Marti Raudsepp <marti@juffo.org> writes:
> Case #1 uses the normal textcat(text, text) operator by automatically
> coercing 'x' as text.
> However, case #2 uses the anytextcat(anynonarray, text), which is
> marked as volatile thus acts as an optimization barrier.
Hmm ... since those operators were invented (in 8.3), we have adopted a
policy that I/O functions are presumed to be no worse than stable:
http://archives.postgresql.org/pgsql-committers/2010-07/msg00307.php
ISTM that would justify relabeling anytextcat/textanycat as stable,
which should fix this.
> One way would be doing preprocess_expression() before
> pull_up_subqueries() so function inlining happens earlier, but I can't
> imagine what unintended consequences that might have.
I'm pretty sure that would be a bad idea.
regards, tom lane