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: Alvaro Herrera <alvherre@alvh.no-ip.org>, Andres Freund <andres@anarazel.de>, Andrew Dunstan <andrew@dunslane.net>, Erik Rijkers <er@xs4all.nl>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Tomas Vondra <tomas.vondra@enterprisedb.com>
Date: 2024-03-15T10:30:18Z
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.

On Mon, Mar 11, 2024 at 11:30 AM jian he <jian.universality@gmail.com> wrote:
>
> On Sun, Mar 10, 2024 at 10:57 PM jian he <jian.universality@gmail.com> wrote:
> >
> > one more issue.
>
> Hi
> one more documentation issue.
> after applied V42, 0001 to 0003,
> there are 11 appearance of `FORMAT JSON` in functions-json.html
> still not a single place explained what it is for.
>
> json_query ( context_item, path_expression [ PASSING { value AS
> varname } [, ...]] [ RETURNING data_type [ FORMAT JSON [ ENCODING UTF8
> ] ] ] [ { WITHOUT | WITH { CONDITIONAL | [UNCONDITIONAL] } } [ ARRAY ]
> WRAPPER ] [ { KEEP | OMIT } QUOTES [ ON SCALAR STRING ] ] [ { ERROR |
> NULL | EMPTY { [ ARRAY ] | OBJECT } | DEFAULT expression } ON EMPTY ]
> [ { ERROR | NULL | EMPTY { [ ARRAY ] | OBJECT } | DEFAULT expression }
> ON ERROR ])
>
> FORMAT JSON seems just a syntax sugar or for compatibility in json_query.
> but it returns an error when the returning type category is not
> TYPCATEGORY_STRING.
>
> for example, even the following will return an error.
> `
> CREATE TYPE regtest_comptype AS (b text);
> SELECT JSON_QUERY(jsonb '{"a":{"b":"c"}}', '$.a' RETURNING
> regtest_comptype format json);
> `
>
> seems only types in[0] will not generate an error, when specifying
> FORMAT JSON in JSON_QUERY.
>
> so it actually does something, not a syntax sugar?
>

SELECT * FROM JSON_TABLE(jsonb'[{"aaa": 123}]', 'lax $[*]' COLUMNS
(js2 text format json PATH '$' omit quotes));
SELECT * FROM JSON_TABLE(jsonb'[{"aaa": 123}]', 'lax $[*]' COLUMNS
(js2 text format json PATH '$' keep quotes));
SELECT * FROM JSON_TABLE(jsonb'[{"aaa": 123}]', 'lax $[*]' COLUMNS
(js2 text PATH '$' keep quotes)); -- JSON_QUERY_OP
SELECT * FROM JSON_TABLE(jsonb'[{"aaa": 123}]', 'lax $[*]' COLUMNS
(js2 text PATH '$' omit quotes)); -- JSON_QUERY_OP
SELECT * FROM JSON_TABLE(jsonb'[{"aaa": 123}]', 'lax $[*]' COLUMNS
(js2 text PATH '$')); -- JSON_VALUE_OP
SELECT * FROM JSON_TABLE(jsonb'[{"aaa": 123}]', 'lax $[*]' COLUMNS
(js2 json PATH '$')); -- JSON_QUERY_OP
comparing these queries, I think 'FORMAT JSON' main usage is in json_table.

CREATE TYPE regtest_comptype AS (b text);
SELECT JSON_QUERY(jsonb '{"a":{"b":"c"}}', '$.a' RETURNING
regtest_comptype format json);
ERROR:  cannot use JSON format with non-string output types
LINE 1: ..."a":{"b":"c"}}', '$.a' RETURNING regtest_comptype format jso...
                                                             ^
the error message is not good, but that's a minor issue. we can pursue it later.
-----------------------------------------------------------------------------------------
SELECT JSON_QUERY(jsonb 'true', '$' RETURNING int KEEP QUOTES );
SELECT JSON_QUERY(jsonb 'true', '$' RETURNING int omit QUOTES );
SELECT JSON_VALUE(jsonb 'true', '$' RETURNING int);
the third query returns integer 1, not sure this is the desired behavior.
it obviously has an implication for json_table.
-----------------------------------------------------------------------------------------
in jsonb_get_element, we have something like:
if (jbvp->type == jbvBinary)
{
container = jbvp->val.binary.data;
have_object = JsonContainerIsObject(container);
have_array = JsonContainerIsArray(container);
Assert(!JsonContainerIsScalar(container));
}

+ res = JsonValueListHead(&found);
+ if (res->type == jbvBinary && JsonContainerIsScalar(res->val.binary.data))
+ JsonbExtractScalar(res->val.binary.data, res);
So in JsonPathValue, the above (res->type == jbvBinary) is unreachable?
also see the comment in jbvBinary.

maybe we can just simply do:
if (res->type == jbvBinary)
Assert(!JsonContainerIsScalar(res->val.binary.data));
-----------------------------------------------------------------------------------------
+<synopsis>
+JSON_TABLE (
+  <replaceable>context_item</replaceable>,
<replaceable>path_expression</replaceable> <optional> AS
<replaceable>json_path_name</replaceable> </optional> <optional>
PASSING { <replaceable>value</replaceable> AS
<replaceable>varname</replaceable> } <optional>, ...</optional>
</optional>
+  COLUMNS ( <replaceable
class="parameter">json_table_column</replaceable> <optional>,
...</optional> )
+  <optional> { <literal>ERROR</literal> | <literal>EMPTY</literal> }
<literal>ON ERROR</literal> </optional>
+  <optional>
+    PLAN ( <replaceable class="parameter">json_table_plan</replaceable> ) |
+    PLAN DEFAULT ( { INNER | OUTER } <optional> , { CROSS | UNION } </optional>
+                 | { CROSS | UNION } <optional> , { INNER | OUTER }
</optional> )
+  </optional>
+)

based on the synopsis
the following query should not be allowed?
SELECT *FROM (VALUES ('"11"'), ('"err"')) vals(js)
LEFT OUTER JOIN  JSON_TABLE(vals.js::jsonb, '$' COLUMNS (a int PATH
'$') default '11' ON ERROR) jt ON true;

aslo the synopsis need to reflect case like:
SELECT *FROM (VALUES ('"11"'), ('"err"')) vals(js)
LEFT OUTER JOIN  JSON_TABLE(vals.js::jsonb, '$' COLUMNS (a int PATH
'$') NULL ON ERROR) jt ON true;