Demitri Muna <postgresql@xxxxxxxxxxx> 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
