On 09/11/2015 16:44, Jure Pečar wrote:
On Mon, 09 Nov 2015 12:38:06 +0100
Andrea Brancatelli <abrancate...@schema31.it> wrote:
Well, obviously it the depends on the mail amount.
We have about 1000 mailboxes with about 350GB of online mail. On spike
hours we have a full recycle of the logs in about 10 minutes especially
because of circular replication increasing the server activities.
I ran a separate dbmail imapd instance in order to capture what's happening at
append time. This is the point I found lots of time spent:
Nov 09 17:24:54 email-prod-01.a dbmail-imapd[16154]: [0x7f398a864e30]
Database:[db] db_stmt_prepare(+419): [0x7f398a82cb00] [SELECT seen_flag,
answered_flag, deleted_flag, flagged_flag, draft_flag, recent_flag,
DATE_FORMAT(internal_date, GET_FORMAT(DATETIME,'ISO')), rfcsize, message_idnr
FROM dbmail_messages m LEFT JOIN dbmail_physmessage p ON p.id =
m.physmessage_id WHERE m.mailbox_idnr = ? AND m.status IN (0,1) ORDER BY
message_idnr ASC]
Nov 09 17:24:54 email-prod-01.a dbmail-imapd[16154]: [0x7f398a864e30]
Database:[db] db_stmt_set_u64(+439): [0x7f396400ad70] 1:[27520]
Nov 09 17:25:06 email-prod-01.a dbmail-imapd[16154]: [0x7f398a864e30]
Database:[db] db_con_clear(+298): [0x7f398a82cb00] connection cleared
It's 12 seconds in this case.
Looking at the code I find this statement in dm_mailboxstate.c, function
state_load_messages. Immediately after the query is done, msginfo tree is
filled with the data from the query resut.
It appears this tree insert is the cause of slowness we're observing. Since
this is in GLib code, I'll dig further there. I'll also have to dust off some
trees, insertion and sorting CS theory ;)
Hi,
This slowing down might be able to be refactored out as I'm unsure why,
on inserting a message, a tree of messages is needed. I haven't looked
at the code recently but didn't think dbmail retrieved the messages
before or after an insert.
It's normal for databases to prefer a table scan rather than use an
index when it thinks the number of rows exceeds the benefit of using an
index.
Alan
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