[rt-users] slow join with cachedgroupmembers for a simple "comment" click
David Gwynne
david at gwynne.id.au
Wed Feb 3 18:48:35 EST 2016
> On 4 Feb 2016, at 00:08, Palle Girgensohn <girgen at pingpong.net> wrote:
>
> Hi David,
>
> Thanks for this input.
>
> it takes the query from 1 minute+ (== timeout in fcgid) to subseond.
>
> Big leap forward!
>
> Thanks!
>
>
> The two queries you posted are equally fast for me, ~ 8 ms, but render different result, 15 vs 16 rows. :-(
yeah, after i sent it i recognised some issues with mine. i can fix it, but then id have to go back and make RT generate the query and that idea makes me sad.
if there's interest i can fix my query, but only if it'll help someone else.
>
> Palle
>
>
>
>> 3 feb. 2016 kl. 13:39 skrev David Gwynne <david at gwynne.id.au>:
>>
>> On Thu, Jan 07, 2016 at 01:57:46PM +0100, Palle Girgensohn wrote:
>>> Hi,
>>>
>>> For our RT database, just clicking "comment" takes five seconds. In general, RT is very slow for us, and I believe that after 10+ years of use, we have bloat in the database. 500k+ entries in CachedGroupMembers, for example. All of them but a handful are enabled (disabled = 0).
>>>
>>> So when I click comment in a ticket, I wait for this query five seconds. Seems to me it produces a list of users allowed to comment on this.
>>>
>>> The results can be very different for different queus.
>>>
>>> We'd like to keep the history, so shredding old tickets is not the first choice for us.
>>>
>>>
>>>
>>> rt=# explain ANALYZE
>>> rt-# SELECT DISTINCT main.id,
>>> rt-# main.name
>>> rt-# FROM Users main
>>> rt-# CROSS JOIN ACL ACL_3
>>> rt-# JOIN Principals Principals_1 ON (Principals_1.id = main.id)
>>> rt-# JOIN CachedGroupMembers CachedGroupMembers_2 ON (CachedGroupMembers_2.MemberId = Principals_1.id)
>>> rt-# JOIN CachedGroupMembers CachedGroupMembers_4 ON (CachedGroupMembers_4.MemberId = Principals_1.id)
>>> rt-# WHERE ((ACL_3.ObjectType = 'RT::Ticket'
>>> rt(# AND ACL_3.ObjectId = 75164)
>>> rt(# OR (ACL_3.ObjectType = 'RT::Queue'
>>> rt(# AND ACL_3.ObjectId = 21)
>>> rt(# OR (ACL_3.ObjectType = 'RT::System'
>>> rt(# AND ACL_3.ObjectId = 1))
>>> rt-# AND (ACL_3.PrincipalId = CachedGroupMembers_4.GroupId)
>>> rt-# AND (ACL_3.PrincipalType = 'Group')
>>> rt-# AND (ACL_3.RightName = 'OwnTicket')
>>> rt-# AND (CachedGroupMembers_2.Disabled = '0')
>>> rt-# AND (CachedGroupMembers_2.GroupId = '4')
>>> rt-# AND (CachedGroupMembers_4.Disabled = '0')
>>> rt-# AND (Principals_1.Disabled = '0')
>>> rt-# AND (Principals_1.PrincipalType = 'User')
>>> rt-# AND (Principals_1.id != '1')
>>> rt-# ORDER BY main.Name ASC;
>>> QUERY PLAN
>>> --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>>> Unique (cost=554.36..554.37 rows=1 width=29) (actual time=5927.879..5927.937 rows=72 loops=1)
>>> -> Sort (cost=554.36..554.37 rows=1 width=29) (actual time=5927.877..5927.893 rows=149 loops=1)
>>> Sort Key: main.name, main.id
>>> Sort Method: quicksort Memory: 32kB
>>> -> Nested Loop (cost=1.84..554.35 rows=1 width=29) (actual time=5.926..5927.400 rows=149 loops=1)
>>> -> Nested Loop (cost=1.56..550.64 rows=2 width=33) (actual time=0.152..78.279 rows=129788 loops=1)
>>> -> Nested Loop (cost=1.13..548.76 rows=1 width=37) (actual time=0.131..7.133 rows=134 loops=1)
>>> -> Nested Loop (cost=0.71..493.88 rows=36 width=33) (actual time=0.115..4.984 rows=136 loops=1)
>>> -> Index Only Scan using disgroumem on cachedgroupmembers cachedgroupmembers_2 (cost=0.42..5.94 rows=76 width=4) (actual time=0.079..0.152 rows=137 loops=1)
>>> Index Cond: ((groupid = 4) AND (disabled = 0::smallint))
>>> Heap Fetches: 0
>>> -> Index Scan using users_pkey on users main (cost=0.29..6.41 rows=1 width=29) (actual time=0.033..0.034 rows=1 loops=137)
>>> Index Cond: (id = cachedgroupmembers_2.memberid)
>>> -> Index Scan using principals_pkey on principals principals_1 (cost=0.42..1.51 rows=1 width=4) (actual time=0.014..0.015 rows=1 loops=136)
>>> Index Cond: (id = main.id)
>>> Filter: ((id <> 1) AND (disabled = 0::smallint) AND (principaltype = 'User'::text))
>>> Rows Removed by Filter: 0
>>> -> Index Only Scan using cachedgroupmembers2 on cachedgroupmembers cachedgroupmembers_4 (cost=0.42..1.67 rows=21 width=8) (actual time=0.011..0.290 rows=969 loops=134)
>>> Index Cond: ((memberid = principals_1.id) AND (disabled = 0::smallint))
>>> Heap Fetches: 0
>>> -> Index Only Scan using acl1 on acl acl_3 (cost=0.28..1.85 rows=1 width=4) (actual time=0.045..0.045 rows=0 loops=129788)
>>> Index Cond: ((rightname = 'OwnTicket'::text) AND (principaltype = 'Group'::text) AND (principalid = cachedgroupmembers_4.groupid))
>>> Filter: (((objecttype = 'RT::Ticket'::text) AND (objectid = 75164)) OR ((objecttype = 'RT::Queue'::text) AND (objectid = 21)) OR ((objecttype = 'RT::System'::text) AND (objectid = 1)))
>>> Rows Removed by Filter: 0
>>> Heap Fetches: 0
>>> Planning time: 6.461 ms
>>> Execution time: 5928.204 ms
>>> (27 rows)
>>>
>>>
>>>
>>> If I remove the join on CachedGroupMembers_2 (the one that joins on memberid = principals.id where groupid = 4), it is lightning fast.
>>>
>>> rt=# explain ANALYZE
>>> rt-# SELECT DISTINCT main.id,
>>> rt-# main.name
>>> rt-# FROM Users main
>>> rt-# CROSS JOIN ACL ACL_3
>>> rt-# JOIN Principals Principals_1 ON (Principals_1.id = main.id)
>>> rt-# --JOIN CachedGroupMembers CachedGroupMembers_2 ON (CachedGroupMembers_2.MemberId = Principals_1.id)
>>> rt-# JOIN CachedGroupMembers CachedGroupMembers_4 ON (CachedGroupMembers_4.MemberId = Principals_1.id)
>>> rt-# WHERE ((ACL_3.ObjectType = 'RT::Ticket'
>>> rt(# AND ACL_3.ObjectId = 75164)
>>> rt(# OR (ACL_3.ObjectType = 'RT::Queue'
>>> rt(# AND ACL_3.ObjectId = 21)
>>> rt(# OR (ACL_3.ObjectType = 'RT::System'
>>> rt(# AND ACL_3.ObjectId = 1))
>>> rt-# AND (ACL_3.PrincipalId = CachedGroupMembers_4.GroupId)
>>> rt-# AND (ACL_3.PrincipalType = 'Group')
>>> rt-# AND (ACL_3.RightName = 'OwnTicket')
>>> rt-# -- AND (CachedGroupMembers_2.Disabled = '0')
>>> rt-# -- AND (CachedGroupMembers_2.GroupId = '4')
>>> rt-# AND (CachedGroupMembers_4.Disabled = '0')
>>> rt-# AND (Principals_1.Disabled = '0')
>>> rt-# AND (Principals_1.PrincipalType = 'User')
>>> rt-# AND (Principals_1.id != '1')
>>> rt-# ORDER BY main.Name ASC;
>>> QUERY PLAN
>>> --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>>> Unique (cost=1323.30..1323.33 rows=4 width=29) (actual time=20.321..20.395 rows=74 loops=1)
>>> -> Sort (cost=1323.30..1323.31 rows=4 width=29) (actual time=20.320..20.340 rows=108 loops=1)
>>> Sort Key: main.name, main.id
>>> Sort Method: quicksort Memory: 30kB
>>> -> Nested Loop (cost=614.87..1323.26 rows=4 width=29) (actual time=18.323..19.919 rows=108 loops=1)
>>> Join Filter: (main.id = principals_1.id)
>>> -> Hash Join (cost=614.44..724.20 rows=1232 width=33) (actual time=18.305..18.755 rows=124 loops=1)
>>> Hash Cond: (cachedgroupmembers_4.memberid = main.id)
>>> -> Nested Loop (cost=0.71..71.95 rows=2620 width=4) (actual time=0.168..0.456 rows=136 loops=1)
>>> -> Index Only Scan using acl1 on acl acl_3 (cost=0.28..12.31 rows=13 width=4) (actual time=0.149..0.238 rows=12 loops=1)
>>> Index Cond: ((rightname = 'OwnTicket'::text) AND (principaltype = 'Group'::text))
>>> Filter: (((objecttype = 'RT::Ticket'::text) AND (objectid = 75164)) OR ((objecttype = 'RT::Queue'::text) AND (objectid = 21)) OR ((objecttype = 'RT::System'::text) AND (objectid = 1)))
>>> Rows Removed by Filter: 108
>>> Heap Fetches: 0
>>> -> Index Only Scan using disgroumem on cachedgroupmembers cachedgroupmembers_4 (cost=0.42..4.54 rows=5 width=8) (actual time=0.009..0.013 rows=11 loops=12)
>>> Index Cond: ((groupid = acl_3.principalid) AND (disabled = 0::smallint))
>>> Heap Fetches: 0
>>> -> Hash (cost=454.44..454.44 rows=12744 width=29) (actual time=18.118..18.118 rows=12819 loops=1)
>>> Buckets: 2048 Batches: 1 Memory Usage: 771kB
>>> -> Seq Scan on users main (cost=0.00..454.44 rows=12744 width=29) (actual time=0.009..9.680 rows=12819 loops=1)
>>> -> Index Scan using principals_pkey on principals principals_1 (cost=0.42..0.47 rows=1 width=4) (actual time=0.008..0.008 rows=1 loops=124)
>>> Index Cond: (id = cachedgroupmembers_4.memberid)
>>> Filter: ((id <> 1) AND (disabled = 0::smallint) AND (principaltype = 'User'::text))
>>> Rows Removed by Filter: 0
>>> Planning time: 2.446 ms
>>> Execution time: 20.726 ms
>>> (26 rows)
>>>
>>>
>>>
>>> Any ideas how to make RT quicker here? What is the purpose of this query anyway? I'm just getting the comments view?
>>
>> ola,
>>
>> we hit this today while working on updating our installation. another
>> guy figured out that reverting
>> https://github.com/bestpractical/rt/commit/e48b94252c0bb4ab55587515cf695c0300b72d03
>> brings the performance back in line with what we experience with
>> our currently 4.0 install.
>>
>> it takes the query from ~5500ms down to ~110ms
>>
>> however, while he was figuring that out, i was tinkering with the
>> query in psql with the intention of making it fast and then tricking
>> RT into generating the query. the query i ended up with runs in
>> about 8ms.
>>
>> the current (slow) query looks like that for us:
>>
>> SELECT
>> DISTINCT main.*
>> FROM
>> Users main
>> CROSS JOIN ACL ACL_3
>> JOIN Principals Principals_1 ON ( Principals_1.id = main.id )
>> JOIN CachedGroupMembers CachedGroupMembers_2 ON ( CachedGroupMembers_2.MemberId = Principals_1.id )
>> JOIN CachedGroupMembers CachedGroupMembers_4 ON ( CachedGroupMembers_4.MemberId = Principals_1.id )
>> WHERE
>> (
>> (ACL_3.ObjectType = 'RT::Queue' AND ACL_3.ObjectId = 3) OR
>> (ACL_3.ObjectType = 'RT::System' AND ACL_3.ObjectId = 1)
>> ) AND
>> (ACL_3.PrincipalId = CachedGroupMembers_4.GroupId) AND
>> (ACL_3.PrincipalType = 'Group') AND
>> (ACL_3.RightName = 'OwnTicket') AND
>> (CachedGroupMembers_2.Disabled = '0') AND
>> (CachedGroupMembers_2.GroupId = '4') AND
>> (CachedGroupMembers_4.Disabled = '0') AND
>> (Principals_1.Disabled = '0') AND
>> (Principals_1.PrincipalType = 'User') AND
>> (Principals_1.id != '1')
>> ORDER BY
>> main.Name ASC
>> ;
>>
>> after reverting the LimitToPrivileged out it generates:
>>
>> SELECT
>> DISTINCT main.*
>> FROM
>> Users main
>> CROSS JOIN ACL ACL_2
>> JOIN Principals Principals_1 ON ( Principals_1.id = main.id )
>> JOIN CachedGroupMembers CachedGroupMembers_3 ON ( CachedGroupMembers_3.MemberId = Principals_1.id )
>> WHERE
>> (
>> (ACL_2.ObjectType = 'RT::Queue' AND ACL_2.ObjectId = 3) OR
>> (ACL_2.ObjectType = 'RT::System' AND ACL_2.ObjectId = 1)
>> ) AND
>> (ACL_2.PrincipalId = CachedGroupMembers_3.GroupId) AND
>> (ACL_2.PrincipalType = 'Group') AND
>> (ACL_2.RightName = 'OwnTicket') AND
>> (CachedGroupMembers_3.Disabled = '0') AND
>> (Principals_1.Disabled = '0') AND
>> (Principals_1.PrincipalType = 'User') AND
>> (Principals_1.id != '1')
>> ORDER BY
>> main.Name ASC
>> ;
>>
>> this is the query i came up with:
>>
>> SELECT
>> DISTINCT main.*
>> FROM
>> ACL ACL_3
>> LEFT JOIN Principals ON (ACL_3.principalid = Principals.id)
>> LEFT JOIN cachedgroupmembers ON (Principals.id = cachedgroupmembers.groupid)
>> LEFT JOIN users main ON (cachedgroupmembers.memberid = main.id)
>> JOIN cachedgroupmembers cachedgroupmembers_2 ON (cachedgroupmembers_2.memberid=main.id)
>> WHERE
>> (
>> (ACL_3.ObjectType = 'RT::Queue' AND ACL_3.ObjectId = 3) OR
>> (ACL_3.ObjectType = 'RT::System' AND ACL_3.ObjectId = 1)
>> ) AND
>> (ACL_3.PrincipalType = 'Group') AND
>> (ACL_3.RightName = 'OwnTicket') AND
>> (Principals.disabled = '0') AND
>> (cachedgroupmembers.disabled = '0') AND
>> (cachedgroupmembers_2.groupid = 4) AND
>> (cachedgroupmembers_2.disabled = '0') AND
>> (main.id != 1)
>> ;
>>
>> cheers,
>> dlg
>
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