Re: FW: KVP table vs. hstore - hstore performance (Was: Postgres NoSQL emulation)

> You wrote
>> Try to create a btree index on "(bench_hstore->bench_id) WHERE
>> (bench_hstore->bench_id) IS NOT NULL".
>
> What do you mean exactly?
> => CREATE INDEX myhstore_kps_gin_idx ON myhstore USING gin(kvps) WHERE
> ??? IS NOT NULL;
>
> My table's def is:
>> CREATE TABLE myhstore ( id bigint PRIMARY KEY, kvps hstore NOT NULL );
> So I'm doing something like:
> CREATE INDEX myhstore_kps_gin_idx ON myhstore USING gin(kvps);

Hello ;

I meant a plain old btree index like this :

CREATE INDEX foo ON myhstore((kvps->'yourkeyname')) WHERE
(kvps->'yourkeyname') IS NOT NULL;

The idea is that :

- The reason to use hstore is to have an arbitrary number of keys and use
the keys you want, not have a fixed set of columns like in a table
- Therefore, no hstore key is present in all rows (if it was, you'd make
it a table column, and maybe index it)
- You'll probably only want to index some of the keys/values (avoiding to
index values that contain serialized data or other stuff that never
appears in a WHERE clause)

So, for each key that corresponds to a searchable attribute, I'd use a
conditional index on that key, which only indexes the relevant rows. For
keys that never appear in a WHERE, no index is needed.

gist is good if you want the intersecton of a hstore with another one (for
instance), btree is good if you want simple search or range search.