Re: rfd: multi-key GiST index problems

> 1. index_getprocid (backend/access/index/idexam.c) doesn't
>    properly supports multi-keys indexes with procnum > 1
>    it's works only if either procnum=1 (B-tree, hash) or attnum=1

It looks to me like IndexSupportInitialize and index_getprocid have
different ideas about whether procnum or attnum is the major index
of the array :-(.  Change one or the other.

>    We didn't find a place where this number is stored in the index structure.

indexRelation->rd_am->amsupport, cf. InitIndexStrategy.

>    In third example with multi-key index we
>    forced to use 'with (islossy)' for all index even if select will
>    use index by first attribute (b gist_box_ops) which is a not right
>    thing.

islossy is a per-index attribute, not a per-column attribute.  I don't
think it makes sense to define it any other way.  If any one of the
columns is stored in a lossy fashion, then the index is lossy.

            regards, tom lane