SELECT l.id, u.id, func(l.id, u.id) FROM ids l CROSS JOIN ids u WHERE l.id < u.id Depending on whether you always update a known pair, or instead invalidate all rows where either id is a given value, you can use various means to manage the resultant materialized view. Triggers or interface functions mainly. Without calling the value function you would also know, at any given time, whether a given pair is present. The usefulness of this depends on how real-time you need the updates to be; which is a trade-off with performance during changes. Adding a simple limit on the two ids sub-queries, and doing the incremental add in a loop, you can appropriately scale the updates to limit memory usage during the bulk load phase. Likely ongoing updates will not have the same requirement since you only have N updates instead of N^2/2; but can be done all the same. SELECT LID, UID, FUNC(lid, uid) FROM SELECT CASE WHEN c1 < c2 THEN c1 ELSE c2 END AS LID , CASE WHEN c1 < c2 THEN c2 ELSE c1 END AS UID FROM SELECT * FROM -> WHERE c1 <> c2 SELECT :newval AS c1, ids.id AS c2 FROM ids David J. -- View this message in context: http://postgresql.1045698.n5.nabble.com/Enforce-Symmetric-Matrix-tp5803064p5803126.html Sent from the PostgreSQL - general mailing list archive at Nabble.com.
