diff options
| author | Amit Kapila | 2025-02-25 04:12:07 +0000 |
|---|---|---|
| committer | Amit Kapila | 2025-02-25 04:12:07 +0000 |
| commit | 5b8f2ccc0a93375acb64a457817e61f400404a1f (patch) | |
| tree | ed3312e21230ca9524c6d63535e1f5b902e75464 | |
| parent | 15601fa21a5509b83a871c39ab98671f560da905 (diff) | |
Doc: Fix pg_copy_logical_replication_slot description.
This commit documents that the failover option is not copied when using
the pg_copy_logical_replication_slot function.
In passing, we modify the comments in the function clarifying the reason
for this behavior.
Reported-by: <[email protected]>
Author: Hou Zhijie <[email protected]>
Reviewed-by: Amit Kapila <[email protected]>
Backpatch-through: 17, where it was introduced
Discussion: https://postgr.es/m/[email protected]
| -rw-r--r-- | doc/src/sgml/func.sgml | 4 | ||||
| -rw-r--r-- | src/backend/replication/slotfuncs.c | 19 |
2 files changed, 16 insertions, 7 deletions
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml index 21a8ea42f5f..f0ccb751106 100644 --- a/doc/src/sgml/func.sgml +++ b/doc/src/sgml/func.sgml @@ -29374,6 +29374,10 @@ postgres=# SELECT '0/0'::pg_lsn + pd.segment_number * ps.setting::int + :offset from the same <acronym>LSN</acronym> as the source logical slot. Both <parameter>temporary</parameter> and <parameter>plugin</parameter> are optional; if they are omitted, the values of the source slot are used. + The <literal>failover</literal> option of the source logical slot + is not copied and is set to <literal>false</literal> by default. This + is to avoid the risk of being unable to continue logical replication + after failover to standby where the slot is being synchronized. </para></entry> </row> diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c index f652ec8a73e..146eef5871e 100644 --- a/src/backend/replication/slotfuncs.c +++ b/src/backend/replication/slotfuncs.c @@ -695,13 +695,18 @@ copy_replication_slot(FunctionCallInfo fcinfo, bool logical_slot) * hence pass find_startpoint false. confirmed_flush will be set * below, by copying from the source slot. * - * To avoid potential issues with the slot synchronization where the - * restart_lsn of a replication slot can go backward, we set the - * failover option to false here. This situation occurs when a slot - * on the primary server is dropped and immediately replaced with a - * new slot of the same name, created by copying from another existing - * slot. However, the slot synchronization will only observe the - * restart_lsn of the same slot going backward. + * We don't copy the failover option to prevent potential issues with + * slot synchronization. For instance, if a slot was synchronized to + * the standby, then dropped on the primary, and immediately recreated + * by copying from another existing slot with much earlier restart_lsn + * and confirmed_flush_lsn, the slot synchronization would only + * observe the LSN of the same slot moving backward. As slot + * synchronization does not copy the restart_lsn and + * confirmed_flush_lsn backward (see update_local_synced_slot() for + * details), if a failover happens before the primary's slot catches + * up, logical replication cannot continue using the synchronized slot + * on the promoted standby because the slot retains the restart_lsn + * and confirmed_flush_lsn that are much later than expected. */ create_logical_replication_slot(NameStr(*dst_name), plugin, |