Re: remaining sql/json patches

Alvaro Herrera <alvherre@alvh.no-ip.org>

From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Amit Langote <amitlangote09@gmail.com>
Cc: Tomas Vondra <tomas.vondra@enterprisedb.com>, Erik Rijkers <er@xs4all.nl>, jian he <jian.universality@gmail.com>, Andres Freund <andres@anarazel.de>, Andrew Dunstan <andrew@dunslane.net>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2024-03-12T20:47:35Z
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.

About 0002:

I think we should just drop it.  Look at the changes it produces in the
plans for aliases XMLTABLE:

> @@ -1556,7 +1556,7 @@ SELECT f.* FROM xmldata, LATERAL xmltable('/ROWS/ROW[COUNTRY_NAME="Japan" or COU
>     Output: f."COUNTRY_NAME", f."REGION_ID"
>     ->  Seq Scan on public.xmldata
>           Output: xmldata.data
> -   ->  Table Function Scan on "xmltable" f
> +   ->  Table Function Scan on "XMLTABLE" f
>           Output: f."COUNTRY_NAME", f."REGION_ID"
>           Table Function Call: XMLTABLE(('/ROWS/ROW[COUNTRY_NAME="Japan" or COUNTRY_NAME="India"]'::text) PASSING (xmldata.data) COLUMNS "COUNTRY_NAME" text, "REGION_ID" integer)
>           Filter: (f."COUNTRY_NAME" = 'Japan'::text)

Here in text-format EXPLAIN, we already have the alias next to the
"xmltable" moniker, when an alias is present.  This matches the
query itself as well as the labels used in the "Output:" display.
If an alias is not present, then this says just 'Table Function Scan on "xmltable"'
and the rest of the plans refers to this as "xmltable", so it's also
fine.

> @@ -1591,7 +1591,7 @@ SELECT f.* FROM xmldata, LATERAL xmltable('/ROWS/ROW[COUNTRY_NAME="Japan" or COU
>             "Parent Relationship": "Inner",                                                                                                                                                      +
>             "Parallel Aware": false,                                                                                                                                                             +
>             "Async Capable": false,                                                                                                                                                              +
> -           "Table Function Name": "xmltable",                                                                                                                                                   +
> +           "Table Function Name": "XMLTABLE",                                                                                                                                                   +
>             "Alias": "f",                                                                                                                                                                        +
>             "Output": ["f.\"COUNTRY_NAME\"", "f.\"REGION_ID\""],                                                                                                                                 +
>             "Table Function Call": "XMLTABLE(('/ROWS/ROW[COUNTRY_NAME=\"Japan\" or COUNTRY_NAME=\"India\"]'::text) PASSING (xmldata.data) COLUMNS \"COUNTRY_NAME\" text, \"REGION_ID\" integer)",+

This is the JSON-format explain.  Notice that the "Alias" member already
shows the alias "f", so the only thing this change is doing is
uppercasing the "xmltable" to "XMLTABLE".  We're not really achieving
anything here.

I think the only salvageable piece from this, **if anything**, is making
the "xmltable" literal string into uppercase.  That might bring a little
clarity to the fact that this is a keyword and not a user-introduced
name.


In your 0003 I think this would only have relevance in this query,

+-- JSON_TABLE() with alias
+EXPLAIN (COSTS OFF, VERBOSE)
+SELECT * FROM
+   JSON_TABLE(
+       jsonb 'null', 'lax $[*]' PASSING 1 + 2 AS a, json '"foo"' AS "b c"
+       COLUMNS (
+           id FOR ORDINALITY,
+           "int" int PATH '$',
+           "text" text PATH '$'
+   )) json_table_func;
+                                                                                                       QUERY PLAN                                             
                                                          
+--------------------------------------------------------------------------------------------------------------------------------------------------------------
----------------------------------------------------------
+ Table Function Scan on "JSON_TABLE" json_table_func
+   Output: id, "int", text
+   Table Function Call: JSON_TABLE('null'::jsonb, '$[*]' AS json_table_path_0 PASSING 3 AS a, '"foo"'::jsonb AS "b c" COLUMNS (id FOR ORDINALITY, "int" integer PATH '$', text text PATH '$') PLAN (json_table_path_0))
+(3 rows)

and I'm curious to see what this would output if this was to be run
without the 0002 patch.  If I understand things correctly, the alias
would be displayed anyway, meaning 0002 doesn't get us anything.

Please do add a test with EXPLAIN (FORMAT JSON) in 0003.

Thanks

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
"La vida es para el que se aventura"