On 2013-06-18 23:30:44 -0400, Tom Lane wrote: > Andres Freund <and...@2ndquadrant.com> writes: > > On 2013-06-18 13:17:14 +0000, and...@lombardoni.ch wrote: > >> template1=# SELECT CASE WHEN (SELECT 0)=0 THEN 0 ELSE 1/0 END; > >> ERROR: division by zero > > > Hrmpf. This is rather annoying. > > Annoying, maybe. Bug, no. The manual is pretty clear that you don't > have a lot of control over order of evaluation of subexpressions.
For normal clauses I absolutely grant you that. But for CASE? We've always argued that to be escape hatch when you need to force an order. And indeed http://www.postgresql.org/docs/current/static/sql-expressions.html#SYNTAX-EXPRESS-EVAL has the following example: "But this is safe: SELECT ... WHERE CASE WHEN x > 0 THEN y/x > 1.5 ELSE false END;" If the WHEN clause is independent from the arithmetic expression and the vars were replaced by, say query parameters, this will even crash. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-bugs mailing list (pgsql-bugs@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-bugs
