Re: partial index on system indexes?

Bruce Momjian <pgman@candle.pha.pa.us> writes:
> In private email with Tatsuo, I learned it is for the new loadable
> encoding patch, and he wants to use the index from the syscache.  The
> reason for the partial index is because the index itself would not be
> unique, but a partial index would be unique.
> Because the index is part of the syscache, we have to create it as part
> of initdb bootstrap, rather than in the initdb script.

This sounds like a really bad idea to me.  A syscache based on a partial
index is almost certainly not going to work.

Before we invest in a lot of effort making bootstrap, syscache, and who
knows what else support partial indexes, I want to see a very clear
explanation why we must do it.  Note I am looking for "*must* do it",
not "it makes this other part of the system a little simpler".
        regards, tom lane