Demitri Muna <postgre...@demitri.com> writes:
> I’m getting stuck on a problem I was hoping I could get some help with. I’m
> trying to create an index for the results of a function that touches two
> tables like this and get the following error:
> CREATE INDEX my_idx ON mytable (first_time(id));
> ERROR: could not read block 0 in file "base/16386/42868": read only 0 of
> 8192 bytes
> CONTEXT: SQL function "first_time" during startup
What's apparently happening is that some query in the function is trying
to examine the newly-created index before it's been populated.
I would call this a bug if it were a supported case, but really you are
doing something you are not allowed to. Functions in indexed expressions
are required to be immutable, and a function that looks at the contents of
a table --- particularly the very table that the index is on --- is simply
not going to be that. Marking such a function immutable to try to end-run
around the restriction is unsafe.
regards, tom lane
