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RE: slow join on postgresql6.5

From: "Hiroshi Inoue" <Inoue(at)tpf(dot)co(dot)jp>
To: "Don Baccus" <dhogaza(at)pacifier(dot)com>, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Wenjin Zheng" <wenjin(dot)zheng(at)lsbc(dot)com>, <pgsql-hackers(at)postgresql(dot)org>
Subject: RE: slow join on postgresql6.5
Date: 2000-03-31 10:05:49
Message-ID: 002101bf9af8$b085f840$ (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
> -----Original Message-----
> From: majordomo-owner(at)hub(dot)org [mailto:majordomo-owner(at)hub(dot)org]On Behalf
> Of Don Baccus
> Whatever ... in this particular case  - referential integrity 
> with MATCH <unspecified> and MATCH PARTIAL and multi-column
> foreign keys - performance will likely drop spectacularly once the
> leading column is NULL, while (say) with Oracle you'd expect much
> less of a performance hit. 

As for NULL,it seems possible to look up NULL keys in a btree index
because NULL == NULL for btree indexes.
I've wondered why PostgreSQL's planner/executor never looks up
indexes for queries using 'IS NULL'.


Hiroshi Inoue

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