Does anybody know how the planner treats casts?
It seems as if casts are not taken into consideration when planning the
query because the costs seem to stay the same.
[hs@backup mag]$ psql -p 5400 test -c "EXPLAIN SELECT id FROM t_data1" QUERY PLAN
-------------------------------------------------------------------Seq Scan on t_data1 (cost=0.00..168966.00
rows=10000000width=4)
(1 row)
[hs@backup mag]$ psql -p 5400 test -c "EXPLAIN SELECT id::numeric FROM
t_data1" QUERY PLAN
-------------------------------------------------------------------Seq Scan on t_data1 (cost=0.00..168966.00
rows=10000000width=4)
(1 row)
[hs@backup mag]$ psql -p 5400 test -c "EXPLAIN SELECT id::text FROM t_data1" QUERY PLAN
-------------------------------------------------------------------Seq Scan on t_data1 (cost=0.00..168966.00
rows=10000000width=4)
(1 row)
[hs@backup mag]$ psql -p 5400 test -c "EXPLAIN SELECT COUNT(id::text)
FROM t_data1" QUERY PLAN
-------------------------------------------------------------------------Aggregate (cost=193966.00..193966.00 rows=1
width=4) -> Seq Scan on t_data1 (cost=0.00..168966.00 rows=10000000 width=4)
(2 rows)
[hs@backup mag]$ psql -p 5400 test -c "EXPLAIN SELECT COUNT(id) FROM
t_data1" QUERY PLAN
-------------------------------------------------------------------------Aggregate (cost=193966.00..193966.00 rows=1
width=4) -> Seq Scan on t_data1 (cost=0.00..168966.00 rows=10000000 width=4)
(2 rows)
Hans
<http://kernel.cybertec.at>
