Re: [PERFORM] blocking index creation

Try the queries here to check locks:

https://wiki.postgresql.org/wiki/Lock_Monitoring

On Wed, Oct 11, 2017 at 7:35 PM, Neto pr <netopr9@gmail.com> wrote:
> Dear,
> With alternative, I tested the creation using concurrency
> (CREATE INDEX CONCURRENCY NAME_IDX ON TABLE USING HASH (COLUMN);
>
> from what I saw the index already appeared in the query result, because
> before this, the index did not even appear in the result, only the Lineitem
> table:
>
> SELECT
>       L.mode, c.relname, locktype, l.GRANTED, l.transactionid,
> virtualtransaction
> FROM pg_locks l, pg_class c
> where c.oid = l.relation
>
> screen result after concurrency: https://i.stack.imgur.com/htzIY.jpg
>
> Now, I'm waiting to finish creating the index.
>
> 2017-10-11 19:54 GMT-03:00 Neto pr <netopr9@gmail.com>:
>>
>> Hello all,
>> I ran the query on PG_STAT_ACTIVITY table (Select * From
>> pg_stat_activity),  see the complete result in this worksheet of the link
>> below.
>>
>>
>> https://sites.google.com/site/goissbr/img/Resultado_pg_stat_activity-create_index.xls
>>
>> The CREATE INDEX command line is identified with the orange background.
>> At this point 18 hours have passed and the creation of a single index has
>> not yet been completed.
>> I have verified that the command is Active status, but I do not know if
>> it's waiting for anything, can you help me analyze the attached output.
>>
>> Regards
>> Neto
>>
>> 2017-10-11 18:08 GMT-03:00 Tomas Vondra <tomas.vondra@2ndquadrant.com>:
>>>
>>>
>>>
>>> On 10/11/2017 04:11 PM, Neto pr wrote:
>>> >
>>> > 2017-10-11 10:46 GMT-03:00 Laurenz Albe <laurenz.albe@cybertec.at
>>> > <mailto:laurenz.albe@cybertec.at>>:
>>> >
>>> >     Neto pr wrote:
>>> >     > When creating index on table of approximately 10GB of data, the
>>> > DBMS hangs (I think),
>>> >     > because even after waiting 10 hours there was no return of the
>>> > command.
>>> >     > It happened by creating Hash indexes and B + tree indexes.
>>> >     > However, for some columns, it was successfully (L_RETURNFLAG,
>>> > L_PARTKEY).
>>> >
>>> >     > If someone has a hint how to speed up index creation so that it
>>> > completes successfully.
>>> >
>>> >     Look if CREATE INDEX is running or waiting for a lock (check the
>>> >     "pg_locks" table, see if the backend consumes CPU time).
>>> >
>>> >
>>> > In this moment now, there is an index being created in the Lineitem
>>> > table (+ - 10 Gb), and apparently it is locked, since it started 7
>>> > hours
>>> > ago.
>>> > I've looked at the pg_locks table and look at the result, it's with
>>> > "ShareLock" lock mode.
>>> > Is this blocking correct? or should it be another type?
>>> >
>>>
>>> Yes, CREATE INDEX acquire SHARE lock, see
>>>
>>>    https://www.postgresql.org/docs/9.1/static/explicit-locking.html
>>>
>>> > Before creating the index, should I set the type of transaction lock?
>>> > What?
>>>
>>> Eeee? Not sure I understand. The command acquires all necessary locks
>>> automatically.
>>>
>>> >
>>> > -------------------------------------------------------------------------------------------
>>> > SELECT
>>> >       L.mode, c.relname, locktype,  l.GRANTED, l.transactionid,
>>> > virtualtransaction
>>> > FROM   pg_locks l, pg_class   c
>>> > where  c.oid = l.relation
>>> >
>>> > -------------- RESULT
>>> > --------------------------------------------------------------
>>> > AccessShareLock       pg_class_tblspc_relfilenode_index       relation
>>> > TRUE
>>> > (null)        3/71
>>> > AccessShareLock       pg_class_relname_nsp_index      relation
>>> > TRUE    (null)  3/71
>>> > AccessShareLock       pg_class_oid_index      relation        TRUE
>>> > (null)  3/71
>>> > AccessShareLock       pg_class        relation        TRUE    (null)
>>> > 3/71
>>> > AccessShareLock       pg_locks        relation        TRUE    (null)
>>> > 3/71
>>> > ShareLock     lineitem        relation        TRUE    (null)  21/3769
>>> >
>>> >
>>>
>>> Well, we see something is holding a SHARE lock on the "lineitem" table,
>>> but we don't really know what the session is doing.
>>>
>>> There's a PID in the pg_locks table, you can use it to lookup the
>>> session in pg_stat_activity which includes the query (and also "state"
>>> column that will tell you if it's active or waiting for a lock.
>>>
>>> regards
>>>
>>> --
>>> Tomas Vondra                  http://www.2ndQuadrant.com
>>> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>>
>>
>



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To understand recursion, one must first understand recursion.


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