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Commit81fe138

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Fix memory leak in LogStandbySnapshot().
The array allocated by GetRunningTransactionLocks() needs to be pfree'dwhen we're done with it. Otherwise we leak some memory during eachcheckpoint, if wal_level = hot_standby. This manifests as memory bloatin the checkpointer process, or in bgwriter in versions before we madethe checkpointer separate.Reported and fixed by Naoya Anzai. Back-patch to 9.0 where the issuewas introduced.In passing, improve comments for GetRunningTransactionLocks(), and addan Assert that we didn't overrun the palloc'd array.
1 parentcc510d9 commit81fe138

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2 files changed

+14
-9
lines changed

2 files changed

+14
-9
lines changed

‎src/backend/storage/ipc/standby.c‎

Lines changed: 1 addition & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -875,16 +875,11 @@ LogStandbySnapshot(void)
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/*
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* Get details of any AccessExclusiveLocks being held at the moment.
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*
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* XXX GetRunningTransactionLocks() currently holds a lock on all
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* partitions though it is possible to further optimise the locking. By
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* reference counting locks and storing the value on the ProcArray entry
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* for each backend we can easily tell if any locks need recording without
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* trying to acquire the partition locks and scanning the lock table.
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*/
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locks=GetRunningTransactionLocks(&nlocks);
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if (nlocks>0)
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LogAccessExclusiveLocks(nlocks,locks);
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pfree(locks);
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/*
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* Log details of all in-progress transactions. This should be the last

‎src/backend/storage/lmgr/lock.c‎

Lines changed: 13 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -3353,18 +3353,26 @@ GetLockStatusData(void)
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}
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/*
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* Returns a list of currently held AccessExclusiveLocks, for use
3357-
* by GetRunningTransactionData().
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* Returns a list of currently held AccessExclusiveLocks, for use by
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* LogStandbySnapshot(). The result is a palloc'd array,
3358+
* with the number of elements returned into *nlocks.
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*
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* XXX This currently takes a lock on all partitions of the lock table,
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* but it's possible to do better. By reference counting locks and storing
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* the value in the ProcArray entry for each backend we could tell if any
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* locks need recording without having to acquire the partition locks and
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* scan the lock table. Whether that's worth the additional overhead
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* is pretty dubious though.
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*/
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xl_standby_lock*
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GetRunningTransactionLocks(int*nlocks)
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{
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xl_standby_lock*accessExclusiveLocks;
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PROCLOCK*proclock;
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HASH_SEQ_STATUSseqstat;
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inti;
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intindex;
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intels;
3367-
xl_standby_lock*accessExclusiveLocks;
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/*
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* Acquire lock on the entire shared lock data structure.
@@ -3422,6 +3430,8 @@ GetRunningTransactionLocks(int *nlocks)
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}
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}
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3433+
Assert(index <=els);
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/*
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* And release locks. We do this in reverse order for two reasons: (1)
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* Anyone else who needs more than one of the locks will be trying to lock

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