Re: Nested Loop Left Join always shows rows=1

From: Scara Maccai <m_lists(at)yahoo(dot)it>
To: pgsql-general(at)postgresql(dot)org
Cc: tgl(at)sss(dot)pgh(dot)pa(dot)us
Subject: Re: Nested Loop Left Join always shows rows=1
Date: 2008-12-02 19:49:31
Message-ID: 220177.73018.qm@web28106.mail.ukl.yahoo.com
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> Yeah, this is a bug: it's effectively double-counting the
> selectivity of the index clause. The error isn't enormously critical,
> since the join size estimate is right; but it could perhaps lead to
> choosing a plain indexscan when a bitmap scan would be better. I've
> applied a patch.

Thank you. I'll try that.

I was able to change the PgBackendStatus struct to hold a "percentage of completion" field, which shows up when calling the pg_stat_get_activity function.

As I said in a previous mail, the progress indicator gives very good estimates for the simple queries I need. If I can come up with something that is good in general I'll post it. I'm reading some papers about the argument (mostly the ones listed in http://wiki.postgresql.org/wiki/Query_progress_indication).

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