Rémi Aubel <remi.aubel@gmail.com> writes: > I need to bind a UUID parameter which may be null in a statement like > "select * from test table where ? is null or ? = c_uuid". > Whatever approach I use, the driver rejects my request with "ERROR: could > not determine data type of parameter $1".
Some experimentation suggests that it'd probably work if you wrote the clauses in the other order:
regression=# create table test_table (c_uuid uuid); CREATE TABLE regression=# prepare foo as select * from test_table where $1 is null or $1 = c_uuid; ERROR: could not determine data type of parameter $1 LINE 1: prepare foo as select * from test_table where $1 is null or ... ^ regression=# prepare foo as select * from test_table where $1 = c_uuid or $1 is null; PREPARE
In an ideal world, perhaps the order of the parameter references would not matter, but AFAICS making that work would be mighty hard. For now, PG's parser wants to resolve the type of an otherwise-unlabeled parameter symbol the first time it sees it --- and the context "IS NULL" offers no clue what type it should be.
Alternatively, you could force the issue with an explicit cast in the text of the query:
regression=# prepare foo2 as select * from test_table where $1::uuid is null or $1 = c_uuid; PREPARE
Tom,
This is just a simple example of a bigger problem. One for which there is a solution in the driver which was not implemented.
