postgresql

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History

Tom Lane 0a51e7073c Don't take ProcArrayLock while exiting a transaction that has no XID; there is no need for serialization against snapshot-taking because the xact doesn't affect anyone else's snapshot anyway. Per discussion. Also, move various info about the interlocking of transactions and snapshots out of code comments and into a hopefully-more-cohesive discussion in access/transam/README. Also, remove a couple of now-obsolete comments about having to force some WAL to be written to persuade RecordTransactionCommit to do its thing.		2007-09-07 20:59:26 +00:00
..
ipc.c	Suppress warning when compiling with -DPROFILE_PID_DIR: sys/stat.h is	2007-07-25 19:58:56 +00:00
ipci.c	Arrange for large sequential scans to synchronize with each other, so that	2007-06-08 18:23:53 +00:00
Makefile	Remove remains of old depend target.	2007-01-20 17:16:17 +00:00
pmsignal.c	Update CVS HEAD for 2007 copyright. Back branches are typically not	2007-01-05 22:20:05 +00:00
procarray.c	Don't take ProcArrayLock while exiting a transaction that has no XID; there is	2007-09-07 20:59:26 +00:00
README	$Header: -> $PostgreSQL Changes ...	2003-11-29 19:52:15 +00:00
shmem.c	Update CVS HEAD for 2007 copyright. Back branches are typically not	2007-01-05 22:20:05 +00:00
shmqueue.c	Update CVS HEAD for 2007 copyright. Back branches are typically not	2007-01-05 22:20:05 +00:00
sinval.c	Update CVS HEAD for 2007 copyright. Back branches are typically not	2007-01-05 22:20:05 +00:00
sinvaladt.c	Implement lazy XID allocation: transactions that do not modify any database	2007-09-05 18:10:48 +00:00

README

$PostgreSQL: pgsql/src/backend/storage/ipc/README,v 1.4 2003/11/29 19:51:56 pgsql Exp $
Mon Jul 18 11:09:22 PDT 1988  W.KLAS

Cache invalidation synchronization routines:
===========================================

The cache synchronization is done using a message queue. Every
backend can register a message which then has to be read by
all backends. A message read by all backends is removed from the 
queue automatically. If a message has been lost because the buffer
was full, all backends that haven't read this message will be
told that they have to reset their cache state. This is done
at the time when they try to read the message queue.

The message queue is implemented as a shared buffer segment. Actually,
the queue is a circle to allow fast inserting, reading (invalidate data) and
maintaining the buffer.