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From Shigeki Kobayashi <shigeki.kobayas...@g.softbank.co.jp>
Subject Re: Too many slow queries caused by MCF running MySQL 5.5
Date Tue, 11 Dec 2012 08:57:39 GMT
Hi Karl.

I could build the source ok but the following code is missing
from connectors.xml. Does this mean I built it incorrectly or this is on
purpose?
Do I have to just add the code to enable the Windows share connection?


  <repositoryconnector name="Windows shares"
class="org.apache.manifoldcf.crawler.connectors.sharedrive.SharedDriveConnector"/>


Regards,

Shigeki


2012/12/11 Karl Wright <daddywri@gmail.com>

> Hi Shigeki,
>
> I'm uploading a new version of ManifoldCF 1.1-dev, which you can pick
> up at http://people.apache.org/~kwright/apache-manifoldcf-1.1-dev .
> This has a good chance of fixing the query performance problem.
> Please try it out, and let me know if you still get slow queries in
> the log.  You should be to use the existing database instance.
>
> Thanks,
> Karl
>
> On Mon, Dec 10, 2012 at 5:05 PM, Karl Wright <daddywri@gmail.com> wrote:
> > Experiments here indicate that FORCE INDEX seems to do what we need.
> >
> > I'm going to think about it a bit and then come up with a fix that
> > should use FORCE INDEX in this situation.  Then we can see if it
> > actually helps for you.
> >
> > Karl
> >
> >
> > On Mon, Dec 10, 2012 at 8:01 AM, Karl Wright <daddywri@gmail.com> wrote:
> >> Sorry, the FORCE INDEX hint requires the name of the index.  Since
> >> ManifoldCF does not assign index names to fixed values, you will need
> >> to find the right one, by using the SHOW INDEX command first to get
> >> the right index's name.
> >>
> >> Apologies,
> >> Karl
> >>
> >>
> >> On Mon, Dec 10, 2012 at 6:41 AM, Karl Wright <daddywri@gmail.com>
> wrote:
> >>> Ok, that is unfortunate.  I will do some further MySQL research here.
> >>> There is a FORCE INDEX MySQL construct that may help, e.g.
> >>>
> >>> SELECT ... FROM ... FORCE INDEX (key1_key2_key3) WHERE ...
> >>>
> >>> which we can also try.  In this case that would be: FORCE INDEX
> >>> (docpriority,status,checkaction,checktime) or FORCE INDEX
> >>> (docpriority_status_checkaction_checktime)  - unclear what the right
> >>> syntax actually is.  Maybe you can try an explain with that in the
> >>> query?
> >>>
> >>> FWIW, PostgreSQL should always use the index for this situation.
> >>>
> >>> Karl
> >>>
> >>>
> >>> On Mon, Dec 10, 2012 at 5:27 AM, Shigeki Kobayashi
> >>> <shigeki.kobayashi3@g.softbank.co.jp> wrote:
> >>>> Hi Karl,
> >>>>
> >>>> Thanks for the reply.
> >>>>
> >>>> I did EXPLAIN as following:
> >>>>
> >>>> mysql> explain SELECT
> >>>>     ->
> >>>> t0.id
> ,t0.jobid,t0.dochash,t0.docid,t0.status,t0.failtime,t0.failcount,t0.priorityset
> >>>>     -> FROM jobqueue t0 WHERE t0.docpriority >= 0 AND t0.status
IN
> ('P','G')
> >>>>     -> AND t0.checkaction='R' AND
> >>>>     -> t0.checktime<=1354605932817 AND EXISTS(SELECT 'x' FROM
jobs t1
> WHERE
> >>>>     -> t1.status IN ('A','a') AND t1.id=t0.jobid AND t1.priority=5)
> AND NOT
> >>>>     -> EXISTS(SELECT 'x' FROM jobqueue t2 WHERE t2.dochash=t0.dochash
> AND
> >>>> t2.status
> >>>>     -> IN ('A','F','a','f','D','d') AND t2.jobid!=t0.jobid) AND NOT
> >>>> EXISTS(SELECT
> >>>>     -> 'x' FROM prereqevents t3,events t4 WHERE t0.id=t3.owner AND
> >>>>     -> t3.eventname=t4.name) ORDER BY t0.docpriority ASC,t0.status
> >>>>     -> ASC,t0.checkaction ASC,t0.checktime ASC LIMIT 1200;
> >>>>
> +----+--------------------+-------+--------+----------------------------------------------+----------------+---------+-------------------------+--------+-----------------------------+
> >>>> | id | select_type        | table | type   | possible_keys
> >>>> | key            | key_len | ref                     | rows   | Extra
> >>>> |
> >>>>
> +----+--------------------+-------+--------+----------------------------------------------+----------------+---------+-------------------------+--------+-----------------------------+
> >>>> |  1 | PRIMARY            | t0    | range  |
> >>>> I1354241297073,I1354241297072,I1354241297071 | I1354241297071 | 25
>    |
> >>>> NULL                    | 151494 | Using where; Using filesort |
> >>>> |  4 | DEPENDENT SUBQUERY | t3    | ref    | I1354241297077
> >>>> | I1354241297077 | 8       | manifoldcf.t0.id        |      1 |
> >>>> |
> >>>> |  4 | DEPENDENT SUBQUERY | t4    | eq_ref | PRIMARY
> >>>> | PRIMARY        | 767     | manifoldcf.t3.eventname |      1 | Using
> index
> >>>> |
> >>>> |  3 | DEPENDENT SUBQUERY | t2    | ref    |
> >>>> I1354241297070,I1354241297073,I1354241297072 | I1354241297070 | 122
>   |
> >>>> manifoldcf.t0.dochash   |      1 | Using where                 |
> >>>> |  2 | DEPENDENT SUBQUERY | t1    | eq_ref | PRIMARY,I1354241297080
> >>>> | PRIMARY        | 8       | manifoldcf.t0.jobid     |      1 | Using
> where
> >>>> |
> >>>>
> +----+--------------------+-------+--------+----------------------------------------------+----------------+---------+-------------------------+--------+-----------------------------+
> >>>>
> >>>>
> >>>> As you see "Using filesort", I do not think it uses the index.
> >>>>
> >>>> By the way, which database do you recommend for the case of crawling
>  a
> >>>> humongous number of files for now? PostgreSQL?
> >>>>
> >>>>
> >>>> Regards,
> >>>>
> >>>> Shigeki
> >>>>
> >>>> 2012/12/10 Karl Wright <daddywri@gmail.com>
> >>>>>
> >>>>> Since you have a large table, can you try an EXPLAIN for the
> following
> >>>>> query, which should match the explanation given here:
> >>>>> http://dev.mysql.com/doc/refman/5.5/en/order-by-optimization.html
?
> >>>>> Does it use the index?
> >>>>>
> >>>>> SELECT
> >>>>>
> >>>>> t0.id
> ,t0.jobid,t0.dochash,t0.docid,t0.status,t0.failtime,t0.failcount,t0.priorityset
> >>>>> FROM jobqueue t0 WHERE t0.docpriority >= 0 AND t0.status IN ('P','G')
> >>>>> AND t0.checkaction='R' AND
> >>>>> t0.checktime<=1354605932817 AND EXISTS(SELECT 'x' FROM jobs t1
WHERE
> >>>>> t1.status IN ('A','a') AND t1.id=t0.jobid AND t1.priority=5) AND
NOT
> >>>>> EXISTS(SELECT 'x' FROM jobqueue t2 WHERE t2.dochash=t0.dochash AND
> >>>>> t2.status
> >>>>> IN ('A','F','a','f','D','d') AND t2.jobid!=t0.jobid) AND NOT
> EXISTS(SELECT
> >>>>> 'x' FROM prereqevents t3,events t4 WHERE t0.id=t3.owner AND
> >>>>> t3.eventname=t4.name) ORDER BY t0.docpriority ASC,t0.status
> >>>>> ASC,t0.checkaction ASC,t0.checktime ASC LIMIT 1200
> >>>>>
> >>>>> Thanks!
> >>>>> Karl
> >>>>>
> >>>>> On Mon, Dec 10, 2012 at 2:49 AM, Karl Wright <daddywri@gmail.com>
> wrote:
> >>>>> > Hi Shigeki,
> >>>>> >
> >>>>> > The rules for when a database will use an index for an ORDER
BY
> clause
> >>>>> > differ significantly from database to database.  The current
logic
> >>>>> > seems to satisfy PostgreSQL, HSQLDB, and Derby, but clearly
not
> MySQL.
> >>>>> >  I will see if I can find a solution.  The ticket for this
> >>>>> > CONNECTORS-584.
> >>>>> >
> >>>>> > Karl
> >>>>> >
> >>>>> > On Mon, Dec 10, 2012 at 2:13 AM, Shigeki Kobayashi
> >>>>> > <shigeki.kobayashi3@g.softbank.co.jp> wrote:
> >>>>> >>
> >>>>> >> Hi.
> >>>>> >>
> >>>>> >>
> >>>>> >> I downloaded MCF1.1dev on Nov, 29th, and ran it using MySQL
> >>>>> >> I tried to crawl 10 million files using Windows share connection
> and
> >>>>> >> index
> >>>>> >> them into Solr.
> >>>>> >>
> >>>>> >> As MCF reached over 1 million files, the crawling speed
started
> getting
> >>>>> >> slower.
> >>>>> >> So I checked slow queries and found out that too many slow
queries
> >>>>> >> occurred,
> >>>>> >> especially the following kinds:
> >>>>> >>
> >>>>> >> --------------------------------------------------------
> >>>>> >> # Time: 121204 16:25:40
> >>>>> >> # User@Host: manifoldcf[manifoldcf] @ localhost [127.0.0.1]
> >>>>> >> # Query_time: 7.240532  Lock_time: 0.000204 Rows_sent:
1200
> >>>>> >> Rows_examined:
> >>>>> >> 611091
> >>>>> >> SET timestamp=1354605940;
> >>>>> >> SELECT
> >>>>> >>
> >>>>> >> t0.id
> ,t0.jobid,t0.dochash,t0.docid,t0.status,t0.failtime,t0.failcount,t0.priorityset
> >>>>> >> FROM jobqueue t0 WHERE t0.status IN ('P','G') AND
> t0.checkaction='R'
> >>>>> >> AND
> >>>>> >> t0.checktime<=1354605932817 AND EXISTS(SELECT 'x' FROM
jobs t1
> WHERE
> >>>>> >> t1.status IN ('A','a') AND t1.id=t0.jobid AND t1.priority=5)
AND
> NOT
> >>>>> >> EXISTS(SELECT 'x' FROM jobqueue t2 WHERE t2.dochash=t0.dochash
AND
> >>>>> >> t2.status
> >>>>> >> IN ('A','F','a','f','D','d') AND t2.jobid!=t0.jobid) AND
NOT
> >>>>> >> EXISTS(SELECT
> >>>>> >> 'x' FROM prereqevents t3,events t4 WHERE t0.id=t3.owner
AND
> >>>>> >> t3.eventname=t4.name) ORDER BY t0.docpriority ASC,t0.status
> >>>>> >> ASC,t0.checkaction ASC,t0.checktime ASC LIMIT 1200;
> >>>>> >> # Time: 121204 16:25:44
> >>>>> >> # User@Host: manifoldcf[manifoldcf] @ localhost [127.0.0.1]
> >>>>> >> # Query_time: 3.064339  Lock_time: 0.000084 Rows_sent:
1
> >>>>> >> Rows_examined:
> >>>>> >> 406359
> >>>>> >> SET timestamp=1354605944;
> >>>>> >> SELECT docpriority,jobid,dochash,docid FROM jobqueue t0
WHERE
> status IN
> >>>>> >> ('P','G') AND checkaction='R' AND checktime<=1354605932817
AND
> >>>>> >> EXISTS(SELECT
> >>>>> >> 'x' FROM jobs t1 WHERE t1.status IN ('A','a') AND t1.id=t0.jobid)
> >>>>> >> ORDER BY
> >>>>> >> docpriority ASC,status ASC,checkaction ASC,checktime ASC
LIMIT 1;
> >>>>> >> -------------------------------------------------------
> >>>>> >>
> >>>>> >> I wonder if the queries appropriately use index of the
table.
> >>>>> >> As a result of EXPLAIN against the slow query, there was
filesort.
> >>>>> >> There seems to be some conditions that MySQL does not use
index
> >>>>> >> depending on
> >>>>> >> ORDER BY:
> >>>>> >>  - Executing ORDER BY against multiple keys
> >>>>> >>  - When keys selected from records are different from keys
used by
> >>>>> >> ORDER BY
> >>>>> >>
> >>>>> >> Since filesort was happening, fully scanning records should
be
> having
> >>>>> >> MCF
> >>>>> >> slower.
> >>>>> >>
> >>>>> >> Do you think this could happen even in PostgreSQL or HSQLDB?
> >>>>> >> Do you think queries could be modified to use index appropriately?
> >>>>> >>
> >>>>> >>
> >>>>> >> Regards,
> >>>>> >>
> >>>>> >> Shigeki
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
>

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