user/dev discussion of public-inbox itself
 help / color / mirror / code / Atom feed
From: Eric Wong <e@80x24.org>
To: meta@public-inbox.org
Subject: [PATCH v2 2/6] lei_mail_sync: don't hold statement handle into callback
Date: Thu, 16 Sep 2021 20:56:40 -0500	[thread overview]
Message-ID: <20210917015644.32746-3-e@80x24.org> (raw)
In-Reply-To: <20210917015644.32746-1-e@80x24.org>

This can cause readers and writers to conflict since the
implicit transaction from SELECT in a LeiRefreshMailSync
worker would block the LeiStore process.
---
 lib/PublicInbox/LeiMailSync.pm | 41 ++++++++++++++++++++++++++--------
 1 file changed, 32 insertions(+), 9 deletions(-)

diff --git a/lib/PublicInbox/LeiMailSync.pm b/lib/PublicInbox/LeiMailSync.pm
index 5a10c127..8f584ccb 100644
--- a/lib/PublicInbox/LeiMailSync.pm
+++ b/lib/PublicInbox/LeiMailSync.pm
@@ -169,22 +169,45 @@ INSERT OR IGNORE INTO blob2name (oidbin, fid, name) VALUES (?, ?, ?)
 sub each_src {
 	my ($self, $folder, $cb, @args) = @_;
 	my $dbh = $self->{dbh} //= dbh_new($self);
-	my ($fid, $sth);
+	my $fid;
 	if (ref($folder) eq 'HASH') {
 		$fid = $folder->{fid} // die "BUG: no `fid'";
 	} else {
 		$fid = $self->{fmap}->{$folder} //=
 			fid_for($self, $folder) // return;
 	}
-	$sth = $dbh->prepare('SELECT oidbin,uid FROM blob2num WHERE fid = ?');
-	$sth->execute($fid);
-	while (my ($oidbin, $id) = $sth->fetchrow_array) {
-		$cb->($oidbin, $id, @args);
+
+	# minimize implicit txn time to avoid blocking writers by
+	# batching SELECTs.  This looks wonky but is necessary since
+	# $cb-> may access the DB on its own.
+	my $ary = $dbh->selectall_arrayref(<<'', undef, $fid);
+SELECT _rowid_,oidbin,uid FROM blob2num WHERE fid = ?
+ORDER BY _rowid_ ASC LIMIT 1000
+
+	my $min = @$ary ? $ary->[-1]->[0] : undef;
+	while (defined $min) {
+		for my $row (@$ary) { $cb->($row->[1], $row->[2], @args) }
+
+		$ary = $dbh->selectall_arrayref(<<'', undef, $fid, $min);
+SELECT _rowid_,oidbin,uid FROM blob2num WHERE fid = ? AND _rowid_ > ?
+ORDER BY _rowid_ ASC LIMIT 1000
+
+		$min = @$ary ? $ary->[-1]->[0] : undef;
 	}
-	$sth = $dbh->prepare('SELECT oidbin,name FROM blob2name WHERE fid = ?');
-	$sth->execute($fid);
-	while (my ($oidbin, $id) = $sth->fetchrow_array) {
-		$cb->($oidbin, \$id, @args);
+
+	$ary = $dbh->selectall_arrayref(<<'', undef, $fid);
+SELECT _rowid_,oidbin,name FROM blob2name WHERE fid = ?
+ORDER BY _rowid_ ASC LIMIT 1000
+
+	$min = @$ary ? $ary->[-1]->[0] : undef;
+	while (defined $min) {
+		for my $row (@$ary) { $cb->($row->[1], \($row->[2]), @args) }
+
+		$ary = $dbh->selectall_arrayref(<<'', undef, $fid, $min);
+SELECT _rowid_,oidbin,name FROM blob2name WHERE fid = ? AND _rowid_ > ?
+ORDER BY _rowid_ ASC LIMIT 1000
+
+		$min = @$ary ? $ary->[-1]->[0] : undef;
 	}
 }
 

  parent reply	other threads:[~2021-09-17  1:56 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-17  1:56 [PATCH v2 0/6] lei refresh-mail-sync: another try Eric Wong
2021-09-17  1:56 ` [PATCH v2 1/6] lei refresh-mail-sync: replace prune-mail-sync Eric Wong
2021-09-17  1:56 ` Eric Wong [this message]
2021-09-17  1:56 ` [PATCH v2 3/6] lei refresh-mail-sync: remove "gone" notices Eric Wong
2021-09-17  1:56 ` [PATCH v2 4/6] lei refresh-mail-sync: drop unused {verify} code path Eric Wong
2021-09-17  1:56 ` [PATCH v2 5/6] lei refresh-mail-sync: implicitly remove missing folders Eric Wong
2021-09-17  1:56 ` [PATCH v2 6/6] lei refresh-mail-sync: drop old IMAP folder info Eric Wong

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

  List information: https://public-inbox.org/README

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210917015644.32746-3-e@80x24.org \
    --to=e@80x24.org \
    --cc=meta@public-inbox.org \
    --subject='Re: [PATCH v2 2/6] lei_mail_sync: don'\''t hold statement handle into callback' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Code repositories for project(s) associated with this inbox:

	https://80x24.org/public-inbox.git

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).