Re: Issue in _bt_getrootheight

Gurjeet Singh <gurjeet(at)singh(dot)im> writes:
> Please see attached the patch that does this. Let me know if this patch helps.

I don't like this patch one bit, because it adds a lot of overhead
(i.e., an extra index_open/close cycle for every btree index in every
query) to support a tiny minority use-case. How come we don't
already know whether the index is hypothetical at the point where
_bt_getrootheight is called now?

Actually, looking at the existing comment at the call site:

/*
* Allow a plugin to editorialize on the info we obtained from the
* catalogs. Actions might include altering the assumed relation size,
* removing an index, or adding a hypothetical index to the indexlist.
*/
if (get_relation_info_hook)
(*get_relation_info_hook) (root, relationObjectId, inhparent, rel);

reminds me that the design intention was that hypothetical indexes
would get added to the list by get_relation_info_hook itself.
If that's not how the index adviser is operating, maybe we need
to have a discussion about that.

regards, tom lane