From 308ab77b89ec1662f24b5ab4013ff0d1bd4153a1 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Sat, 11 Oct 2014 14:29:51 -0400 Subject: [PATCH] Improve documentation about JSONB array containment behavior. Per gripe from Josh Berkus. --- doc/src/sgml/json.sgml | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/doc/src/sgml/json.sgml b/doc/src/sgml/json.sgml index 37dd611aeb..8feb2fbf0a 100644 --- a/doc/src/sgml/json.sgml +++ b/doc/src/sgml/json.sgml @@ -269,6 +269,12 @@ SELECT '"foo"'::jsonb @> '"foo"'::jsonb; -- The array on the right side is contained within the one on the left: SELECT '[1, 2, 3]'::jsonb @> '[1, 3]'::jsonb; +-- Order of array elements is not significant, so this is also true: +SELECT '[1, 2, 3]'::jsonb @> '[3, 1]'::jsonb; + +-- Duplicate array elements don't matter either: +SELECT '[1, 2, 3]'::jsonb @> '[1, 2, 2]'::jsonb; + -- The object with a single pair on the right side is contained -- within the object on the left side: SELECT '{"product": "PostgreSQL", "version": 9.4, "jsonb":true}'::jsonb @> '{"version":9.4}'::jsonb; @@ -288,8 +294,10 @@ SELECT '{"foo": {"bar": "baz"}}'::jsonb @> '{"bar": "baz"}'::jsonb; -- yields f The general principle is that the contained object must match the containing object as to structure and data contents, possibly after discarding some non-matching array elements or object key/value pairs - from the containing object. However, the order of array elements is - not significant when doing a containment match. + from the containing object. + But remember that the order of array elements is not significant when + doing a containment match, and duplicate array elements are effectively + considered only once.