Re: Pluggable Indexes

Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:

> The original design of Postgres allowed pluggable index access methods,
> but that capability has not been brought forward to allow for WAL. This
> patch would bridge that gap.

Well I think what people do is what GIST did early on -- they just don't
support recoverability until they get merged into core.

Nonetheless this *would* be a worthwhile problem to put effort into solving. I
agree that there are lots of exotic index methods out there that it would be
good to be able to develop externally.

But to do that we need an abstract interface that doesn't depend on internal
data structures, not a generic plugin facility that allows the plugin to
hijack the whole system.

We need something more like indexams which provides a set of call points which
do specific functions, only get called when they're needed, and are expected
to only do the one thing they've been asked to do.

This could be a bit tricky since the catalog isn't available to the wal replay
system. We can't just store the info needed in the pg_indexam table. And it
has to span all the databases in the cluster in any case.

Perhaps this should be solved along with the "plugins" thread. Binary modules
could have some way to register their rmgr id so you could guarantee that
there aren't two plugins with conflicting rmgr ids or version mismatches.

--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
Ask me about EnterpriseDB's Slony Replication support!