From dev-return-9839-apmail-couchdb-dev-archive=couchdb.apache.org@couchdb.apache.org Tue May 04 05:23:34 2010 Return-Path: Delivered-To: apmail-couchdb-dev-archive@www.apache.org Received: (qmail 693 invoked from network); 4 May 2010 05:23:33 -0000 Received: from unknown (HELO mail.apache.org) (140.211.11.3) by 140.211.11.9 with SMTP; 4 May 2010 05:23:33 -0000 Received: (qmail 39274 invoked by uid 500); 4 May 2010 05:23:33 -0000 Delivered-To: apmail-couchdb-dev-archive@couchdb.apache.org Received: (qmail 39086 invoked by uid 500); 4 May 2010 05:23:33 -0000 Mailing-List: contact dev-help@couchdb.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: dev@couchdb.apache.org Delivered-To: mailing list dev@couchdb.apache.org Received: (qmail 38805 invoked by uid 99); 4 May 2010 05:23:32 -0000 Received: from nike.apache.org (HELO nike.apache.org) (192.87.106.230) by apache.org (qpsmtpd/0.29) with ESMTP; Tue, 04 May 2010 05:23:32 +0000 X-ASF-Spam-Status: No, hits=-2000.0 required=10.0 tests=ALL_TRUSTED X-Spam-Check-By: apache.org Received: from [140.211.11.22] (HELO thor.apache.org) (140.211.11.22) by apache.org (qpsmtpd/0.29) with ESMTP; Tue, 04 May 2010 05:23:18 +0000 Received: from thor (localhost [127.0.0.1]) by thor.apache.org (8.13.8+Sun/8.13.8) with ESMTP id o445MusP006333 for ; Tue, 4 May 2010 05:22:56 GMT Message-ID: <15328595.30451272950576634.JavaMail.jira@thor> Date: Tue, 4 May 2010 01:22:56 -0400 (EDT) From: "Adam Kocoloski (JIRA)" To: dev@couchdb.apache.org Subject: [jira] Updated: (COUCHDB-738) more efficient DB compaction (fewer seeks) In-Reply-To: <18200813.141191271341491073.JavaMail.jira@thor> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-JIRA-FingerPrint: 30527f35849b9dde25b450d4833f0394 X-Virus-Checked: Checked by ClamAV on apache.org [ https://issues.apache.org/jira/browse/COUCHDB-738?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Adam Kocoloski updated COUCHDB-738: ----------------------------------- Attachment: 738-efficient-compaction-v2.patch Here's a new patch which applies cleanly to trunk@940505 and has one important change. In couch_view_updater:load_doc() we call couch_doc:to_doc_info() if we have a #full_doc_info{} record before calling couch_db:open_doc_int(). The reason for this is to skip the rather expensive call to get the entire revision path for the winning revision which shows up in the open_doc_int clause handling #full_doc_info{} records. With this change I get the following timings on a 100 edits/doc DB: MegaView Elapsed time: 5.98 (s) Elapsed time: 5.85 (s) Elapsed time: 4.87 (s) SimpleView Elapsed time: 0.86 (s) Elapsed time: 1.05 (s) Elapsed time: 0.75 (s) Those are essentially identical to the timings I got earlier for trunk. > more efficient DB compaction (fewer seeks) > ------------------------------------------ > > Key: COUCHDB-738 > URL: https://issues.apache.org/jira/browse/COUCHDB-738 > Project: CouchDB > Issue Type: Improvement > Components: Database Core > Affects Versions: 0.9.2, 0.10.1, 0.11 > Reporter: Adam Kocoloski > Assignee: Adam Kocoloski > Fix For: 1.1 > > Attachments: 738-efficient-compaction-v1.patch, 738-efficient-compaction-v2.patch > > > CouchDB's database compaction algorithm walks the by_seq btree, then does a lookup in the by_id btree for every document in the database. It does this because the #full_doc_info{} record with the full revision tree is only stored in the by_id tree. I'm proposing instead to store duplicate copies of #full_doc_info{} in both trees, and to have the compactor use the by_seq tree exclusively. The net effect is significantly fewer calls to pread(), and an compaction IO pattern where reads tend to be clustered close to each other in the file. > If the by_id tree is fully cached, or if the id tree nodes are located near the seq tree nodes, the performance improvement is small but noticeable (~10% in some simple tests). On the other hand, in the worst-case scenario of randomly-generated docids and a database much larger than main memory the improvement is huge. Joe Williams did some simple benchmarks with a 50k document, 600 MB database on a 256MB VPS. The compaction time for that DB dropped from 15m to 2m20s, so more than 6x faster. > Storing the #full_doc_info{} in the seq tree also allows for some similar optimizations in the replicator. > This patch might have downsides when documents have a large number of edits. These include an increase in the size of the database and slower view indexing. I expect both to be small effects. > The patch can be applied directly to trunk@934272. Existing DBs are still readable, new updates will be written in the new format, and databases can be fully upgraded by compacting. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.