Horton

Re: SQL:2023 JSON simplified accessor support

Chao Li <li.evan.chao@gmail.com>

View thread
From: Chao Li <li.evan.chao@gmail.com>
To: Alexandra Wang <alexandra.wang.oss@gmail.com>
Cc: jian he <jian.universality@gmail.com>, Nikita Malakhov <hukutoc@gmail.com>, Vik Fearing <vik@postgresfriends.org>, Mark Dilger <mark.dilger@enterprisedb.com>, Matheus Alcantara <matheusssilv97@gmail.com>, Peter Eisentraut <peter@eisentraut.org>, Andrew Dunstan <andrew@dunslane.net>, Nikita Glukhov <glukhov.n.a@gmail.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>, "David E. Wheeler" <david@justatheory.com>
Date: 2025-09-10T03:52:05Z
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. Add test coverage for indirection transformation

  2. Fix typo in comment

  3. Implementation of subscripting for jsonb

> <v16-0007-Implement-jsonb-wildcard-member-accessor.patch><v16-0001-Allow-transformation-of-only-a-sublist-of-subscr.patch><v16-0004-Extract-coerce_jsonpath_subscript.patch><v16-0006-Implement-Jsonb-subscripting-with-slicing.patch><v16-0005-Implement-read-only-dot-notation-for-jsonb.patch><v16-0003-Export-jsonPathFromParseResult.patch><v16-0002-Allow-Generic-Type-Subscripting-to-Accept-Dot-No.patch>


A few more comment for v16.

1 - 0002
```
--- a/contrib/hstore/hstore_subs.c
+++ b/contrib/hstore/hstore_subs.c

-	if (isSlice || list_length(*indirection) != 1)
+	if (ai->is_slice || list_length(*indirection) != 1)
```

We should put list_length() check before ai->is_slace. Because when indirection length is greater than 1, it take a single check; other it may need to check the both conditions.

2 - 0002 - also in hstore_subs.c 
```
   *indirection = NIL;
```

We should do “list_delete_first_n(indirection, 1)”.

3 - 0003
```
+Datum
+jsonPathFromParseResult(JsonPathParseResult *jsonpath, int estimated_len,
+						struct Node *escontext)
+{
```

`jsonpath` is not changed in this function, so it should be defined as a const: “const JsonPathParseResult *jsonpath”. 

4 - 0004
```
+		Oid			targets[2] = {INT4OID, TEXTOID};
+
+		/*
+		 * Jsonb can handle multiple subscript types, but cases when a
+		 * subscript could be coerced to multiple target types must be
+		 * avoided, similar to overloaded functions. It could be possibly
+		 * extend with jsonpath in the future.
+		 */
+		for (int i = 0; i < 2; i++)
```

This is a nit optimization. We can do:

Oid targets[] = {INT4OID, TEXTOID};
For (int I = 0; I < sizeof(targets) / sizeof(targets[0]); I ++) 

This way lets the compiler to decide length of “targets”. So that avoids hard code “2” in “for”. If we need to add more elements to “targets”, we can just add it without updating “for”.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/