Re: Postgres not using GiST index in a lateral join

I got the query plan using:
EXECUTE EXPLAIN (format json) ... INTO query_plan;
RAISE NOTICE query_plan;

since by default EXPLAIN returns a set of rows and I'd have to create a
table for storing that. As I mentioned in the original email,
the queries and output is nicely formatted at:

http://stackoverflow.com/questions/28856452/postgres-not-using-gist-index-in-lateral-join

On Thu, Mar 5, 2015 at 11:54 AM Alban Hertroys <haramrae(at)gmail(dot)com> wrote:

>
> > On 04 Mar 2015, at 22:18, Igor Stassiy <istassiy(at)gmail(dot)com> wrote:
> >
> > I would like to stop executing the query for a row of table "a" when a
> single row of "b" is found. This query would not stop
> > processing but will filter all the rows that are found at the end of
> execution.
> >
> > Is there a way to express this without a subquery?
>
> Does it? Because that would be somewhat surprising.
>
> > On Wed, Mar 4, 2015 at 11:53 PM Paul Ramsey <pramsey(at)cleverelephant(dot)ca>
> wrote:
> > Stop writing so many subqueries, think in joins; the poor planner!
> >
> > SELECT DISTINCT ON (a.id) a.id AS a_id, b.id AS b_id
> > FROM a
> > JOIN b
> > ON ST_Contains(b.shape, a.shape)
> > WHERE b.kind != 1
> >
> > Also, the DISTINCT ON syntax (PgSQL custom) lets you winnow a result
> > set down to just one of the inputs.
>
>
> > > -- for each row in A, select exactly one row in B (if there is one)
> > > -- such that B contains geometry of A
> > > EXPLAIN SELECT * FROM (SELECT A.id as aid, (SELECT B.id FROM B WHERE
> > > ST_Contains(B.shape, A.shape) AND B.kind != 1 LIMIT 1) as bid FROM A)
> AS
> > > TMP;
> > >
> > > which gives me { "Plan": { "Node Type": "Seq Scan", "Relation Name":
> "A",
> > > "Startup Cost": 0.00, "Total Cost": 2606592.33, "Plan Rows": 549745,
> "Plan
> > > Width": 1646, "Plans": [ { "Node Type": "Limit", "Parent Relationship":
> > > "SubPlan", "Subplan Name": "SubPlan 1", "Startup Cost": 0.00, "Total
> Cost":
> > > 4.68, "Plan Rows": 1, "Plan Width": 8, "Plans": [ { "Node Type": "Seq
> Scan",
> > > "Parent Relationship": "Outer", "Relation Name": "B", "Startup Cost":
> 0.00,
> > > "Total Cost": 4.68, "Plan Rows": 1, "Plan Width": 8, "Filter":
> "((shape &&
> > > A.shape) AND _st_contains(shape, A.shape))" } ] } ] } }
>
> How did your query plan end up in JSON notation? It's quite difficult to
> read like this.
>
> Alban Hertroys
> --
> If you can't see the forest for the trees,
> cut the trees and you'll find there is no forest.
>
>