"John L. Clark" <[email protected]> writes:
> I posted this earlier, but I haven't seen it come through the mailing
> list, perhaps because of the attachment. I have also posted the
> attachment at
> <http://infinitesque.net/temp/union_performance_2009-04-21.postgresql.dump.gz>.
Ah. The problem is that your view contains constants in the UNION arms:
CREATE VIEW uri_or_literal_object AS
SELECT literalproperties.subject, literalproperties.subject_term,
literalproperties.predicate, literalproperties.predicate_term,
literalproperties.object, 'L'::character(1) AS object_term,
literalproperties.context, literalproperties.context_term,
literalproperties.data_type, literalproperties.language FROM literalproperties
UNION ALL
SELECT relations.subject, relations.subject_term, relations.predicate,
relations.predicate_term, relations.object, relations.object_term,
relations.context, relations.context_term, NULL::bigint AS data_type,
NULL::character varying(3) AS language FROM relations;
In 8.2 and 8.3, the planner is only smart enough to generate
inner-indexscan nestloop plans on UNIONs if all the elements of the
SELECT lists are simple variables (that is, table columns).
8.4 will be smarter about this.
regards, tom lane
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