Re: CREATE INDEX...USING

On Wed, Aug 17, 2022 at 12:41:03PM -0400, Jeff Janes wrote:
> This was recently added to CREATE INDEX reference page:
>
> +        The optional <literal>USING</literal> clause specifies an index
> +        type as described in <xref linkend="indexes-types"/>.  If not
> +        specified, a default index type will be used based on the
> +        data types of the columns.
>
> But I think this is wrong, the default type is BTREE, it does not depend on the
> data type.  Or at least, I've never witnessed the claimed behavior.  The claim
> also conflicts with what is said at https://www.postgresql.org/docs/10/
> indexes-types.html

You are correct --- parser/gram.y has:

        access_method_clause:
                    USING name                              { $$ = $2; }
                    | /*EMPTY*/                             { $$ = DEFAULT_INDEX_TYPE; }

and from include/catalog/index.h:

        #define DEFAULT_INDEX_TYPE  "btree"

Patch attached.