Martijn van Oosterhout <kleptog@svana.org> writes: > On Wed, Jun 28, 2006 at 03:25:57PM +0300, Tzahi Fadida wrote: >> I need help finding out how to determine if two types are equality compatible >> and compare them.
> Fortunatly the backend contains functions that do all this already. > Check out parser/parse_oper.c, in particular oper() and > compatable_oper(). Note that this still leaves the question of what operator to search for, and where to look for it. The current system doesn't really provide an adequate way of identifying a suitable equality operator; you kind of have to take it on faith that people won't have made "=" do unexpected things (an assumption already violated by some builtin datatypes ...). We've been moving gradually in the direction of relying on btree operator classes to give us a better understanding of which operators really act like equality, but it's far from all done. The most recent thread about fixing this was http://archives.postgresql.org/pgsql-hackers/2006-02/msg00960.php Nothing much has been done since then as far as fixing foreign-key checks, but you might want to look at the code for interpreting row value comparisons (make_row_comparison_op in parse_expr.c). SelectSortFunction in tuplesort.c is another example of looking for btree info to infer the behavior of an operator. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
