From 25ad5a52847699527ddba6e86aa353075e578e9b Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
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 37dd611aeb7..8feb2fbf0ad 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.
</para>
<para>
--
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