Hash indexes
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.
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.
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