From: Eric Wong <e@yhbt.net>
Date: Wed, 1 Jul 2020 21:06:19 +0000 (+0000)
Subject: overidx: document why we don't use SQLite WAL
X-Git-Tag: v1.6.0~305
X-Git-Url: http://www.git.stargrave.org/?a=commitdiff_plain;h=9ccff7954bf4209babc3d4b0d95b5b933d945ba2;p=public-inbox.git

overidx: document why we don't use SQLite WAL

I was wondering about this myself the other day and had to read
up on it.  So make a note of it for future readers.
---

diff --git a/lib/PublicInbox/OverIdx.pm b/lib/PublicInbox/OverIdx.pm
index c7f45a6c..008a5d1a 100644
--- a/lib/PublicInbox/OverIdx.pm
+++ b/lib/PublicInbox/OverIdx.pm
@@ -23,6 +23,8 @@ sub dbh_new {
 	my $dbh = $self->SUPER::dbh_new(1);
 
 	# TRUNCATE reduces I/O compared to the default (DELETE)
+	# We do not use WAL since we're optimized for read-only ops,
+	# (and read-only requires SQLite 3.22.0 (2018-01-22)).
 	$dbh->do('PRAGMA journal_mode = TRUNCATE');
 
 	# 80000 pages (80MiB on SQLite <3.12.0, 320MiB on 3.12.0+)