Return-Path: owner-postman Received: from localhost (localhost [127.0.0.1]) by nobozo.CS.Berkeley.EDU (8.6.4/8.6.3) with SMTP id TAA11303 for postgres-redist; Mon, 30 May 1994 19:53:13 -0700 Resent-From: POSTGRES mailing list Resent-Message-Id: <199405310253.TAA11303@nobozo.CS.Berkeley.EDU> Sender: owner-postman@postgres.Berkeley.EDU X-Return-Path: owner-postman Received: from faerie.CS.Berkeley.EDU (faerie.CS.Berkeley.EDU [128.32.149.14]) by nobozo.CS.Berkeley.EDU (8.6.4/8.6.3) with ESMTP id TAA11293 for ; Mon, 30 May 1994 19:53:13 -0700 Received: from localhost (localhost [127.0.0.1]) by faerie.CS.Berkeley.EDU (8.6.4/8.1B) with SMTP id TAA20627; Mon, 30 May 1994 19:53:06 -0700 Message-Id: <199405310253.TAA20627@faerie.CS.Berkeley.EDU> X-Authentication-Warning: faerie.CS.Berkeley.EDU: Host localhost didn't use HELO protocol From: aoki@postgres.Berkeley.EDU (Paul M. Aoki) To: Michael Ubell Cc: Mark Metson , postgres@postgres.Berkeley.EDU Subject: locking [was: Use by a Business] Reply-To: aoki@postgres.Berkeley.EDU (Paul M. Aoki) In-reply-to: Your message of Mon, 30 May 94 12:47:38 -0700 <9405301947.AA02892@pigpen.montage.com> Date: Mon, 30 May 94 19:53:06 -0700 X-Sender: aoki@postgres.Berkeley.EDU Resent-To: postgres-redist@postgres.Berkeley.EDU X-Mts: smtp Resent-Date: Mon, 30 May 94 19:53:13 -0700 Resent-XMts: smtp Michael Ubell writes: > > it does do page-level locking for b-trees but not for r-trees and heaps. > Doing page locking on b-trees but not on the underlying heap does not really > buy you anything since if you do an update the whole heap table is locked so > things will be single threaded no matter what you do in the b-tree. well, yes. to quote src/doc/implementation/am.me, written by mike olson (now at montage): Users of the access method interface routines need not worry about locking. The access method routines acquire (and, when appropriate, release) locks on relations in response to scans and updates. Heap relations are protected by two-phase relation level locks. Btree indices use Lehman-Yao5 short-term locking for high concurrency, but since the underlying relations are locked at the relation level, index updates are serialized. Rtree indices use two- phase relation-level locking. 5 Lehman, P., Yao, S., ``Efficient Locking for Concurrent Operations on B-trees'', ACM Transactions on Database Sys- tems, 6(4), December 1981. but having working b-link trees reduces the amount of work some hypothetical person would have to do to convert the core system to page-level locking. (not that the last two messages have had anything to do with what the guy was asking..) -- Paul M. Aoki | CS Div., Dept. of EECS, UCB | aoki@postgres.Berkeley.EDU | Berkeley, CA 94720 | ...!uunet!ucbvax!aoki ============================================================================== To add/remove yourself to/from the POSTGRES mailing list: send mail with the subject line ADD or DEL to "postgres-request@postgres.Berkeley.EDU" If this fails, send mail to "post_questions@postgres.Berkeley.EDU" and a human will deal with it. DO NOT post to the "postgres" mailing list. ==============================================================================