Re: No longer possible to query catalogs for index capabilities?

>>>>> "Tom" == Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:

>> With the gutting of pg_am in 9.6, there seems to be no longer any
>> way for a query of the system catalogs to discover any of the index
>> capabilities that were formerly columns in pg_am (notably
>> amcanorder, amcanorderbyop, amclusterable, amsearcharray,
>> amsearchnulls).

>> Am I missing something or is this a significant oversight?

Tom> It's absolutely not an oversight. We asked when 65c5fcd35 went in
Tom> whether there was still any need for that information to be
Tom> available at the SQL level, and nobody appeared to care.

Perhaps you were asking the wrong people?

Tom> We could in theory expose a view to show the data --- but since a
Tom> large part of the point of that change was to not need initdb for
Tom> AM API changes, and to not be constrained to exactly
Tom> SQL-compatible representations within that API, I'm disinclined to
Tom> do so without a fairly compelling argument why it's needed.

It could easily be exposed as a function interface of the form
index_has_capability(oid,name) or indexam_has_capability(oid,name)
without any initdb worries.

That would surely be better than the present condition of being
completely unable to get this information from SQL.

--
Andrew (irc:RhodiumToad)