Re: Documentation on Hash and btree Indexes on jsonb

On Sat, 2021-02-13 at 09:37 +0000, PG Doc comments form wrote:
> The documentation on https://www.postgresql.org/docs/12/datatype-json.html
> claims:
> "jsonb also supports btree and hash indexes. These are usually useful only
> if it's important to check equality of complete JSON documents."
>
> According to some older information from 2016
>
> https://bitnine.net/blog-postgresql/postgresql-internals-jsonb-type-and-its-indexes/?ckattempt=1
> https://stackoverflow.com/questions/36075918/postgresql-index-on-json
> it seems to be a valid option to use hash or btree indexes in that case
> however.
> "As a result, in the choice of an index for JSONB type, if the index
> searches a few predetermined attributes, BTREE is the best choice"
>
> The quoted sentance from the postgres documentation would suggest, that this
> option could be discarded. I would love to hear your feedback on this
> matter.

The PostgreSQL documentation is talking about a B-tree index on the complete
JSON, while the article is talking about a B-tree index on an expression that
extracts one attribute of the JSON.

These are quite different things, so both are correct.

Yours,
Laurenz Albe
--
Cybertec | https://www.cybertec-postgresql.com