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SQL/JSON: support the IS JSON predicate

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This patch introduces the SQL standard IS JSON predicate. It operates
on text and bytea values representing JSON, as well as on the json and
jsonb types. Each test has IS and IS NOT variants and supports a WITH
UNIQUE KEYS flag. The tests are:

IS JSON [VALUE]
IS JSON ARRAY
IS JSON OBJECT
IS JSON SCALAR

These should be self-explanatory.

The WITH UNIQUE KEYS flag makes these return false when duplicate keys
exist in any object within the value, not necessarily directly contained
in the outermost object.

Author: Nikita Glukhov <n.gluhov@postgrespro.ru>
Author: Teodor Sigaev <teodor@sigaev.ru>
Author: Oleg Bartunov <obartunov@gmail.com>
Author: Alexander Korotkov <aekorotkov@gmail.com>
Author: Amit Langote <amitlangote09@gmail.com>
Author: Andrew Dunstan <andrew@dunslane.net>

Reviewers have included (in no particular order) Andres Freund, Alexander
Korotkov, Pavel Stehule, Andrew Alsup, Erik Rijkers, Zihong Yu,
Himanshu Upadhyaya, Daniel Gustafsson, Justin Pryzby.

Discussion: https://postgr.es/m/CAF4Au4w2x-5LTnN_bxky-mq4=WOqsGsxSpENCzHRAzSnEd8+WQ@mail.gmail.com
Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru
Discussion: https://postgr.es/m/20220616233130.rparivafipt6doj3@alap3.anarazel.de
Discussion: https://postgr.es/m/abd9b83b-aa66-f230-3d6d-734817f0995d%40postgresql.org
This commit is contained in:
Alvaro Herrera
2023-03-31 22:34:04 +02:00
parent a2a0c7c29e
commit 6ee30209a6
25 changed files with 1031 additions and 68 deletions
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doc/src/sgml/func.sgml
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@ -16005,6 +16005,86 @@ table2-mapping
</tgroup>
</table>
<para>
<xref linkend="functions-sqljson-misc" /> details SQL/JSON
facilities for testing JSON.
</para>
<table id="functions-sqljson-misc">
<title>SQL/JSON Testing Functions</title>
<tgroup cols="1">
<thead>
<row>
<entry role="func_table_entry"><para role="func_signature">
Function signature
</para>
<para>
Description
</para>
<para>
Example(s)
</para></entry>
</row>
</thead>
<tbody>
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm><primary>IS JSON</primary></indexterm>
<replaceable>expression</replaceable> <literal>IS</literal> <optional> <literal>NOT</literal> </optional> <literal>JSON</literal>
<optional> { <literal>VALUE</literal> | <literal>SCALAR</literal> | <literal>ARRAY</literal> | <literal>OBJECT</literal> } </optional>
<optional> { <literal>WITH</literal> | <literal>WITHOUT</literal> } <literal>UNIQUE</literal> <optional> <literal>KEYS</literal> </optional> </optional>
</para>
<para>
This predicate tests whether <replaceable>expression</replaceable> can be
parsed as JSON, possibly of a specified type.
If <literal>SCALAR</literal> or <literal>ARRAY</literal> or
<literal>OBJECT</literal> is specified, the
test is whether or not the JSON is of that particular type. If
<literal>WITH UNIQUE KEYS</literal> is specified, then any object in the
<replaceable>expression</replaceable> is also tested to see if it
has duplicate keys.
</para>
<para>
<programlisting>
SELECT js,
js IS JSON "json?",
js IS JSON SCALAR "scalar?",
js IS JSON OBJECT "object?",
js IS JSON ARRAY "array?"
FROM (VALUES
('123'), ('"abc"'), ('{"a": "b"}'), ('[1,2]'),('abc')) foo(js);
js | json? | scalar? | object? | array?
------------+-------+---------+---------+--------
123 | t | t | f | f
"abc" | t | t | f | f
{"a": "b"} | t | f | t | f
[1,2] | t | f | f | t
abc | f | f | f | f
</programlisting>
</para>
<para>
<programlisting>
SELECT js,
js IS JSON OBJECT "object?",
js IS JSON ARRAY "array?",
js IS JSON ARRAY WITH UNIQUE KEYS "array w. UK?",
js IS JSON ARRAY WITHOUT UNIQUE KEYS "array w/o UK?"
FROM (VALUES ('[{"a":"1"},
{"b":"2","b":"3"}]')) foo(js);
-[ RECORD 1 ]-+--------------------
js | [{"a":"1"}, +
| {"b":"2","b":"3"}]
object? | f
array? | t
array w. UK? | f
array w/o UK? | t
</programlisting>
</para></entry>
</row>
</tbody>
</tgroup>
</table>
<para>
<xref linkend="functions-json-processing-table"/> shows the functions that
are available for processing <type>json</type> and <type>jsonb</type> values.