database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-27 12:41:57 +03:00
Code Activity

Improve handling of prune/no-prune decisions by storing a page's oldest

Browse Source 
unpruned XMAX in its header.  At the cost of 4 bytes per page, this keeps us
from performing heap_page_prune when there's no chance of pruning anything.
Seems to be necessary per Heikki's preliminary performance testing.
This commit is contained in:
Tom Lane
2007-09-21 21:25:42 +00:00
parent 386a5d4268
commit cc59049daf
10 changed files with 92 additions and 59 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
src/backend/access/heap/README.HOT
View File

@ -1,4 +1,4 @@
$PostgreSQL: pgsql/src/backend/access/heap/README.HOT,v 1.1 2007/09/20 17:56:30 tgl Exp $
$PostgreSQL: pgsql/src/backend/access/heap/README.HOT,v 1.2 2007/09/21 21:25:42 tgl Exp $
Heap Only Tuples (HOT)
@ -233,8 +233,8 @@ subsequent index searches. However it is unclear that this gain is
large enough to accept any extra maintenance burden for.
The currently planned heuristic is to prune and defrag when first accessing
a page that potentially has prunable tuples (flagged by the PD_PRUNABLE
page hint bit) and that either has free space less than MAX(fillfactor
a page that potentially has prunable tuples (as flagged by the pd_prune_xid
page hint field) and that either has free space less than MAX(fillfactor
target free space, BLCKSZ/10) *or* has recently had an UPDATE fail to
find enough free space to store an updated tuple version. (These rules
are subject to change.)

26
src/backend/access/heap/heapam.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.241 2007/09/20 17:56:30 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.242 2007/09/21 21:25:42 tgl Exp $
*
*
* INTERFACE ROUTINES
@ -2068,11 +2068,12 @@ l1:
/*
* If this transaction commits, the tuple will become DEAD sooner or
* later. Set hint bit that this page is a candidate for pruning. If
* the transaction finally aborts, the subsequent page pruning will be
* a no-op and the hint will be cleared.
* later. Set flag that this page is a candidate for pruning once our xid
* falls below the OldestXmin horizon. If the transaction finally aborts,
* the subsequent page pruning will be a no-op and the hint will be
* cleared.
*/
PageSetPrunable((Page) dp);
PageSetPrunable(dp, xid);
/* store transaction information of xact deleting the tuple */
tp.t_data->t_infomask &= ~(HEAP_XMAX_COMMITTED |
@ -2571,16 +2572,17 @@ l2:
/*
* If this transaction commits, the old tuple will become DEAD sooner or
* later. Set hint bit that this page is a candidate for pruning. If
* the transaction finally aborts, the subsequent page pruning will be
* a no-op and the hint will be cleared.
* later. Set flag that this page is a candidate for pruning once our xid
* falls below the OldestXmin horizon. If the transaction finally aborts,
* the subsequent page pruning will be a no-op and the hint will be
* cleared.
*
* XXX Should we set hint on newbuf as well? If the transaction
* aborts, there would be a prunable tuple in the newbuf; but for now
* we choose not to optimize for aborts. Note that heap_xlog_update
* must be kept in sync if this changes.
* must be kept in sync if this decision changes.
*/
PageSetPrunable(dp);
PageSetPrunable(dp, xid);
if (use_hot_update)
{
@ -4108,7 +4110,7 @@ heap_xlog_delete(XLogRecPtr lsn, XLogRecord *record)
HeapTupleHeaderSetCmax(htup, FirstCommandId, false);
/* Mark the page as a candidate for pruning */
PageSetPrunable(page);
PageSetPrunable(page, record->xl_xid);
/* Make sure there is no forward chain link in t_ctid */
htup->t_ctid = xlrec->target.tid;
@ -4284,7 +4286,7 @@ heap_xlog_update(XLogRecPtr lsn, XLogRecord *record, bool move, bool hot_update)
}
/* Mark the page as a candidate for pruning */
PageSetPrunable(page);
PageSetPrunable(page, record->xl_xid);
/*
* this test is ugly, but necessary to avoid thinking that insert change

27
src/backend/access/heap/pruneheap.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/heap/pruneheap.c,v 1.1 2007/09/20 17:56:30 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/heap/pruneheap.c,v 1.2 2007/09/21 21:25:42 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -63,9 +63,10 @@ heap_page_prune_opt(Relation relation, Buffer buffer, TransactionId OldestXmin)
/*
* Let's see if we really need pruning.
*
* Forget it if page is not hinted to contain something prunable
* Forget it if page is not hinted to contain something prunable that's
* older than OldestXmin.
*/
if (!PageIsPrunable(dp))
if (!PageIsPrunable(dp, OldestXmin))
return;
/*
@ -93,6 +94,8 @@ heap_page_prune_opt(Relation relation, Buffer buffer, TransactionId OldestXmin)
/*
* Now that we have buffer lock, get accurate information about the
* page's free space, and recheck the heuristic about whether to prune.
* (We needn't recheck PageIsPrunable, since no one else could have
* pruned while we hold pin.)
*/
if (PageIsFull(dp) || PageGetHeapFreeSpace((Page) dp) < minfree)
{
@ -147,7 +150,7 @@ heap_page_prune(Relation relation, Buffer buffer, TransactionId OldestXmin,
START_CRIT_SECTION();
/*
* Mark the page as clear of prunable tuples. If we find a tuple which
* Mark the page as clear of prunable tuples. If we find a tuple which
* may soon become prunable, we shall set the hint again. Also clear
* the "page is full" flag, since there's no point in repeating the
* prune/defrag process until something else happens to the page.
@ -203,6 +206,14 @@ heap_page_prune(Relation relation, Buffer buffer, TransactionId OldestXmin,
PageSetLSN(BufferGetPage(buffer), recptr);
}
}
else
{
/*
* If we didn't prune anything, we have nonetheless updated the
* pd_prune_xid field; treat this as a non-WAL-logged hint.
*/
SetBufferCommitInfoNeedsSave(buffer);
}
END_CRIT_SECTION();
@ -392,18 +403,18 @@ heap_prune_chain(Relation relation, Buffer buffer, OffsetNumber rootoffnum,
case HEAPTUPLE_RECENTLY_DEAD:
recent_dead = true;
/*
* This tuple may soon become DEAD. Re-set the hint bit so
* This tuple may soon become DEAD. Update the hint field so
* that the page is reconsidered for pruning in future.
*/
PageSetPrunable(dp);
PageSetPrunable(dp, HeapTupleHeaderGetXmax(htup));
break;
case HEAPTUPLE_DELETE_IN_PROGRESS:
/*
* This tuple may soon become DEAD. Re-set the hint bit so
* This tuple may soon become DEAD. Update the hint field so
* that the page is reconsidered for pruning in future.
*/
PageSetPrunable(dp);
PageSetPrunable(dp, HeapTupleHeaderGetXmax(htup));
break;
case HEAPTUPLE_LIVE:

5
src/backend/storage/page/bufpage.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/page/bufpage.c,v 1.74 2007/09/20 17:56:31 tgl Exp $
* $PostgreSQL: pgsql/src/backend/storage/page/bufpage.c,v 1.75 2007/09/21 21:25:42 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -40,11 +40,12 @@ PageInit(Page page, Size pageSize, Size specialSize)
/* Make sure all fields of page are zero, as well as unused space */
MemSet(p, 0, pageSize);
/* p->pd_flags = 0; done by above MemSet */
/* p->pd_flags = 0; done by above MemSet */
p->pd_lower = SizeOfPageHeaderData;
p->pd_upper = pageSize - specialSize;
p->pd_special = pageSize - specialSize;
PageSetPageSizeAndVersion(page, pageSize, PG_PAGE_LAYOUT_VERSION);
/* p->pd_prune_xid = InvalidTransactionId; done by above MemSet */
}

4
src/include/catalog/catversion.h
View File

@ -37,7 +37,7 @@
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.426 2007/09/20 17:56:32 tgl Exp $
* $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.427 2007/09/21 21:25:42 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -53,6 +53,6 @@
*/
/* yyyymmddN */
#define CATALOG_VERSION_NO 200709201
#define CATALOG_VERSION_NO 200709211
#endif

45
src/include/storage/bufpage.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/storage/bufpage.h,v 1.74 2007/09/20 17:56:32 tgl Exp $
* $PostgreSQL: pgsql/src/include/storage/bufpage.h,v 1.75 2007/09/21 21:25:42 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -48,7 +48,7 @@
*
* EXCEPTIONS:
*
* obviously, a page is not formatted before it is initialized with by
* obviously, a page is not formatted before it is initialized by
* a call to PageInit.
*
* NOTES:
@ -95,6 +95,7 @@ typedef uint16 LocationIndex;
* pd_upper - offset to end of free space.
* pd_special - offset to start of special space.
* pd_pagesize_version - size in bytes and page layout version number.
* pd_prune_xid - oldest XID among potentially prunable tuples on page.
*
* The LSN is used by the buffer manager to enforce the basic rule of WAL:
* "thou shalt write xlog before data". A dirty buffer cannot be dumped
@ -103,6 +104,9 @@ typedef uint16 LocationIndex;
* purposes (it is not clear that this is actually necessary, but it seems
* like a good idea).
*
* pd_prune_xid is a hint field that helps determine whether pruning will be
* useful. It is currently unused in index pages.
*
* The page version number and page size are packed together into a single
* uint16 field. This is for historical reasons: before PostgreSQL 7.3,
* there was no concept of a page version number, and doing it this way
@ -128,6 +132,7 @@ typedef struct PageHeaderData
LocationIndex pd_upper; /* offset to end of free space */
LocationIndex pd_special; /* offset to start of special space */
uint16 pd_pagesize_version;
TransactionId pd_prune_xid; /* oldest prunable XID, or zero if none */
ItemIdData pd_linp[1]; /* beginning of line pointer array */
} PageHeaderData;
@ -141,20 +146,14 @@ typedef PageHeaderData *PageHeader;
* pd_lower. This should be considered a hint rather than the truth, since
* changes to it are not WAL-logged.
*
* PD_PRUNABLE is set if there are any prunable tuples in the page.
* This should be considered a hint rather than the truth, since
* the transaction which generates a prunable tuple may or may not commit.
* Also there is a lag before a tuple is declared dead.
*
* PD_PAGE_FULL is set if an UPDATE doesn't find enough free space in the
* page for its new tuple version; this suggests that a prune is needed.
* Again, this is just a hint.
*/
#define PD_HAS_FREE_LINES 0x0001 /* are there any unused line pointers? */
#define PD_PRUNABLE 0x0002 /* are there any prunable tuples? */
#define PD_PAGE_FULL 0x0004 /* not enough free space for new tuple? */
#define PD_PAGE_FULL 0x0002 /* not enough free space for new tuple? */
#define PD_VALID_FLAG_BITS 0x0007 /* OR of all valid pd_flags bits */
#define PD_VALID_FLAG_BITS 0x0003 /* OR of all valid pd_flags bits */
/*
* Page layout version number 0 is for pre-7.3 Postgres releases.
@ -162,7 +161,8 @@ typedef PageHeaderData *PageHeader;
* Release 8.0 uses 2; it changed the HeapTupleHeader layout again.
* Release 8.1 uses 3; it redefined HeapTupleHeader infomask bits.
* Release 8.3 uses 4; it changed the HeapTupleHeader layout again, and
* added the pd_flags field (by stealing some bits from pd_tli).
* added the pd_flags field (by stealing some bits from pd_tli),
* as well as adding the pd_prune_xid field (which enlarges the header).
*/
#define PG_PAGE_LAYOUT_VERSION 4
@ -348,13 +348,6 @@ typedef PageHeaderData *PageHeader;
#define PageClearHasFreeLinePointers(page) \
(((PageHeader) (page))->pd_flags &= ~PD_HAS_FREE_LINES)
#define PageIsPrunable(page) \
(((PageHeader) (page))->pd_flags & PD_PRUNABLE)
#define PageSetPrunable(page) \
(((PageHeader) (page))->pd_flags |= PD_PRUNABLE)
#define PageClearPrunable(page) \
(((PageHeader) (page))->pd_flags &= ~PD_PRUNABLE)
#define PageIsFull(page) \
(((PageHeader) (page))->pd_flags & PD_PAGE_FULL)
#define PageSetFull(page) \
@ -362,6 +355,22 @@ typedef PageHeaderData *PageHeader;
#define PageClearFull(page) \
(((PageHeader) (page))->pd_flags &= ~PD_PAGE_FULL)
#define PageIsPrunable(page, oldestxmin) \
( \
AssertMacro(TransactionIdIsNormal(oldestxmin)), \
TransactionIdIsValid(((PageHeader) (page))->pd_prune_xid) && \
TransactionIdPrecedes(((PageHeader) (page))->pd_prune_xid, oldestxmin) \
)
#define PageSetPrunable(page, xid) \
do { \
Assert(TransactionIdIsNormal(xid)); \
if (!TransactionIdIsValid(((PageHeader) (page))->pd_prune_xid) || \
TransactionIdPrecedes(xid, ((PageHeader) (page))->pd_prune_xid)) \
((PageHeader) (page))->pd_prune_xid = (xid); \
} while (0)
#define PageClearPrunable(page) \
(((PageHeader) (page))->pd_prune_xid = InvalidTransactionId)
/* ----------------------------------------------------------------
* extern declarations