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Re: how to get the total number of records in report

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Merlin Moncure <mmoncure(at)gmail(dot)com>
Cc: AI Rumman <rummandba(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: how to get the total number of records in report
Date: 2010-10-28 17:05:30
Message-ID: AANLkTi=M=ehvBJMbiu1-iiC48QmUfs_bcMBStz4mJBB6@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Tue, Oct 19, 2010 at 7:56 PM, Merlin Moncure <mmoncure(at)gmail(dot)com> wrote:
> On Mon, Oct 18, 2010 at 1:16 AM, AI Rumman <rummandba(at)gmail(dot)com> wrote:
>> At present for reporting I use following types of query:
>> select crm.*, crm_cnt.cnt
>> from crm,
>> (select count(*) as cnt from crm) crm_cnt;
>> Here count query is used to find the total number of records.
>> Same FROM clause is copied in both the part of the query.
>> Is there any other good alternative way to get this similar value?
>
> Probably the best way to do this type of thing is handle it on the
> client.  However, if you want to do it this way and your from clause
> is more complex than 'from table', you can possibly improve on this
> with a CTE:
>
> with q as (select * from <something expensive>)
> select q.* q_cnt.cnt from q, (select count(*) as cnt from q) q_cnt;
>
> The advantage here is that the CTE is materialized without having to
> do the whole query again.  This can be win or loss depending on the
> query.

What about

select crm.*, sum(1) over () as crm_count from crm limit 10;

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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