Received: from maia.hub.org (maia-3.hub.org [200.46.204.243]) by mail.postgresql.org (Postfix) with ESMTP id E5BBC1337BFA for ; Fri, 18 Mar 2011 02:45:53 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.243]) (amavisd-maia, port 10024) with ESMTP id 12039-07 for ; Fri, 18 Mar 2011 05:45:46 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mail-ww0-f50.google.com (mail-ww0-f50.google.com [74.125.82.50]) by mail.postgresql.org (Postfix) with ESMTP id C18B01337BF8 for ; Fri, 18 Mar 2011 02:45:45 -0300 (ADT) Received: by wwc33 with SMTP id 33so4484351wwc.19 for ; Thu, 17 Mar 2011 22:45:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type :content-transfer-encoding; bh=Gtu8lz+udR9vyZjQXK/vvAYgvVczKC1AlP4vBsamTU8=; b=wb82xSiRXBMhit0OQ5BOw9dqVHZQbvAbHoIqwd3iJuto+m8cCHvO7YJpdmTbEs3oHY UaBcbbmL72mvvIPb6j4a0wj6H3gqPmob2Sc+h3Bu80eJf351Q5BTH+glUzwYYcbHkoOI /ks8cgmUxOq2iAKbbWsoJAAzCqe2XTte98cKQ= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=w3QUn2lv/s21r09ZPxHE4W1NxIFLXW1g/qgPz9TIa9IT7cSAq2Fv4ji1tYXwB9shkX IT+xw6J+5KDbpoUcj76cjwRM7aKURiaTswYGp3BW3EAcFMiNYMHSEa/ZN93X3BynKaum KOyDYZr9dz7g78LBPXU5wvOyuQ6PgFMq+b49c= MIME-Version: 1.0 Received: by 10.216.24.132 with SMTP id x4mr1937336wex.81.1300427144318; Thu, 17 Mar 2011 22:45:44 -0700 (PDT) Received: by 10.216.154.18 with HTTP; Thu, 17 Mar 2011 22:45:44 -0700 (PDT) In-Reply-To: References: Date: Fri, 18 Mar 2011 14:45:44 +0900 Message-ID: Subject: Re: [COMMITTERS] pgsql: Efficient transaction-controlled synchronous replication. From: Fujii Masao To: Robert Haas Cc: Simon Riggs , PostgreSQL-development Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=1.72 tagged_above=-5 required=5 tests=BAYES_00=-1.9, FREEMAIL_FROM=0.001, FS_REPLICA=3.599, RCVD_IN_DNSWL_LOW=-0.7, SARE_SPEC_REPLICA=0.72 X-Spam-Level: * X-Archive-Number: 201103/1097 X-Sequence-Number: 184347 On Fri, Mar 18, 2011 at 2:52 AM, Robert Haas wrote: > On Thu, Mar 10, 2011 at 3:04 PM, Robert Haas wrot= e: >>> - =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 /* Let the master know th= at we received some data. */ >>> - =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 XLogWalRcvSendReply(); >>> - =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 XLogWalRcvSendHSFeedback(= ); >>> >>> This change completely eliminates the difference between write_location >>> and flush_location in pg_stat_replication. If this change is reasoable,= we >>> should get rid of write_location from pg_stat_replication since it's us= eless. >>> If not, this change should be reverted. I'm not sure whether monitoring >>> the difference between write and flush locations is useful. But I guess= that >>> someone thought so and that code was added. >> >> I could go either way on this but clearly we need to do one or the other= . > > I'm not really sure why this was part of the synchronous replication > patch, but after mulling it over I think it's probably right to rip > out write_location completely. =A0There shouldn't ordinarily be much of > a gap between write location and flush location, so it's probably not > worth the extra network overhead to keep track of it. =A0We might need > to re-add some form of this in the future if we have a version of > synchronous replication that only waits for confirmation of receipt > rather than for confirmation of flush, but we don't have that in 9.1, > so why bother? > > Barring objections, I'll go do that. I agree to get rid of write_location. Regards, --=20 Fujii Masao NIPPON TELEGRAPH AND TELEPHONE CORPORATION NTT Open Source Software Center