[Haskell-cafe] Takusen, postgres and boolean fields
c-bauer-olsbruecken at t-online.de
Sat Apr 25 08:06:08 EDT 2009
Sasha Shipka <xaotuk at gmail.com> writes:
> Let say one has to do something similar to this:
> execDML $ cmdbind (sql "update some_table set some_boolean_field = ?
> where ...") [bindP True, ...]
> When I do it, I have an error:
> DBError ("42","804") 7 "ERROR: 42804: column \"some_boolean_field\"
> is of type boolean but expression is of type text ..."
> I've noticed that when I read boolean fields from postgres it reads
> them as string "t" or "f". So I also tried bindP "t" and had same
Indeed, I also have such problems in my application  in
SELECT boolean_field from TABLE.
My workaround is: I defined a plpgsql function
CREATE OR REPLACE FUNCTION HBoolean(v IN BOOLEAN)
RETURNS TEXT AS $$
IF v THEN RETURN 'True';
ELSE RETURN 'False';
$$ LANGUAGE plpgsql;
and rewrite my query as
SELECT HBoolean(boolean_field) from TABLE
and takusen converts it to Bool.
For performance reason you may convert from text to boolean (but keep
bindP True). If there is a better solution, I'm also glad to know it.
More information about the Haskell-Cafe