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Update more comments about checkpoints being done by bgwriter

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This commit is contained in:
Simon Riggs 2011-11-02 17:15:35 +00:00
parent 18fb9d8d21
commit 750f70b0fe
1 changed files with 10 additions and 10 deletions
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20
src/backend/access/transam/xlog.c
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@ -326,7 +326,7 @@ static XLogRecPtr RedoStartLSN = {0, 0};
* *
* CheckpointLock: must be held to do a checkpoint or restartpoint (ensures * CheckpointLock: must be held to do a checkpoint or restartpoint (ensures
* only one checkpointer at a time; currently, with all checkpoints done by * only one checkpointer at a time; currently, with all checkpoints done by
* the bgwriter, this is just pro forma). * the checkpointer, this is just pro forma).
* *
*---------- *----------
*/ */
@ -411,7 +411,7 @@ typedef struct XLogCtlData
/* /*
* archiveCleanupCommand is read from recovery.conf but needs to be in * archiveCleanupCommand is read from recovery.conf but needs to be in
* shared memory so that the bgwriter process can access it. * shared memory so that the checkpointer process can access it.
*/ */
char archiveCleanupCommand[MAXPGPATH]; char archiveCleanupCommand[MAXPGPATH];
@ -1837,7 +1837,7 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible, bool xlog_switch)
Write->lastSegSwitchTime = (pg_time_t) time(NULL); Write->lastSegSwitchTime = (pg_time_t) time(NULL);
/* /*
* Signal bgwriter to start a checkpoint if we've consumed too * Request a checkpoint if we've consumed too
* much xlog since the last one. For speed, we first check * much xlog since the last one. For speed, we first check
* using the local copy of RedoRecPtr, which might be out of * using the local copy of RedoRecPtr, which might be out of
* date; if it looks like a checkpoint is needed, forcibly * date; if it looks like a checkpoint is needed, forcibly
@ -2023,8 +2023,8 @@ XLogFlush(XLogRecPtr record)
/* /*
* During REDO, we are reading not writing WAL. Therefore, instead of * During REDO, we are reading not writing WAL. Therefore, instead of
* trying to flush the WAL, we should update minRecoveryPoint instead. We * trying to flush the WAL, we should update minRecoveryPoint instead. We
* test XLogInsertAllowed(), not InRecovery, because we need the bgwriter * test XLogInsertAllowed(), not InRecovery, because we need checkpointer
* to act this way too, and because when the bgwriter tries to write the * to act this way too, and because when it tries to write the
* end-of-recovery checkpoint, it should indeed flush. * end-of-recovery checkpoint, it should indeed flush.
*/ */
if (!XLogInsertAllowed()) if (!XLogInsertAllowed())
@ -5856,7 +5856,7 @@ pg_is_xlog_replay_paused(PG_FUNCTION_ARGS)
* *
* We keep this in XLogCtl, not a simple static variable, so that it can be * We keep this in XLogCtl, not a simple static variable, so that it can be
* seen by processes other than the startup process. Note in particular * seen by processes other than the startup process. Note in particular
* that CreateRestartPoint is executed in the bgwriter. * that CreateRestartPoint is executed in the checkpointer.
*/ */
static void static void
SetLatestXTime(TimestampTz xtime) SetLatestXTime(TimestampTz xtime)
@ -6464,14 +6464,14 @@ StartupXLOG(void)
/* /*
* Let postmaster know we've started redo now, so that it can launch * Let postmaster know we've started redo now, so that it can launch
* bgwriter to perform restartpoints. We don't bother during crash * checkpointer to perform restartpoints. We don't bother during crash
* recovery as restartpoints can only be performed during archive * recovery as restartpoints can only be performed during archive
* recovery. And we'd like to keep crash recovery simple, to avoid * recovery. And we'd like to keep crash recovery simple, to avoid
* introducing bugs that could affect you when recovering after crash. * introducing bugs that could affect you when recovering after crash.
* *
* After this point, we can no longer assume that we're the only * After this point, we can no longer assume that we're the only
* process in addition to postmaster! Also, fsync requests are * process in addition to postmaster! Also, fsync requests are
* subsequently to be handled by the bgwriter, not locally. * subsequently to be handled by the checkpointer, not locally.
*/ */
if (InArchiveRecovery && IsUnderPostmaster) if (InArchiveRecovery && IsUnderPostmaster)
{ {
@ -7969,8 +7969,8 @@ CheckPointGuts(XLogRecPtr checkPointRedo, int flags)
* It must determine whether the checkpoint represents a safe restartpoint or * It must determine whether the checkpoint represents a safe restartpoint or
* not. If so, the checkpoint record is stashed in shared memory so that * not. If so, the checkpoint record is stashed in shared memory so that
* CreateRestartPoint can consult it. (Note that the latter function is * CreateRestartPoint can consult it. (Note that the latter function is
* executed by the bgwriter, while this one will be executed by the startup * executed by the checkpointer, while this one will be executed by the
* process.) * startup process.)
*/ */
static void static void
RecoveryRestartPoint(const CheckPoint *checkPoint) RecoveryRestartPoint(const CheckPoint *checkPoint)