From dev-return-321122-archive-asf-public=cust-asf.ponee.io@lucene.apache.org Fri May 4 23:09:06 2018 Return-Path: X-Original-To: archive-asf-public@cust-asf.ponee.io Delivered-To: archive-asf-public@cust-asf.ponee.io Received: from mail.apache.org (hermes.apache.org [140.211.11.3]) by mx-eu-01.ponee.io (Postfix) with SMTP id 611FA180634 for ; Fri, 4 May 2018 23:09:06 +0200 (CEST) Received: (qmail 1880 invoked by uid 500); 4 May 2018 21:09:05 -0000 Mailing-List: contact dev-help@lucene.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: dev@lucene.apache.org Delivered-To: mailing list dev@lucene.apache.org Received: (qmail 1870 invoked by uid 99); 4 May 2018 21:09:05 -0000 Received: from pnap-us-west-generic-nat.apache.org (HELO spamd4-us-west.apache.org) (209.188.14.142) by apache.org (qpsmtpd/0.29) with ESMTP; Fri, 04 May 2018 21:09:05 +0000 Received: from localhost (localhost [127.0.0.1]) by spamd4-us-west.apache.org (ASF Mail Server at spamd4-us-west.apache.org) with ESMTP id 61B79C0678 for ; Fri, 4 May 2018 21:09:04 +0000 (UTC) X-Virus-Scanned: Debian amavisd-new at spamd4-us-west.apache.org X-Spam-Flag: NO X-Spam-Score: -109.511 X-Spam-Level: X-Spam-Status: No, score=-109.511 tagged_above=-999 required=6.31 tests=[ENV_AND_HDR_SPF_MATCH=-0.5, KAM_ASCII_DIVIDERS=0.8, RCVD_IN_DNSWL_MED=-2.3, SPF_PASS=-0.001, T_RP_MATCHES_RCVD=-0.01, USER_IN_DEF_SPF_WL=-7.5, USER_IN_WHITELIST=-100] autolearn=disabled Received: from mx1-lw-eu.apache.org ([10.40.0.8]) by localhost (spamd4-us-west.apache.org [10.40.0.11]) (amavisd-new, port 10024) with ESMTP id YbZommj-nvwu for ; Fri, 4 May 2018 21:09:03 +0000 (UTC) Received: from mailrelay1-us-west.apache.org (mailrelay1-us-west.apache.org [209.188.14.139]) by mx1-lw-eu.apache.org (ASF Mail Server at mx1-lw-eu.apache.org) with ESMTP id 2FAF55F568 for ; Fri, 4 May 2018 21:09:02 +0000 (UTC) Received: from jira-lw-us.apache.org (unknown [207.244.88.139]) by mailrelay1-us-west.apache.org (ASF Mail Server at mailrelay1-us-west.apache.org) with ESMTP id 0073BE12D6 for ; Fri, 4 May 2018 21:09:01 +0000 (UTC) Received: from jira-lw-us.apache.org (localhost [127.0.0.1]) by jira-lw-us.apache.org (ASF Mail Server at jira-lw-us.apache.org) with ESMTP id 690122129E for ; Fri, 4 May 2018 21:09:00 +0000 (UTC) Date: Fri, 4 May 2018 21:09:00 +0000 (UTC) From: "Shawn Heisey (JIRA)" To: dev@lucene.apache.org Message-ID: In-Reply-To: References: Subject: [jira] [Commented] (LUCENE-7976) Make TieredMergePolicy respect maxSegmentSizeMB and allow singleton merges of very large segments MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-JIRA-FingerPrint: 30527f35849b9dde25b450d4833f0394 [ https://issues.apache.org/jira/browse/LUCENE-7976?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16464399#comment-16464399 ] Shawn Heisey commented on LUCENE-7976: -------------------------------------- I have not been following the code, but I have been following the discussion. How much of the complexity is related to not surprising existing users? I think a lot of concerns would disappear if the focus is implementing a new merge policy instead of attempting to fix/augment TMP. [~mikemccand], was TMP a ground-up implementation, or an evolution from LBMP? When I find some time, I can look at the code. I've been on a little bit of a "let's rewrite it from scratch!" kick lately with regards to my own code, so keep that in mind when evaluating any bias I might show! > Make TieredMergePolicy respect maxSegmentSizeMB and allow singleton merges of very large segments > ------------------------------------------------------------------------------------------------- > > Key: LUCENE-7976 > URL: https://issues.apache.org/jira/browse/LUCENE-7976 > Project: Lucene - Core > Issue Type: Improvement > Reporter: Erick Erickson > Assignee: Erick Erickson > Priority: Major > Attachments: LUCENE-7976.patch, LUCENE-7976.patch, LUCENE-7976.patch, LUCENE-7976.patch, LUCENE-7976.patch, LUCENE-7976.patch, LUCENE-7976.patch > > > We're seeing situations "in the wild" where there are very large indexes (on disk) handled quite easily in a single Lucene index. This is particularly true as features like docValues move data into MMapDirectory space. The current TMP algorithm allows on the order of 50% deleted documents as per a dev list conversation with Mike McCandless (and his blog here: https://www.elastic.co/blog/lucenes-handling-of-deleted-documents). > Especially in the current era of very large indexes in aggregate, (think many TB) solutions like "you need to distribute your collection over more shards" become very costly. Additionally, the tempting "optimize" button exacerbates the issue since once you form, say, a 100G segment (by optimizing/forceMerging) it is not eligible for merging until 97.5G of the docs in it are deleted (current default 5G max segment size). > The proposal here would be to add a new parameter to TMP, something like (no, that's not serious name, suggestions welcome) which would default to 100 (or the same behavior we have now). > So if I set this parameter to, say, 20%, and the max segment size stays at 5G, the following would happen when segments were selected for merging: > > any segment with > 20% deleted documents would be merged or rewritten NO MATTER HOW LARGE. There are two cases, > >> the segment has < 5G "live" docs. In that case it would be merged with smaller segments to bring the resulting segment up to 5G. If no smaller segments exist, it would just be rewritten > >> The segment has > 5G "live" docs (the result of a forceMerge or optimize). It would be rewritten into a single segment removing all deleted docs no matter how big it is to start. The 100G example above would be rewritten to an 80G segment for instance. > Of course this would lead to potentially much more I/O which is why the default would be the same behavior we see now. As it stands now, though, there's no way to recover from an optimize/forceMerge except to re-index from scratch. We routinely see 200G-300G Lucene indexes at this point "in the wild" with 10s of shards replicated 3 or more times. And that doesn't even include having these over HDFS. > Alternatives welcome! Something like the above seems minimally invasive. A new merge policy is certainly an alternative. -- This message was sent by Atlassian JIRA (v7.6.3#76005) --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscribe@lucene.apache.org For additional commands, e-mail: dev-help@lucene.apache.org