Re: index not used in ( varchar = text )

"Gaetano Mendola" <mendola(at)bigfoot(dot)com> writes:
>> You need to get rid
>> of the datatype ambiguity. "text = text" is a different operator from
>> "varchar = varchar".

> Yes I agree but was not like this in the Postgres 7.2.X version

That was a bug, or at least a horridly misdesigned behavior. The
operator chosen by the parser is "text = text" (because text is the
preferred datatype in the string class). Leaving aside any issues
about whether the parser's choice is correct, it is surely no business
of the planner to replace that choice with "varchar = varchar" ---
but that's what it was doing. The folly of this idea can be seen by
realizing that the same code would equally happily replace it with
"char = char", which has distinctly different semantics.

regards, tom lane