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Update more obsolete multixact.c comments. 

Update some remaining comments in multixact.c that still described SLRU
truncation as happening in the checkpointer, rather than during VACUUM.

Follow-up to commit 5212d447.

Shi yu, with tweaks by me.

Author: Shi yu <shiy.fnst@fujitsu.com>
Discussion: https://postgr.es/m/OSZPR01MB631066BF246F8F74E83222FCFDC69@OSZPR01MB6310.jpnprd01.prod.outlook.com
This commit is contained in:
Peter Geoghegan 2023-01-24 15:15:33 -08:00
parent 1249371632
commit 8f8f115932
1 changed files with 3 additions and 3 deletions
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6
src/backend/access/transam/multixact.c
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@ -261,7 +261,7 @@ typedef struct MultiXactStateData
* we compute it (using nextMXact if none are valid). Each backend is
* required not to attempt to access any SLRU data for MultiXactIds older
* than its own OldestVisibleMXactId[] setting; this is necessary because
* the checkpointer could truncate away such data at any instant.
* the relevant SLRU data can be concurrently truncated away.
*
* The oldest valid value among all of the OldestMemberMXactId[] and
* OldestVisibleMXactId[] entries is considered by vacuum as the earliest
@ -669,8 +669,8 @@ MultiXactIdSetOldestMember(void)
*
* We set the OldestVisibleMXactId for a given transaction the first time
* it's going to inspect any MultiXactId. Once we have set this, we are
* guaranteed that the checkpointer won't truncate off SLRU data for
* MultiXactIds at or after our OldestVisibleMXactId.
* guaranteed that SLRU data for MultiXactIds >= our own OldestVisibleMXactId
* won't be truncated away.
*
* The value to set is the oldest of nextMXact and all the valid per-backend
* OldestMemberMXactId[] entries. Because of the locking we do, we can be