On Fri, Jun 26, 2015 at 8:05 AM, Robert Haas <robertmh...@gmail.com> wrote:
> I would be fine with adding a *compact* example of this kind to the
> table that begins section 8.14.3. I probably would not back-patch it,
> because the absence of that example is not an error in the
> documentation, but I will not complain if someone else does.
How about the attached? It's a compact refinement of my original
example of more complicated jsonb containment.
I still think it would be a good idea to go back to 9.4. I have reason
to believe that people are getting confused on this point.
--
Peter Geoghegan
diff --git a/doc/src/sgml/json.sgml b/doc/src/sgml/json.sgml
index 118fb35..f5c8fca 100644
--- a/doc/src/sgml/json.sgml
+++ b/doc/src/sgml/json.sgml
@@ -300,11 +300,21 @@ SELECT '{"foo": {"bar": "baz"}}'::jsonb @> '{"foo": {}}'::jsonb;
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.
+ from the containing object. Containment is <emphasis>nested</>.
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.
+ This example shows containment with complex nesting:
</para>
+<programlisting>
+-- By convention, the "doc" jsonb column has an object at the top
+-- level. Each object contains a "tags" array, which itself
+-- contains key/value pairs. Often, "term" tags are available among
+-- tag pairs.
+--
+-- Return "site_name" where at least these two terms appear:
+SELECT doc->'site_name' from websites where doc @> '{"tags":[{"term":"paris" }, {"term":"food"}]}';
+</programlisting>
<para>
As a special exception to the general principle that the structures
--
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