Stephen Frost <sfr...@snowman.net> writes: > * Tom Lane (t...@sss.pgh.pa.us) wrote: >> Yeah. I'm not very impressed by the underlying assumption that it's >> okay for client-side code to hard-wire knowledge about what indoption >> bits mean, but not okay for it to hard-wire knowledge about which index >> AMs use which indoption bits. There's something fundamentally wrong >> in that. We don't let psql or pg_dump look directly at indoption, so >> why would we think that third-party client-side code should do so?
> For my 2c, I'd like to see pg_dump able to use the catalog tables to > derive the index definition, just as they manage to figure out table > definitions without (for the most part) using functions. More > generally, I believe we should be working to reach a point where we can > reconstruct all objects in the database using just the catalog, without > any SQL bits being provided from special functions which access > information that isn't available at the SQL level. No, I reject that entirely. It would be insane for example to expect that random client-side code should be able to interpret the node trees stored in places like pg_index.indexprs. It's barely possible that we could maintain such logic in pg_dump, though having to maintain a different version for each supported server branch would be a giant PITA. But do you also want to maintain translated-into-Java copies of each of those libraries for the benefit of JDBC? Or any other language that client code might be written in? Now, obviously knowing which bit in pg_index.indoption does what would be a few orders of magnitude less of a maintenance hazard than knowing what expression node trees contain. But that doesn't make it a good future-proof thing for clients to be doing. If the answer to the question "why do you need access to pg_am.amcanorder?" is "so I can interpret the bits in pg_index.indoption", I think it's clear that we've got an abstraction failure that is not going to be fixed by just exposing something equivalent to the old pg_am definition. Building on the has-property approach Andrew suggested, I wonder if we need something like pg_index_column_has_property(indexoid, colno, propertyname) with properties like "sortable", "desc", "nulls first". regards, tom lane -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers