JSONB operator clarification

In studying our JSONB operators, I was confused about what they do based
on the docs. I found that "contain within" means "contain the
path/value", i.e. it has to match the path from the top level, not just
anywhere inside the document:

SELECT '{"a":1, "c" : {"b":2}}'::jsonb @> '{"a":1}'::jsonb;
?column?
----------
t

SELECT '{"a":1, "c" : {"b":2}}'::jsonb @> '{"b":2}'::jsonb;
?column?
----------
f

You can also specify only the top part of the path:

SELECT '{"a":1, "c" : {"b":2}}'::jsonb @> '{"c":{}}'::jsonb;
?column?
----------
t

SELECT '{"a":1, "c" : {"b":2}}'::jsonb @> '{"d":{}}'::jsonb;
?column?
----------
f

I also found that "key/element string exist" really means "string exist
as a top-level key", e.g.

SELECT '{"a":1, "c" : {"b":2}}'::jsonb ? 'a';
?column?
----------
t

SELECT '{"a":1, "c" : {"b":2}}'::jsonb ? 'b';
?column?
----------
f

The attached doc patch and SQL comment update improves this.

--
Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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