Re: how to use all the options of EXPLAIN?

When I am using the following query, I got shared hit=8857.

EXPLAIN (buffers true, analyze) select * from act;
QUERY
PLAN
--------------------------------------------------------------------------------------------------------------------------
Seq Scan on act (cost=0.00..6308.82 rows=542312 width=735) (actual
time=0.007..516.199 rows=542312 loops=1)
Buffers: shared hit=8857
Total runtime: 1004.067 ms

Wherears, when I am using the following query, I got Buffers: shared
hit=416 read=46350

EXPLAIN (buffers true, analyze) select * from crm;

QUERY
PLAN
-------------------------------------------------------------------------------------------------------------------------------
Seq Scan on crm (cost=0.00..21558.94 rows=1688234 width=333) (actual
time=0.040..1738.903 rows=1688291 loops=1)
Buffers: shared hit=416 read=46350
Total runtime: 3257.872 ms

Could you please tell me why the different that is why I get read for one
query and not for others?

Thanks.

On Thu, Sep 15, 2011 at 11:59 AM, Toby Corkindale <
toby(dot)corkindale(at)strategicdata(dot)com(dot)au> wrote:

> On 15/09/11 15:43, AI Rumman wrote:
>
>> Could anyone please tell me how to use all the options of explain in
>> Postgresql 9.
>> http://www.postgresql.org/**docs/9.0/static/sql-explain.**html<http://www.postgresql.org/docs/9.0/static/sql-explain.html>
>>
>> I can use EXPLAIN ANALYZE.
>> explain (format yaml) select * from tab1;
>>
>> But
>>
>> explain (format yaml) analyze select * from tab1;
>> ERROR: syntax error at or near "analyze"
>> LINE 1: explain (format yaml) analyze select * from tab1
>>
>>
>> BUFFERS:
>>
>> explain (buffers true) select * from tab1;
>> ERROR: EXPLAIN option BUFFERS requires ANALYZE
>>
>> But
>>
>> explain (buffers true) analyze select * from tab1;
>> ERROR: syntax error at or near "analyze"
>> LINE 1: explain (buffers true) analyze select * from tab1...
>>
>>
>> Same for COSTS.
>>
>> Does any of our experts use these options? If yes, please tell me how.
>>
>
>
> Try putting the ANALYZE inside the parentheses..
> eg
> EXPLAIN (buffers true, analyze) select * from tab1;
>
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