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Hash indexes

From: Mladen Gogala <mladen(dot)gogala(at)vmsinfo(dot)com>
To: pgsql-novice(at)postgresql(dot)org
Subject: Hash indexes
Date: 2009-12-15 19:48:18
Message-ID: 1260906498.22825.52.camel@nycwxp2622 (view raw or flat)
Thread:
Lists: pgsql-novice
PostgreSQL has hash indexes, very similar to Oracle bitmap indexes. 
Oracle warns the application designers against using them in the OLTP 
applications because of the locking. Namely, locking a row would lock
all 
the rows which hash to the same hash value as the original row. 
My question is whether the same thing applies to the PostgreSQL hash 
indexes? In the documentation page, I found the following:

http://www.postgresql.org/docs/8.4/interactive/indexes-types.html

CREATE INDEX name ON table USING hash (column);

    Note: Hash index operations are not presently WAL-logged, so hash 
indexes might need to be rebuilt with REINDEX after a database crash.
For 
this reason, hash index use is presently discouraged. 


My question is whether someone here has played with the hash indexes?
Any 
words of caution or blissful experiences? Thanks.


VMS
Mladen Gogala 
Sr. Oracle DBA
1500 Broadway
New York, NY 10036
(212) 329-5251
www.vmsinfo.com 




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