Postgres 6.3.2 varchar <--> int4 conversions

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I recently had a query fail with the following error:

 keystone=> select members.id, members.element, slips.sid, slips.problem
 keystone->   from slips, members
 keystone->  where members.element = slips.sid
 keystone->    and members.id = 'quickslips';
 ERROR:  There is no operator '=' for types 'varchar' and 'int4'
     You will either have to retype this query using an explicit cast,
     or you will have to define the operator using CREATE OPERATOR

casting the varchar column to int4 works, but if I try to cast the
int4 to varchar I get another error:

 keystone=> select members.id, members.element, slips.sid, slips.problem
 keystone->   from slips, members
 keystone->  where members.element = varchar(slips.sid)
 keystone->    and members.id = 'quickslips';
 ERROR:  parser: parse error at or near "slips"

I would expect that the int4 --> varchar conversion would be the
"safer" one to do.  By "safer" I mean that an int4 value should map to
a distinct varchar value whereas all non-numeric varchar values
generate an error in pg_atoi....

roland
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               PGP Key ID: 66 BC 3B CD
Roland B. Roberts, PhD                  Custom Software Solutions
roberts@panix.com                           101 West 15th St #4NN
rbroberts@acm.org                              New York, NY 10011

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