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Arrange for large sequential scans to synchronize with each other, so that

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when multiple backends are scanning the same relation concurrently, each page
is (ideally) read only once.

Jeff Davis, with review by Heikki and Tom.
This commit is contained in:
Tom Lane
2007-06-08 18:23:53 +00:00
parent 6d6d14b6d5
commit a04a423599
10 changed files with 485 additions and 31 deletions
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24
src/include/access/heapam.h
View File

@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/access/heapam.h,v 1.124 2007/05/27 03:50:39 tgl Exp $
* $PostgreSQL: pgsql/src/include/access/heapam.h,v 1.125 2007/06/08 18:23:53 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -112,6 +112,13 @@ extern Datum fastgetattr(HeapTuple tup, int attnum, TupleDesc tupleDesc,
)
typedef enum
{
LockTupleShared,
LockTupleExclusive
} LockTupleMode;
/* ----------------
* function prototypes for heap access method
*
@@ -120,14 +127,7 @@ extern Datum fastgetattr(HeapTuple tup, int attnum, TupleDesc tupleDesc,
* ----------------
*/
/* heapam.c */
typedef enum
{
LockTupleShared,
LockTupleExclusive
} LockTupleMode;
/* in heap/heapam.c */
extern Relation relation_open(Oid relationId, LOCKMODE lockmode);
extern Relation try_relation_open(Oid relationId, LOCKMODE lockmode);
extern Relation relation_open_nowait(Oid relationId, LOCKMODE lockmode);
@@ -240,4 +240,10 @@ extern HeapTuple heap_addheader(int natts, bool withoid,
extern void heap_sync(Relation relation);
/* in heap/syncscan.c */
extern void ss_report_location(Relation rel, BlockNumber location);
extern BlockNumber ss_get_location(Relation rel, BlockNumber relnblocks);
extern void SyncScanShmemInit(void);
extern Size SyncScanShmemSize(void);
#endif /* HEAPAM_H */

6
src/include/access/relscan.h
View File

@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/access/relscan.h,v 1.54 2007/05/30 20:12:02 tgl Exp $
* $PostgreSQL: pgsql/src/include/access/relscan.h,v 1.55 2007/06/08 18:23:53 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -26,9 +26,13 @@ typedef struct HeapScanDescData
Snapshot rs_snapshot; /* snapshot to see */
int rs_nkeys; /* number of scan keys */
ScanKey rs_key; /* array of scan key descriptors */
/* state set up at initscan time */
BlockNumber rs_nblocks; /* number of blocks to scan */
BlockNumber rs_startblock; /* block # to start at */
BufferAccessStrategy rs_strategy; /* access strategy for reads */
bool rs_pageatatime; /* verify visibility page-at-a-time? */
bool rs_syncscan; /* report location to syncscan logic? */
/* scan current state */
bool rs_inited; /* false = scan not init'd yet */