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Improve documentation about JSONB array containment behavior.

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Per gripe from Josh Berkus.
This commit is contained in:
Tom Lane 2014-10-11 14:29:51 -04:00
parent 4a50de1312
commit 25ad5a5284
1 changed files with 10 additions and 2 deletions
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12
doc/src/sgml/json.sgml
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@ -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>