Re: SQL-spec incompatibilities in similar_escape() and related stuff

>>>>> "Andrew" == Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk> writes:

Tom> I am, frankly, inclined to ignore this as a bad idea. We do have
Tom> SIMILAR and ESCAPE as keywords already, but they're
Tom> type_func_name_keyword and unreserved_keyword respectively. To
Tom> support this syntax, I'm pretty sure we'd have to make them both
Tom> fully reserved.

Andrew> I only did a quick trial but it doesn't seem to require
Andrew> reserving them more strictly - just adding the obvious
Andrew> productions to the grammar doesn't introduce any conflicts.

Digging deeper, that's because both SIMILAR and ESCAPE have been
assigned precedence. Ambiguities that exist include:

... COLNAME ! SIMILAR ( ...

which could be COLNAME postfix-op SIMILAR a_expr, or COLNAME infix-op
function-call. Postfix operators strike again... we really should kill
those off.

The ESCAPE part could in theory be ambiguous if the SIMILAR expression
ends in a ... SIMILAR TO xxx operator, since then we wouldn't know
whether to attach the ESCAPE to that or keep it as part of the function
syntax. But I think this is probably a non-issue. More significant is
that ... COLNAME ! ESCAPE ... again has postfix- vs. infix-operator
ambiguities.

--
Andrew (irc:RhodiumToad)