Horton

Re: remaining sql/json patches

jian he <jian.universality@gmail.com>

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From: jian he <jian.universality@gmail.com>
To: Amit Langote <amitlangote09@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Erik Rijkers <er@xs4all.nl>, Andrew Dunstan <andrew@dunslane.net>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2024-01-03T10:53:34Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. SQL/JSON: Various improvements to SQL/JSON query function docs

  2. SQL/JSON: Fix some obsolete comments.

  3. SQL/JSON: Fix issues with DEFAULT .. ON ERROR / EMPTY

  4. JSON_TABLE: Add support for NESTED paths and columns

  5. Fix JsonExpr deparsing to emit QUOTES and WRAPPER correctly

  6. Fix typo introduced in 6185c9737

  7. Add basic JSON_TABLE() functionality

  8. Avoid splitting errmsg string to span multiple lines

  9. Add SQL/JSON query functions

  10. Implement various jsonpath methods

  11. Add soft error handling to some expression nodes

  12. Adjust populate_record_field() to handle errors softly

  13. Refactor code used by jsonpath executor to fetch variables

  14. Test EXPLAIN (FORMAT JSON) ... XMLTABLE

  15. Simplify productions for FORMAT JSON [ ENCODING name ]

  16. Add trailing commas to enum definitions

  17. doc: add missing <returnvalue> and whitespace

  18. Add more SQL/JSON constructor functions

  19. Rename a nonterminal used in SQL/JSON grammar

  20. Some refactoring to export json(b) conversion functions

  21. Don't include CaseTestExpr in JsonValueExpr.formatted_expr

  22. Code review for commit b6e1157e7d

  23. Pass constructName to transformJsonValueExpr()

  24. Unify JSON categorize type API and export for external use

  25. Make some indentation in gram.y consistent

  26. Allow most keywords to be used as column labels without requiring AS.

  27. Reduce size of backend scanner's tables.

  28. Use perfect hashing, instead of binary search, for keyword lookup.

some more minor issues:
SELECT * FROM JSON_TABLE(jsonb '{"a":[123,2]}', '$'
    COLUMNS (item int[] PATH '$.a' error on error, foo text path '$'
error on error)) bar;
ERROR:  JSON path expression in JSON_VALUE should return singleton scalar item

the error message seems not so great, imho.
since the JSON_TABLE doc entries didn't mention that
JSON_TABLE actually transformed to json_value, json_query, json_exists.

JSON_VALUE even though cannot specify KEEP | OMIT QUOTES.
It might be a good idea to mention the default is to omit quotes  in the doc.
because JSON_TABLE actually transformed to json_value, json_query, json_exists.
JSON_TABLE can specify quotes behavior freely.

bother again, i kind of get what the function transformJsonTableChildPlan do,
but adding more comments would make it easier to understand....

(json_query)
+        This function must return a JSON string, so if the path expression
+        returns multiple SQL/JSON items, you must wrap the result using the
+        <literal>WITH WRAPPER</literal> clause. If the wrapper is
+        <literal>UNCONDITIONAL</literal>, an array wrapper will always
+        be applied, even if the returned value is already a single JSON object
+        or an array, but if it is <literal>CONDITIONAL</literal>, it
will not be
+        applied to a single array or object. <literal>UNCONDITIONAL</literal>
+        is the default.  If the result is a scalar string, by default the value
+        returned will have surrounding quotes making it a valid JSON value,
+        which can be made explicit by specifying <literal>KEEP
QUOTES</literal>.
+        Conversely, quotes can be omitted by specifying <literal>OMIT
QUOTES</literal>.
+        The returned <replaceable>data_type</replaceable> has the
same semantics
+        as for constructor functions like <function>json_objectagg</function>;
+        the default returned type is <type>jsonb</type>.

+       <para>
+        Returns the result of applying the
+        <replaceable>path_expression</replaceable> to the
+        <replaceable>context_item</replaceable> using the
+        <literal>PASSING</literal> <replaceable>value</replaceable>s. The
+        extracted value must be a single <acronym>SQL/JSON</acronym> scalar
+        item. For results that are objects or arrays, use the
+        <function>json_query</function> function instead.
+        The returned <replaceable>data_type</replaceable> has the
same semantics
+        as for constructor functions like <function>json_objectagg</function>.
+        The default returned type is <type>text</type>.
+        The <literal>ON ERROR</literal> and <literal>ON EMPTY</literal>
+        clauses have similar semantics as mentioned in the description of
+        <function>json_query</function>.
+       </para>

+        The returned <replaceable>data_type</replaceable> has the
same semantics
+        as for constructor functions like <function>json_objectagg</function>.

IMHO, the above description is not so good, since the function
json_objectagg is listed in functions-aggregate.html,
using Ctrl + F in the browser cannot find json_objectagg in functions-json.html.

for json_query, maybe we can rephrase like:
the RETURNING clause, which specifies the data type returned. It must
be a type for which there is a cast from text to that type.
By default, the <type>jsonb</type> type is returned.

json_value:
the RETURNING clause, which specifies the data type returned. It must
be a type for which there is a cast from text to that type.
By default, the <type>text</type> type is returned.