On Aug 29, 2011, at 3:49 PM, Kevin Grittner wrote: > Alexey Klyukin wrote: > >> The following statement produces an error message in PostgreSQL 8.4 >> - 9.2 (head): >> >> postgres=# select val from random()::integer as val; > >> The same statement rewritten with CAST AS works as expected: >> >> postgres=# select val from CAST(random() as integer) as val; > >> The documentation says these casts are equivalent, so either that's >> wrong, or this is a bug. > > Please point out where you think the documentation says that.
Here: > > A type cast specifies a conversion from one data type to another. PostgreSQL > accepts two equivalent syntaxes for type casts: > > CAST ( expression AS type ) > expression::type > http://www.postgresql.org/docs/9.0/interactive/sql-expressions.html#SQL-SYNTAX-TYPE-CASTS > The way I read it, this is the correct syntax: > > test=# select val from (select random()::integer) as x(val); > val > ----- > 1 > (1 row) > > Not only are you missing required parentheses and the SELECT keyword, > you're returning a record rather than a scalar value. SELECT val FROM random() AS val (same as the problematic query, but w/o casts) doesn't produce any errors and IMO is a valid syntax. Here's a quote from the SELECT documentation: > Function calls can appear in the FROM clause. (This is especially useful for > functions that return result sets, but any function can be used.) This acts > as though its output were created as a temporary table for the duration of > this single SELECT command. http://www.postgresql.org/docs/9.0/interactive/sql-select.html The problem is that 2 types of casts behave differently when applied to random() in this query. -- Alexey Klyukin http://www.commandprompt.com The PostgreSQL Company – Command Prompt, Inc. -- Sent via pgsql-bugs mailing list (pgsql-bugs@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-bugs
