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bbbc00af88
SI messages now include the relevant database OID, so that operations in one database do not cause useless cache flushes in backends attached to other databases. Declare SI messages properly using a union, to eliminate the former assumption that Oid is the same size as int or Index. Rewrite the nearly-unreadable code in inval.c, and document it better. Arrange for catcache flushes at end of command/transaction to happen before relcache flushes do --- this avoids loading a new tuple into the catcache while setting up new relcache entry, only to have it be flushed again immediately. |
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| .. | ||
| ipc.c | ||
| ipci.c | ||
| Makefile | ||
| README | ||
| shmem.c | ||
| shmqueue.c | ||
| sinval.c | ||
| sinvaladt.c | ||
| spin.c | ||
$Header: /cvsroot/pgsql/src/backend/storage/ipc/README,v 1.1.1.1 1996/07/09 06:21:54 scrappy 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 noticed 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. Access to this shared message buffer is synchronized by the lock manager. The lock manager treats the buffer as a regular relation and sets relation level locks (with mode = LockWait) to block backends while another backend is writing or reading the buffer. The identifiers used for this special 'relation' are database id = 0 and relation id = 0. The current implementation prints regular (e)log information when a message has been removed from the buffer because the buffer is full, and a backend has to reset its cache state. The elog level is NOTICE. This can be used to improve teh behavior of backends when invalidating or reseting their cache state.