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Commite1e2bb3

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committed
Code review of recycling WAL segments in a restartpoint.
Seems cleaner to get the currently-replayed TLI in the same call toGetXLogReplayRecPtr that we get the WAL position. Make it more clear in thecomment what the code does when recovery has already ended(RecoveryInProgress() will set ThisTimeLineID in that case). Finally, makeresetting ThisTimeLineID afterwards more explicit.
1 parent2c92eda commite1e2bb3

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1 file changed

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lines changed
  • src/backend/access/transam

1 file changed

+15
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‎src/backend/access/transam/xlog.c

Lines changed: 15 additions & 15 deletions
Original file line numberDiff line numberDiff line change
@@ -7463,39 +7463,35 @@ CreateRestartPoint(int flags)
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{
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XLogRecPtrreceivePtr;
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XLogRecPtrreplayPtr;
7466+
TimeLineIDreplayTLI;
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XLogRecPtrendptr;
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/*
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* Get the current end of xlog replayed or received, whichever is
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* later.
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*/
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receivePtr=GetWalRcvWriteRecPtr(NULL,NULL);
7473-
replayPtr=GetXLogReplayRecPtr(NULL);
7474+
replayPtr=GetXLogReplayRecPtr(&replayTLI);
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endptr= (receivePtr<replayPtr) ?replayPtr :receivePtr;
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74767477
KeepLogSeg(endptr,&_logSegNo);
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_logSegNo--;
74787479

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/*
7480-
* Update ThisTimeLineID to the timeline we're currently replaying, so
7481-
* that we install any recycled segments on that timeline.
7481+
* Try to recycle segments on a useful timeline. If we've been promoted
7482+
* since the beginning of this restartpoint, use the new timeline
7483+
* chosen at end of recovery (RecoveryInProgress() sets ThisTimeLineID
7484+
* in that case). If we're still in recovery, use the timeline we're
7485+
* currently replaying.
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*
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* There is no guarantee that the WAL segments will be useful on the
74847488
* current timeline; if recovery proceeds to a new timeline right
74857489
* after this, the pre-allocated WAL segments on this timeline will
74867490
* not be used, and will go wasted until recycled on the next
74877491
* restartpoint. We'll live with that.
7488-
*
7489-
* It's possible or perhaps even likely that we finish recovery while
7490-
* a restartpoint is in progress. That means we may get to this point
7491-
* some minutes afterwards. Setting ThisTimeLineID at that time would
7492-
* actually set it backwards, so we don't want that to persist; if we
7493-
* do reset it here, make sure to reset it back afterwards. This
7494-
* doesn't look very clean or principled, but its the best of about
7495-
* five different ways of handling this edge case.
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*/
74977493
if (RecoveryInProgress())
7498-
(void)GetXLogReplayRecPtr(&ThisTimeLineID);
7494+
ThisTimeLineID=replayTLI;
74997495

75007496
RemoveOldXlogFiles(_logSegNo,endptr);
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@@ -7506,10 +7502,14 @@ CreateRestartPoint(int flags)
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PreallocXlogFiles(endptr);
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75087504
/*
7509-
* Reset this always, in case we set ThisTimeLineID backwards above.
7510-
* Requires no locking; see InitXLOGAccess()
7505+
* ThisTimeLineID is normally not set when we're still in recovery.
7506+
* However, recycling/preallocating segments above needed
7507+
* ThisTimeLineID to determine which timeline to install the segments
7508+
* on. Reset it now, to restore the normal state of affairs for
7509+
* debugging purposes.
75117510
*/
7512-
ThisTimeLineID=XLogCtl->ThisTimeLineID;
7511+
if (RecoveryInProgress())
7512+
ThisTimeLineID=0;
75137513
}
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75157515
/*

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