Re: Composite fields and the query planner

Steve Rogerson <steve(dot)pg(at)yewtc(dot)demon(dot)co(dot)uk> writes:
> I'm seeing a problem with the query planner not doing what's expected, and I
> think it is because we are using composite fields. Here is a stripped down
> example.

> create type type1 as ( part1 varchar, part2 varchar);
> create table table1 (field1 type1, field2 varchar);
> create function get_part1(type1) returns varchar as $$ select ($1).part1 $$
> language sql;
> create index i1 on table1 (get_part1(field1));
> create index i2 on table1 (field2);

I tested this example in HEAD and 9.0.x and didn't see any particular
problem with rowcount estimates for the get_part1() expression. You
do have to have the i1 index in place when the table is analyzed, else
ANALYZE won't collect any stats about the expression.

regards, tom lane