database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-02 09:02:37 +03:00
Code Activity

Rewrite btree vacuuming to fold the former bulkdelete and cleanup operations

Browse Source 
into a single mostly-physical-order scan of the index.  This requires some
ticklish interlocking considerations, but should create no material
performance impact on normal index operations (at least given the
already-committed changes to make scans work a page at a time).  VACUUM
itself should get significantly faster in any index that's degenerated to a
very nonlinear page order.  Also, we save one pass over the index entirely,
except in the case where there were no deletions to do and so only one pass
happened anyway.

Original patch by Heikki Linnakangas, rework by Tom Lane.
This commit is contained in:
Tom Lane
2006-05-08 00:00:17 +00:00
parent 09cb5c0e7d
commit 5749f6ef0c
10 changed files with 692 additions and 253 deletions
Download Patch File Download Diff File Expand all files Collapse all files

23
src/include/access/nbtree.h
View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/access/nbtree.h,v 1.97 2006/05/07 01:21:30 tgl Exp $
* $PostgreSQL: pgsql/src/include/access/nbtree.h,v 1.98 2006/05/08 00:00:10 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -19,6 +19,10 @@
#include "access/sdir.h"
#include "access/xlogutils.h"
/* There's room for a 16-bit vacuum cycle ID in BTPageOpaqueData */
typedef uint16 BTCycleId;
/*
* BTPageOpaqueData -- At the end of every page, we store a pointer
* to both siblings in the tree. This is used to do forward/backward
@ -31,6 +35,16 @@
* and status. If the page is deleted, we replace the level with the
* next-transaction-ID value indicating when it is safe to reclaim the page.
*
* We also store a "vacuum cycle ID". When a page is split while VACUUM is
* processing the index, a nonzero value associated with the VACUUM run is
* stored into both halves of the split page. (If VACUUM is not running,
* both pages receive zero cycleids.) This allows VACUUM to detect whether
* a page was split since it started, with a small probability of false match
* if the page was last split some exact multiple of 65536 VACUUMs ago.
* Also, during a split, the BTP_SPLIT_END flag is cleared in the left
* (original) page, and set in the right page, but only if the next page
* to its right has a different cycleid.
*
* NOTE: the BTP_LEAF flag bit is redundant since level==0 could be tested
* instead.
*/
@ -45,6 +59,7 @@ typedef struct BTPageOpaqueData
TransactionId xact; /* next transaction ID, if deleted */
} btpo;
uint16 btpo_flags; /* flag bits, see below */
BTCycleId btpo_cycleid; /* vacuum cycle ID of latest split */
} BTPageOpaqueData;
typedef BTPageOpaqueData *BTPageOpaque;
@ -55,6 +70,7 @@ typedef BTPageOpaqueData *BTPageOpaque;
#define BTP_DELETED (1 << 2) /* page has been deleted from tree */
#define BTP_META (1 << 3) /* meta-page */
#define BTP_HALF_DEAD (1 << 4) /* empty, but still in tree */
#define BTP_SPLIT_END (1 << 5) /* rightmost page of split group */
/*
@ -492,6 +508,11 @@ extern bool _bt_checkkeys(IndexScanDesc scan,
Page page, OffsetNumber offnum,
ScanDirection dir, bool *continuescan);
extern void _bt_killitems(IndexScanDesc scan, bool haveLock);
extern BTCycleId _bt_vacuum_cycleid(Relation rel);
extern BTCycleId _bt_start_vacuum(Relation rel);
extern void _bt_end_vacuum(Relation rel);
extern Size BTreeShmemSize(void);
extern void BTreeShmemInit(void);
/*
* prototypes for functions in nbtsort.c