mirror of
https://github.com/postgres/postgres.git
synced 2025-11-16 15:02:33 +03:00
48188e1621
in PITR scenarios. We now WAL-log the replacement of old XIDs with FrozenTransactionId, so that such replacement is guaranteed to propagate to PITR slave databases. Also, rather than relying on hint-bit updates to be preserved, pg_clog is not truncated until all instances of an XID are known to have been replaced by FrozenTransactionId. Add new GUC variables and pg_autovacuum columns to allow management of the freezing policy, so that users can trade off the size of pg_clog against the amount of freezing work done. Revise the already-existing code that forces autovacuum of tables approaching the wraparound point to make it more bulletproof; also, revise the autovacuum logic so that anti-wraparound vacuuming is done per-table rather than per-database. initdb forced because of changes in pg_class, pg_database, and pg_autovacuum catalogs. Heikki Linnakangas, Simon Riggs, and Tom Lane.
$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.