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Support an optional asynchronous commit mode, in which we don't flush WAL

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before reporting a transaction committed.  Data consistency is still
guaranteed (unlike setting fsync = off), but a crash may lose the effects
of the last few transactions.  Patch by Simon, some editorialization by Tom.
This commit is contained in:
Tom Lane
2007-08-01 22:45:09 +00:00
parent c722628a43
commit 4a78cdeb6b
25 changed files with 998 additions and 303 deletions
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25
src/include/access/slru.h
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@@ -6,13 +6,14 @@
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/access/slru.h,v 1.20 2007/01/05 22:19:51 momjian Exp $
* $PostgreSQL: pgsql/src/include/access/slru.h,v 1.21 2007/08/01 22:45:09 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#ifndef SLRU_H
#define SLRU_H
#include "access/xlogdefs.h"
#include "storage/lwlock.h"
@@ -51,6 +52,17 @@ typedef struct SlruSharedData
int *page_lru_count;
LWLockId *buffer_locks;
/*
* Optional array of WAL flush LSNs associated with entries in the SLRU
* pages. If not zero/NULL, we must flush WAL before writing pages (true
* for pg_clog, false for multixact and pg_subtrans). group_lsn[] has
* lsn_groups_per_page entries per buffer slot, each containing the
* highest LSN known for a contiguous group of SLRU entries on that slot's
* page.
*/
XLogRecPtr *group_lsn;
int lsn_groups_per_page;
/*----------
* We mark a page "most recently used" by setting
* page_lru_count[slotno] = ++cur_lru_count;
@@ -81,8 +93,8 @@ typedef struct SlruCtlData
SlruShared shared;
/*
* This flag tells whether to fsync writes (true for pg_clog, false for
* pg_subtrans).
* This flag tells whether to fsync writes (true for pg_clog and multixact
* stuff, false for pg_subtrans).
*/
bool do_fsync;
@@ -106,11 +118,12 @@ typedef SlruCtlData *SlruCtl;
typedef struct SlruFlushData *SlruFlush;
extern Size SimpleLruShmemSize(int nslots);
extern void SimpleLruInit(SlruCtl ctl, const char *name, int nslots,
extern Size SimpleLruShmemSize(int nslots, int nlsns);
extern void SimpleLruInit(SlruCtl ctl, const char *name, int nslots, int nlsns,
LWLockId ctllock, const char *subdir);
extern int SimpleLruZeroPage(SlruCtl ctl, int pageno);
extern int SimpleLruReadPage(SlruCtl ctl, int pageno, TransactionId xid);
extern int SimpleLruReadPage(SlruCtl ctl, int pageno, bool write_ok,
TransactionId xid);
extern int SimpleLruReadPage_ReadOnly(SlruCtl ctl, int pageno,
TransactionId xid);
extern void SimpleLruWritePage(SlruCtl ctl, int slotno, SlruFlush fdata);