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* Predicate information in EXPLAIN Command
@ 2013-05-14 09:23 Sameer Thakur <samthakur74@gmail.com>
2013-05-14 09:29 ` Re: Predicate information in EXPLAIN Command Heikki Linnakangas <hlinnakangas@vmware.com>
0 siblings, 1 reply; 2+ messages in thread
From: Sameer Thakur @ 2013-05-14 09:23 UTC (permalink / raw)
To: pgsql-performance
Hello,
I am trying to find predicate information for a given SQL query plan as
provided by Oracle using DBMS_XPLAN. I am looking at the EXPLAIN command
for getting this query plan information, with no luck so far.
Does the EXPLAIN command provide predicate information?
Thank you
Sameer
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: Predicate information in EXPLAIN Command
2013-05-14 09:23 Predicate information in EXPLAIN Command Sameer Thakur <samthakur74@gmail.com>
@ 2013-05-14 09:29 ` Heikki Linnakangas <hlinnakangas@vmware.com>
0 siblings, 0 replies; 2+ messages in thread
From: Heikki Linnakangas @ 2013-05-14 09:29 UTC (permalink / raw)
To: Sameer Thakur <samthakur74@gmail.com>; +Cc: pgsql-performance
On 14.05.2013 12:23, Sameer Thakur wrote:
> Hello,
> I am trying to find predicate information for a given SQL query plan as
> provided by Oracle using DBMS_XPLAN. I am looking at the EXPLAIN command
> for getting this query plan information, with no luck so far.
>
> Does the EXPLAIN command provide predicate information?
Sure. For example,
postgres=# explain select * from a where id = 123;
QUERY PLAN
---------------------------------------------------
Seq Scan on a (cost=0.00..40.00 rows=12 width=4)
Filter: (id = 123)
(2 rows)
The predicate is right there on the Filter line. Likewise for a join:
postgres=# explain select * from a, b where a.id = b.id;
QUERY PLAN
-----------------------------------------------------------------
Hash Join (cost=64.00..134.00 rows=2400 width=8)
Hash Cond: (a.id = b.id)
-> Seq Scan on a (cost=0.00..34.00 rows=2400 width=4)
-> Hash (cost=34.00..34.00 rows=2400 width=4)
-> Seq Scan on b (cost=0.00..34.00 rows=2400 width=4)
(5 rows)
The join predicate is on the Hash Cond line.
- Heikki
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2013-05-14 09:23 Predicate information in EXPLAIN Command Sameer Thakur <samthakur74@gmail.com>
2013-05-14 09:29 ` Heikki Linnakangas <hlinnakangas@vmware.com>
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