Oleg Bartunov <oleg@sai.msu.su> writes: > On Thu, 27 Jan 2005, PFC wrote: > > > > > > > beware that SELECT * FROM table WHERE id =ANY( array ) won't use an > > > > index,
> > > contrib/intarray provides index access to such queries. > > > > Can you provide an example of such a query ? I've looked at the operators > > for intarray without finding it. > > for example, > http://www.sai.msu.su/~megera/postgres/gist/code/7.3/README.intarray > see OPERATIONS and EXAMPLE USAGE: > > SELECT * FROM table WHERE id && int[] I don't think that helps him. He wants the join to the *other* table to use an index. It would be nice if the IN plan used an index for =ANY(array) just like it does for =ANY(subquery) but I'm not sure the statistics are there. It might not be a bad plan to just assume arrays are never going to be millions of elements long though. There is a way to achieve this using "int_array_enum" from another contrib module, "intagg". My current project uses something similar to this except the arrays are precomputed. When I went to 7.4 the new array support obsoleted everything else I was using from the "intagg" and "array" contrib moduels except for this one instance where intagg is still necessary. It is a bit awkward but it works: slo=> EXPLAIN SELECT * FROM foo JOIN (SELECT int_array_enum(foo_ids) AS foo_id FROM cache WHERE cache_id = 1) AS x USING (foo_id) ; QUERY PLAN -------------------------------------------------------------------------------------------------- Nested Loop (cost=0.00..6.40 rows=1 width=726) -> Subquery Scan x (cost=0.00..3.18 rows=1 width=4) -> Index Scan using idx_cache on cache (cost=0.00..3.17 rows=1 width=30) Index Cond: (cache_id = 1) -> Index Scan using foo_pkey on foo (cost=0.00..3.21 rows=1 width=726) Index Cond: (foo.foo_id = "outer".foo_id) (6 rows) (query and plan edited for clarity and for paranoia purposes) -- greg ---------------------------(end of broadcast)--------------------------- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
