From: Timo Sirainen <timo.sirainen@open-xchange.com>
Date: Thu, 3 Feb 2022 18:59:05 +0000 (+0100)
Subject: imap: Add comment explaining EXPUNGE batching
X-Git-Tag: 2.4.0~4379
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=12016539558c4bd148e2aea86342bdfe6f66d12f;p=thirdparty%2Fdovecot%2Fcore.git

imap: Add comment explaining EXPUNGE batching
---

diff --git a/src/imap/imap-expunge.c b/src/imap/imap-expunge.c
index ff1a2134e8..9a5bafed4f 100644
--- a/src/imap/imap-expunge.c
+++ b/src/imap/imap-expunge.c
@@ -73,6 +73,20 @@ int imap_expunge(struct mailbox *box, struct mail_search_arg *next_search_arg,
 		return -1;
 	}
 
+	/* NOTE: This batching mainly helps when lazy_expunge is used. Without
+	   it, it just quickly writes a bunch of expunge transactions. The
+	   actual email deletion is done afterwards in mailbox_sync() for all
+	   of the mails. This isn't ideal, but alternatives are a bit tricky
+	   because mailbox_sync() can't be called for the SELECTed mailbox.
+
+	   a) Simpler fix would be to open a new mailbox view which can be
+	   synced, but this causes imapc to open another IMAP connection.
+	   Although if it's done only for large expunge transactions it would
+	   be less of an issue.
+
+	   b) The caller would have to do batching and sync the mailbox
+	   multiple times. This would require a new kind of cmd_sync() that
+	   would send untagged replies but not the tagged reply. */
 	seqset_iter = imap_search_seqset_iter_init(search_args, status.messages,
 						   IMAP_EXPUNGE_BATCH_SIZE);