Re: PATCH: default_index_tablespace

jltallon@adv-solutions.net writes:
> This small patch implements a new GUC (default_index_tablespace) plus
> supporting code.
> Originated from a customer request, the feature intends to make
> creation of indexes on SSD-backed tablespaces easy and convenient
> (almost transparent) for users: the DBA can just set it and indexes will
> be placed in the specified tablespace --as opposed to the same
> tablespace where the referenced table is-- without having to specify it
> every time.

I'm afraid this idea is a nonstarter, because it will break existing
applications, and in particular existing pg_dump output files, which
expect to be able to determine an index's tablespace by setting
"default_tablespace".  (It is *not* adequate that the code falls back
to "default_tablespace" if the new GUC is unset; if it is set, you've
still broken pg_dump.)  The incremental value, if indeed there is any,
of being able to control index positioning this way seems unlikely to
justify a backwards-compatibility break of such magnitude.

            regards, tom lane