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Skip checkpoints, archiving on idle systems.

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Some background activity (like checkpoints, archive timeout, standby
snapshots) is not supposed to happen on an idle system. Unfortunately
so far it was not easy to determine when a system is idle, which
defeated some of the attempts to avoid redundant activity on an idle
system.

To make that easier, allow to make individual WAL insertions as not
being "important". By checking whether any important activity happened
since the last time an activity was performed, it now is easy to check
whether some action needs to be repeated.

Use the new facility for checkpoints, archive timeout and standby
snapshots.

The lack of a facility causes some issues in older releases, but in my
opinion the consequences (superflous checkpoints / archived segments)
aren't grave enough to warrant backpatching.

Author: Michael Paquier, editorialized by Andres Freund
Reviewed-By: Andres Freund, David Steele, Amit Kapila, Kyotaro HORIGUCHI
Bug: #13685
Discussion:
    https://www.postgresql.org/message-id/20151016203031.3019.72930@wrigleys.postgresql.org
    https://www.postgresql.org/message-id/CAB7nPqQcPqxEM3S735Bd2RzApNqSNJVietAC=6kfkYv_45dKwA@mail.gmail.com
Backpatch: -
This commit is contained in:
Andres Freund
2016-12-22 11:31:50 -08:00
parent 097e41439d
commit 6ef2eba3f5
13 changed files with 173 additions and 77 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
src/include/access/xlog.h
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@@ -184,6 +184,13 @@ extern bool XLOG_DEBUG;
#define CHECKPOINT_CAUSE_XLOG 0x0040 /* XLOG consumption */
#define CHECKPOINT_CAUSE_TIME 0x0080 /* Elapsed time */
/*
* Flag bits for the record being inserted, set using XLogSetRecordFlags().
*/
#define XLOG_INCLUDE_ORIGIN 0x01 /* include the replication origin */
#define XLOG_MARK_UNIMPORTANT 0x02 /* record not important for durability */
/* Checkpoint statistics */
typedef struct CheckpointStatsData
{
@@ -211,7 +218,9 @@ extern CheckpointStatsData CheckpointStats;
struct XLogRecData;
extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata, XLogRecPtr fpw_lsn);
extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
XLogRecPtr fpw_lsn,
uint8 flags);
extern void XLogFlush(XLogRecPtr RecPtr);
extern bool XLogBackgroundFlush(void);
extern bool XLogNeedsFlush(XLogRecPtr RecPtr);
@@ -262,6 +271,7 @@ extern void GetFullPageWriteInfo(XLogRecPtr *RedoRecPtr_p, bool *doPageWrites_p)
extern XLogRecPtr GetRedoRecPtr(void);
extern XLogRecPtr GetInsertRecPtr(void);
extern XLogRecPtr GetFlushRecPtr(void);
extern XLogRecPtr GetLastImportantRecPtr(void);
extern void GetNextXidAndEpoch(TransactionId *xid, uint32 *epoch);
extern void RemovePromoteSignalFiles(void);