using that would be time-consuming. We are planning to commit a follow up
patch for tests by using the injection point framework.
Author: Nisha Moond <nisha.moond412@gmail.com>
Author: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Reviewed-by: Peter Smith <smithpb2250@gmail.com>
Reviewed-by: Hayato Kuroda <kuroda.hayato@fujitsu.com>
Reviewed-by: Vignesh C <vignesh21@gmail.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Reviewed-by: Hou Zhijie <houzj.fnst@fujitsu.com>
Reviewed-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Discussion: https://postgr.es/m/CALj2ACW4aUe-_uFQOjdWCEN-xXoLGhmvRFnL8SNw_TZ5nJe+aw@mail.gmail.com
Discussion: https://postgr.es/m/OS0PR01MB5716C131A7D80DAE8CB9E88794FC2@OS0PR01MB5716.jpnprd01.prod.outlook.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
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
This patch provides the additional logging information in the following
conflict scenarios while applying changes:
insert_exists: Inserting a row that violates a NOT DEFERRABLE unique constraint.
update_differ: Updating a row that was previously modified by another origin.
update_exists: The updated row value violates a NOT DEFERRABLE unique constraint.
update_missing: The tuple to be updated is missing.
delete_differ: Deleting a row that was previously modified by another origin.
delete_missing: The tuple to be deleted is missing.
For insert_exists and update_exists conflicts, the log can include the origin
and commit timestamp details of the conflicting key with track_commit_timestamp
enabled.
update_differ and delete_differ conflicts can only be detected when
track_commit_timestamp is enabled on the subscriber.
We do not offer additional logging for exclusion constraint violations because
these constraints can specify rules that are more complex than simple equality
checks. Resolving such conflicts won't be straightforward. This area can be
further enhanced if required.
Author: Hou Zhijie
Reviewed-by: Shveta Malik, Amit Kapila, Nisha Moond, Hayato Kuroda, Dilip Kumar
Discussion: https://postgr.es/m/OS0PR01MB5716352552DFADB8E9AD1D8994C92@OS0PR01MB5716.jpnprd01.prod.outlook.com
The standby_slot_names GUC allows the specification of physical standby
slots that must be synchronized before the logical walsenders associated
with logical failover slots. However, for this purpose, the GUC name is
too generic.
Author: Hou Zhijie
Reviewed-by: Bertrand Drouvot, Masahiko Sawada
Backpatch-through: 17
Discussion: https://postgr.es/m/ZnWeUgdHong93fQN@momjian.us
Commit 536f410111 added links in the ALTER SUBSCRIPTION command page. The
link names used were slightly different from what other logical
replication commands like CREATE SUBSCRIPTION/PUBLICATION have but were
consistent with other docs. This patch changes the link names for all the
parameters to have 'params' word in the CREATE SUBSCRIPTION/PUBLICATION
pages.
Author: Peter Smith
Reviewed-by: Amit Kapila
Discussion: http://postgr.es/m/CAHut%2BPu2S4RdzYKR7H5_E7QYWyq5hB0hL4EFrYbP91Qso62jeg%40mail.gmail.com
Commit 89e46da5e5 allowed using BTREE indexes that are neither
PRIMARY KEY nor REPLICA IDENTITY on the subscriber during apply of
update/delete. This patch extends that functionality to also allow HASH
indexes.
We explored supporting other index access methods as well but they don't
have a fixed strategy for equality operation which is required by the
current infrastructure in logical replication to scan the indexes.
Author: Kuroda Hayato
Reviewed-by: Peter Smith, Onder Kalaci, Amit Kapila
Discussion: https://postgr.es/m/TYAPR01MB58669D7414E59664E17A5827F522A@TYAPR01MB5866.jpnprd01.prod.outlook.com
Commit 89e46da5e allowed REPLICA IDENTITY FULL tables to use an index
on the subscriber during apply of update/delete. This commit clarifies
in the documentation that the leftmost field of candidate indexes must
be a column (not an expression) that references the published relation
column.
The source code comments are also updated accordingly.
Reviewed-by: Peter Smith, Amit Kapila
Discussion: https://postgr.es/m/CAD21AoDJjffEvUFKXT27Q5U8-UU9JHv4rrJ9Ke8Zkc5UPWHLvA@mail.gmail.com
Backpatch-through: 16
By default, triggers and rules do not fire on a logical replication
subscriber based on the "session_replication_role" GUC being set to
"replica". However, the docs in the logical replication section assumed
that the reader understood how this GUC worked. This modifies the docs to
be more explicit and links back to the GUC itself.
Author: Jonathan Katz, Peter Smith
Reviewed-by: Vignesh C, Euler Taveira
Backpatch-through: 11
Discussion: https://postgr.es/m/5bb2c9a2-499f-e1a2-6e33-5ce96b35cc4a@postgresql.org
This option is normally false, but can be set to true to obtain
the legacy behavior where the subscription runs with the permissions
of the subscription owner rather than the permissions of the
table owner. The advantages of this mode are (1) it doesn't require
that the subscription owner have permission to SET ROLE to each
table owner and (2) since no role switching occurs, the
SECURITY_RESTRICTED_OPERATION restrictions do not apply.
On the downside, it allows any table owner to easily usurp
the privileges of the subscription owner - basically, to take
over their account. Because that's generally quite undesirable,
we don't make this mode the default, but we do make it available,
just in case the new behavior causes too many problems for someone.
Discussion: http://postgr.es/m/CA+TgmoZ-WEeG6Z14AfH7KhmpX2eFh+tZ0z+vf0=eMDdbda269g@mail.gmail.com
Up until now, logical replication actions have been performed as the
subscription owner, who will generally be a superuser. Commit
cec57b1a0f documented hazards
associated with that situation, namely, that any user who owns a
table on the subscriber side could assume the privileges of the
subscription owner by attaching a trigger, expression index, or
some other kind of executable code to it. As a remedy, it suggested
not creating configurations where users who are not fully trusted
own tables on the subscriber.
Although that will work, it basically precludes using logical
replication in the way that people typically want to use it,
namely, to replicate a database from one node to another
without necessarily having any restrictions on which database
users can own tables. So, instead, change logical replication to
execute INSERT, UPDATE, DELETE, and TRUNCATE operations as the
table owner when they are replicated.
Since this involves switching the active user frequently within
a session that is authenticated as the subscription user, also
impose SECURITY_RESTRICTED_OPERATION restrictions on logical
replication code. As an exception, if the table owner can SET
ROLE to the subscription owner, these restrictions have no
security value, so don't impose them in that case.
Subscription owners are now required to have the ability to
SET ROLE to every role that owns a table that the subscription
is replicating. If they don't, replication will fail. Superusers,
who normally own subscriptions, satisfy this property by default.
Non-superusers users who own subscriptions will need to be
granted the roles that own relevant tables.
Patch by me, reviewed (but not necessarily in its entirety) by
Jelte Fennema, Jeff Davis, and Noah Misch.
Discussion: http://postgr.es/m/CA+TgmoaSCkg9ww9oppPqqs+9RVqCexYCE6Aq=UsYPfnOoDeFkw@mail.gmail.com
Commit ecb696527c added an XML ID attribute to one varlistentry in
create_subscription.sgml. Following 78ee60ed84, this commit adds XML ID
attributes to all varlistentries in create_subscription.sgml.
Additionally, links are added to refer to the subscription options,
enhancing the readability of documents.
Author: Kuroda Hayato
Reviewed-by: Peter Smith, Amit Kapila
Discussion: https://postgr.es/m/TYAPR01MB58667AE04D291924671E2051F5879@TYAPR01MB5866.jpnprd01.prod.outlook.com
This patch allows copying tables in the binary format during table
synchronization when the binary option for a subscription is enabled.
Previously, tables are copied in text format even if the subscription is
created with the binary option enabled. Copying tables in binary format
may reduce the time spent depending on column types.
A binary copy for initial table synchronization is supported only when
both publisher and subscriber are v16 or later.
Author: Melih Mutlu
Reviewed-by: Peter Smith, Shi yu, Euler Taveira, Vignesh C, Kuroda Hayato, Osumi Takamichi, Bharath Rupireddy, Hou Zhijie
Discussion: https://postgr.es/m/CAGPVpCQvAziCLknEnygY0v1-KBtg%2BOm-9JHJYZOnNPKFJPompw%40mail.gmail.com
Using REPLICA IDENTITY FULL on the publisher can lead to a full table scan
per tuple change on the subscription when REPLICA IDENTITY or PK index is
not available. This makes REPLICA IDENTITY FULL impractical to use apart
from some small number of use cases.
This patch allows using indexes other than PRIMARY KEY or REPLICA
IDENTITY on the subscriber during apply of update/delete. The index that
can be used must be a btree index, not a partial index, and it must have
at least one column reference (i.e. cannot consist of only expressions).
We can uplift these restrictions in the future. There is no smart
mechanism to pick the index. If there is more than one index that
satisfies these requirements, we just pick the first one. We discussed
using some of the optimizer's low-level APIs for this but ruled it out
as that can be a maintenance burden in the long run.
This patch improves the performance in the vast majority of cases and the
improvement is proportional to the amount of data in the table. However,
there could be some regression in a small number of cases where the indexes
have a lot of duplicate and dead rows. It was discussed that those are
mostly impractical cases but we can provide a table or subscription level
option to disable this feature if required.
Author: Onder Kalaci, Amit Kapila
Reviewed-by: Peter Smith, Shi yu, Hou Zhijie, Vignesh C, Kuroda Hayato, Amit Kapila
Discussion: https://postgr.es/m/CACawEhVLqmAAyPXdHEPv1ssU2c=dqOniiGz7G73HfyS7+nGV4w@mail.gmail.com
Add leader_pid to pg_stat_subscription. leader_pid is the process ID of
the leader apply worker if this process is a parallel apply worker. If
this field is NULL, it indicates that the process is a leader apply
worker or a synchronization worker. The new column makes it easier to
distinguish parallel apply workers from other kinds of workers and helps
to identify the leader for the parallel workers corresponding to a
particular subscription.
Additionally, update the leader_pid column in pg_stat_activity as well to
display the PID of the leader apply worker for parallel apply workers.
Author: Hou Zhijie
Reviewed-by: Peter Smith, Sawada Masahiko, Amit Kapila, Shveta Mallik
Discussion: https://postgr.es/m/CAA4eK1+wyN6zpaHUkCLorEWNx75MG0xhMwcFhvjqm2KURZEAGw@mail.gmail.com
Currently, for large transactions, the publisher sends the data in
multiple streams (changes divided into chunks depending upon
logical_decoding_work_mem), and then on the subscriber-side, the apply
worker writes the changes into temporary files and once it receives the
commit, it reads from those files and applies the entire transaction. To
improve the performance of such transactions, we can instead allow them to
be applied via parallel workers.
In this approach, we assign a new parallel apply worker (if available) as
soon as the xact's first stream is received and the leader apply worker
will send changes to this new worker via shared memory. The parallel apply
worker will directly apply the change instead of writing it to temporary
files. However, if the leader apply worker times out while attempting to
send a message to the parallel apply worker, it will switch to
"partial serialize" mode - in this mode, the leader serializes all
remaining changes to a file and notifies the parallel apply workers to
read and apply them at the end of the transaction. We use a non-blocking
way to send the messages from the leader apply worker to the parallel
apply to avoid deadlocks. We keep this parallel apply assigned till the
transaction commit is received and also wait for the worker to finish at
commit. This preserves commit ordering and avoid writing to and reading
from files in most cases. We still need to spill if there is no worker
available.
This patch also extends the SUBSCRIPTION 'streaming' parameter so that the
user can control whether to apply the streaming transaction in a parallel
apply worker or spill the change to disk. The user can set the streaming
parameter to 'on/off', or 'parallel'. The parameter value 'parallel' means
the streaming will be applied via a parallel apply worker, if available.
The parameter value 'on' means the streaming transaction will be spilled
to disk. The default value is 'off' (same as current behaviour).
In addition, the patch extends the logical replication STREAM_ABORT
message so that abort_lsn and abort_time can also be sent which can be
used to update the replication origin in parallel apply worker when the
streaming transaction is aborted. Because this message extension is needed
to support parallel streaming, parallel streaming is not supported for
publications on servers < PG16.
Author: Hou Zhijie, Wang wei, Amit Kapila with design inputs from Sawada Masahiko
Reviewed-by: Sawada Masahiko, Peter Smith, Dilip Kumar, Shi yu, Kuroda Hayato, Shveta Mallik
Discussion: https://postgr.es/m/CAA4eK1+wyN6zpaHUkCLorEWNx75MG0xhMwcFhvjqm2KURZEAGw@mail.gmail.com
After some copy-edit I made in commit 3a06a79cd1, we have a <sect2>
that only contains a warning box. This doesn't look good. Rework by
moving the sect2 title to be the warning's title, and put the 'id' to it
as well, so that the external reference continues to work.
Backpatch to 15.
In branch master, I also take the opportunity to add titles to a couple
of other warning boxes elsewhere in the documentation.
Discussion: https://postgr.es/m/20221219164713.ccnlvtkyj6lmshqq@alvherre.pgsql
There are some cases (e.g. when the subscription is created using the
connect = false option) where the remote replication slot was not created
automatically and the user must create it manually before the subscription
can be activated. There was not enough information in the docs for users
to do this easily.
Author: Peter Smith
Reviewd by: Shi yu, Amit Kapila
Discussion: https://postgr.es/m/CAHut+PvqdqOanheWSHDyhQiF+Z-7w=-+k4U+bwbT=b6YQ_hrXQ@mail.gmail.com
