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e0c9301c87
do anything yet, but it has the necessary connections to initialization and so forth. Make some gestures towards allowing number of blocks in a relation to be BlockNumber, ie, unsigned int, rather than signed int. (I doubt I got all the places that are sloppy about it, yet.) On the way, replace the hardwired NLOCKS_PER_XACT fudge factor with a GUC variable.
$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.