"Hash index" vs. "b-tree index" (PostgreSQL 8.0) - Mailing list pgsql-general

From Ying Lu
Subject "Hash index" vs. "b-tree index" (PostgreSQL 8.0)
Date
Msg-id 427F6853.90308@cs.concordia.ca
Whole thread Raw
Responses Re: "Hash index" vs. "b-tree index" (PostgreSQL 8.0)  (Neil Conway <neilc@samurai.com>)
List pgsql-general
Greetings,

We are working on speeding up the queries by creating indexes. We have
queries with searching criteria such as "select ... where *col1='...'*".
This is a simple query with only "=" operation. As a result I setup hash
index on column "col1". While, in postgreSQL 8 doc, it is wirttern:

*Note: * Testing has shown PostgreSQL's hash indexes to perform no
better than B-tree indexes, and the index size and build time for hash
indexes is much worse. For these reasons, hash index use is presently
discouraged.

May I know for simple "=" operation query, for "Hash index" vs. "B-tree"
index, which can provide better performance please?

Thanks,
Emi

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