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pgsql/ oc/src/sgml/ref/checkpoint.sgml oc/src/ ...

From: Tom Lane <tgl(at)hub(dot)org>
To: pgsql-committers(at)postgresql(dot)org
Subject: pgsql/ oc/src/sgml/ref/checkpoint.sgml oc/src/ ...
Date: 2001-03-13 01:17:07
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-committers
CVSROOT:	/home/projects/pgsql/cvsroot
Module name:	pgsql
Changes by:	tgl(at)hub(dot)org	01/03/12 20:17:06

Modified files:
	doc/src/sgml/ref: checkpoint.sgml 
	doc/src/sgml   : runtime.sgml wal.sgml 
	src/backend/access/transam: transam.c varsup.c xact.c xlog.c 
	src/backend/bootstrap: bootstrap.c 
	src/backend/postmaster: postmaster.c 
	src/backend/storage/ipc: ipc.c 
	src/backend/tcop: postgres.c 
	src/backend/utils/init: globals.c miscinit.c 
	src/backend/utils/misc: guc.c postgresql.conf.sample 
	src/include/access: transam.h xlog.h xlogdefs.h xlogutils.h 
	src/include    : miscadmin.h 
	src/include/tcop: tcopprot.h 
	src/include/storage: ipc.h 
	src/backend/utils/hash: Makefile 
	src/backend/port/beos: shm.c 
	src/backend/port/qnx4: shm.c 
Added files:
	src/include/utils: pg_crc.h 
	src/backend/utils/hash: pg_crc.c 
	src/include/catalog: pg_control.h 

Log message:
	XLOG (and related) changes:
	* Store two past checkpoint locations, not just one, in pg_control.
	On startup, we fall back to the older checkpoint if the newer one
	is unreadable.  Also, a physical copy of the newest checkpoint record
	is kept in pg_control for possible use in disaster recovery (ie,
	complete loss of pg_xlog).  Also add a version number for pg_control
	itself.  Remove archdir from pg_control; it ought to be a GUC
	parameter, not a special case (not that it's implemented yet anyway).
	* Suppress successive checkpoint records when nothing has been entered
	in the WAL log since the last one.  This is not so much to avoid I/O
	as to make it actually useful to keep track of the last two
	checkpoints.  If the things are right next to each other then there's
	not a lot of redundancy gained...
	* Change CRC scheme to a true 64-bit CRC, not a pair of 32-bit CRCs
	on alternate bytes.  Polynomial borrowed from ECMA DLT1 standard.
	* Fix XLOG record length handling so that it will work at BLCKSZ = 32k.
	* Change XID allocation to work more like OID allocation.  (This is of
	dubious necessity, but I think it's a good idea anyway.)
	* Fix a number of minor bugs, such as off-by-one logic for XLOG file
	wraparound at the 4 gig mark.
	* Add documentation and clean up some coding infelicities; move file
	format declarations out to include files where planned contrib
	utilities can get at them.
	* Checkpoint will now occur every CHECKPOINT_SEGMENTS log segments or
	every CHECKPOINT_TIMEOUT seconds, whichever comes first.  It is also
	possible to force a checkpoint by sending SIGUSR1 to the postmaster
	(undocumented feature...)
	* Defend against kill -9 postmaster by storing shmem block's key and ID
	in lockfile, and checking at startup to ensure that no
	processes are still connected to old shmem block (if it still exists).
	* Switch backends to accept SIGQUIT rather than SIGUSR1 for emergency
	stop, for symmetry with postmaster and xlog utilities.  Clean up signal
	handling in bootstrap.c so that xlog utilities launched by postmaster
	will react to signals better.
	* Standalone bootstrap now grabs lockfile in target directory, as added
	insurance against running it in parallel with live postmaster.

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