Logical replication requires reliable conflict detection to maintain data
consistency across nodes. To achieve this, we must prevent premature
removal of tuples deleted by other origins and their associated commit_ts
data by VACUUM, which could otherwise lead to incorrect conflict reporting
and resolution.
This patch introduces a mechanism to retain deleted tuples on the
subscriber during the application of concurrent transactions from remote
nodes. Retaining these tuples allows us to correctly ignore concurrent
updates to the same tuple. Without this, an UPDATE might be misinterpreted
as an INSERT during resolutions due to the absence of the original tuple.
Additionally, we ensure that origin metadata is not prematurely removed by
vacuum freeze, which is essential for detecting update_origin_differs and
delete_origin_differs conflicts.
To support this, a new replication slot named pg_conflict_detection is
created and maintained by the launcher on the subscriber. Each apply
worker tracks its own non-removable transaction ID, which the launcher
aggregates to determine the appropriate xmin for the slot, thereby
retaining necessary tuples.
Conflict information retention (deleted tuples and commit_ts) can be
enabled per subscription via the retain_conflict_info option. This is
disabled by default to avoid unnecessary overhead for configurations that
do not require conflict resolution or logging.
During upgrades, if any subscription on the old cluster has
retain_conflict_info enabled, a conflict detection slot will be created to
protect relevant tuples from deletion when the new cluster starts.
This is a foundational work to correctly detect update_deleted conflict
which will be done in a follow-up patch.
Author: Zhijie Hou <houzj.fnst@fujitsu.com>
Reviewed-by: shveta malik <shveta.malik@gmail.com>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Reviewed-by: Dilip Kumar <dilipbalaut@gmail.com>
Reviewed-by: Nisha Moond <nisha.moond412@gmail.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Discussion: https://postgr.es/m/OS0PR01MB5716BE80DAEB0EE2A6A5D1F5949D2@OS0PR01MB5716.jpnprd01.prod.outlook.com
/* Prepare the list of publication(s) for warning message. */
GetPublicationsStr(publist,pubnames,false);
if(check_table_sync)
{
appendStringInfo(err_msg,_("subscription \"%s\" requested copy_data with origin = NONE but might copy data that had a different origin"),
subname);
appendStringInfoString(err_hint,_("Verify that initial data copied from the publisher tables did not come from other origins."));
}
else
{
appendStringInfo(err_msg,_("subscription \"%s\" enabled retain_dead_tuples but might not reliably detect conflicts for changes from different origins"),
subname);
appendStringInfoString(err_hint,_("Consider using origin = NONE or disabling retain_dead_tuples."));
# pg_upgrade will fail because the new cluster has insufficient
# max_replication_slots.
command_checks_all(
[
'pg_upgrade',
'--no-sync',
'--old-datadir'=>$old_sub->data_dir,
'--new-datadir'=>$new_sub->data_dir,
'--old-bindir'=>$oldbindir,
'--new-bindir'=>$newbindir,
'--socketdir'=>$new_sub->host,
'--old-port'=>$old_sub->port,
'--new-port'=>$new_sub->port,
$mode,
'--check',
],
1,
[
qr/"max_replication_slots" \(0\) must be greater than or equal to the number of logical replication slots on the old cluster plus one additional slot required for retaining conflict detection information \(1\)/
],
[qr//],
'run of pg_upgrade where the new cluster has insufficient max_replication_slots'
regress_testsub4 | regress_subscription_user | f | {testpub} | f | parallel | d | f | none | t | f | f | off | dbname=regress_doesnotexist | 0/00000000
List of subscriptions
Name | Owner | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Retain dead tuples | Synchronous commit | Conninfo | Skip LSN
regress_testsub4 | regress_subscription_user | f | {testpub} | f | parallel | d | f | none | t | f | f | f | off | dbname=regress_doesnotexist | 0/00000000
(1 row)
ALTER SUBSCRIPTION regress_testsub4 SET (origin = any);
\dRs+ regress_testsub4
List of subscriptions
Name | Owner | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit | Conninfo | Skip LSN
regress_testsub4 | regress_subscription_user | f | {testpub} | f | parallel | d | f | any | t | f | f | f | off | dbname=regress_doesnotexist | 0/00000000
(1 row)
DROP SUBSCRIPTION regress_testsub3;
@ -145,10 +145,10 @@ ALTER SUBSCRIPTION regress_testsub CONNECTION 'foobar';
ERROR: invalid connection string syntax: missing "=" after "foobar" in connection info string
\dRs+
List of subscriptions
Name | Owner | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit | Conninfo | Skip LSN
regress_testsub | regress_subscription_user | f | {testpub} | f | parallel | d | f | any | t | f | f | f | off | dbname=regress_doesnotexist | 0/00000000
(1 row)
ALTER SUBSCRIPTION regress_testsub SET PUBLICATION testpub2, testpub3 WITH (refresh = false);
@ -157,10 +157,10 @@ ALTER SUBSCRIPTION regress_testsub SET (slot_name = 'newname');
ALTER SUBSCRIPTION regress_testsub SET (password_required = false);
ALTER SUBSCRIPTION regress_testsub SET (run_as_owner = true);
\dRs+
List of subscriptions
Name | Owner | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit | Conninfo | Skip LSN
regress_testsub | regress_subscription_user | f | {testpub2,testpub3} | f | parallel | d | f | any | f | t | f | off | dbname=regress_doesnotexist2 | 0/00000000
List of subscriptions
Name | Owner | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Retain dead tuples | Synchronous commit | Conninfo | Skip LSN
regress_testsub | regress_subscription_user | f | {testpub2,testpub3} | f | parallel | d | f | any | f | t | f | f | off | dbname=regress_doesnotexist2 | 0/00000000
(1 row)
ALTER SUBSCRIPTION regress_testsub SET (password_required = true);
regress_testsub | regress_subscription_user | f | {testpub2,testpub3} | f | parallel | d | f | any | t | f | f | off | dbname=regress_doesnotexist2 | 0/00012345
List of subscriptions
Name | Owner | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Retain dead tuples | Synchronous commit | Conninfo | Skip LSN
regress_testsub | regress_subscription_user | f | {testpub2,testpub3} | f | parallel | d | f | any | t | f | f | f | off | dbname=regress_doesnotexist2 | 0/00012345
regress_testsub | regress_subscription_user | f | {testpub2,testpub3} | f | parallel | d | f | any | t | f | f | off | dbname=regress_doesnotexist2 | 0/00000000
List of subscriptions
Name | Owner | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Retain dead tuples | Synchronous commit | Conninfo | Skip LSN
regress_testsub | regress_subscription_user | f | {testpub2,testpub3} | f | parallel | d | f | any | t | f | f | f | off | dbname=regress_doesnotexist2 | 0/00000000
(1 row)
BEGIN;
@ -223,10 +223,10 @@ ALTER SUBSCRIPTION regress_testsub_foo SET (synchronous_commit = foobar);
ERROR: invalid value for parameter "synchronous_commit": "foobar"
HINT: Available values: local, remote_write, remote_apply, on, off.
\dRs+
List of subscriptions
Name | Owner | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit | Conninfo | Skip LSN
regress_testsub_foo | regress_subscription_user | f | {testpub2,testpub3} | f | parallel | d | f | any | t | f | f | local | dbname=regress_doesnotexist2 | 0/00000000
List of subscriptions
Name | Owner | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Retain dead tuples | Synchronous commit | Conninfo | Skip LSN
regress_testsub_foo | regress_subscription_user | f | {testpub2,testpub3} | f | parallel | d | f | any | t | f | f | f | local | dbname=regress_doesnotexist2 | 0/00000000
regress_testsub | regress_subscription_user | f | {testpub} | t | parallel | d | f | any | t | f | f | f | off | dbname=regress_doesnotexist | 0/00000000
(1 row)
ALTER SUBSCRIPTION regress_testsub SET (binary = false);
ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
\dRs+
List of subscriptions
Name | Owner | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit | Conninfo | Skip LSN
regress_testsub | regress_subscription_user | f | {testpub} | f | parallel | d | f | any | t | f | f | f | off | dbname=regress_doesnotexist | 0/00000000
regress_testsub | regress_subscription_user | f | {testpub} | f | parallel | d | f | any | t | f | f | f | off | dbname=regress_doesnotexist | 0/00000000
(1 row)
ALTER SUBSCRIPTION regress_testsub SET (streaming = false);
ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
\dRs+
List of subscriptions
Name | Owner | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit | Conninfo | Skip LSN
regress_testsub | regress_subscription_user | f | {testpub,testpub1,testpub2} | f | off | d | f | any | t | f | f | off | dbname=regress_doesnotexist | 0/00000000
List of subscriptions
Name | Owner | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Retain dead tuples | Synchronous commit | Conninfo | Skip LSN
regress_testsub | regress_subscription_user | f | {testpub,testpub1,testpub2} | f | off | d | f | any | t | f | f | f | off | dbname=regress_doesnotexist | 0/00000000
(1 row)
-- fail - publication used more than once
@ -332,10 +332,10 @@ ERROR: publication "testpub3" is not in subscription "regress_testsub"
-- ok - delete publications
ALTER SUBSCRIPTION regress_testsub DROP PUBLICATION testpub1, testpub2 WITH (refresh = false);
\dRs+
List of subscriptions
Name | Owner | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit | Conninfo | Skip LSN
regress_testsub | regress_subscription_user | f | {testpub} | f | parallel | p | f | any | t | f | f | f | off | dbname=regress_doesnotexist | 0/00000000
(1 row)
-- we can alter streaming when two_phase enabled
ALTER SUBSCRIPTION regress_testsub SET (streaming = true);
\dRs+
List of subscriptions
Name | Owner | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit | Conninfo | Skip LSN
regress_testsub | regress_subscription_user | f | {testpub} | f | parallel | d | f | any | t | f | f | f | off | dbname=regress_doesnotexist | 0/00000000
(1 row)
ALTER SUBSCRIPTION regress_testsub SET (disable_on_error = true);
\dRs+
List of subscriptions
Name | Owner | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Password required | Run as owner? | Failover | Synchronous commit | Conninfo | Skip LSN
regress_testsub | regress_subscription_user | f | {testpub} | f | parallel | d | t | any | t | f | f | f | off | dbname=regress_doesnotexist | 0/00000000
(1 row)
ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
regress_testsub | regress_subscription_user | f | {testpub} | f | parallel | d | f | any | t | f | f | f | off | dbname=regress_doesnotexist | 0/00000000
(1 row)
ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
Amit Kapila
2 months ago