Re: SQL/JSON features for v15

Amit Langote <amitlangote09@gmail.com>

From: Amit Langote <amitlangote09@gmail.com>

To: Nikita Glukhov <n.gluhov@postgrespro.ru>

Cc: "Jonathan S. Katz" <jkatz@postgresql.org>, Andres Freund <andres@anarazel.de>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Andrew Dunstan <andrew@dunslane.net>, Tom Lane <tgl@sss.pgh.pa.us>, Michael Paquier <michael@paquier.xyz>, John Naylor <john.naylor@enterprisedb.com>

Date: 2022-08-23T08:21:59Z

Lists: pgsql-hackers

On Tue, Aug 23, 2022 at 4:48 PM Amit Langote <amitlangote09@gmail.com> wrote:
> On Thu, Aug 18, 2022 at 12:46 PM Nikita Glukhov <n.gluhov@postgrespro.ru> wrote:
> > The desciprion of the v7 patches:
> >
> > 0003 Add EEOP_SUBTRANS executor step
> >   v6 + new recursive JIT
> >
> > 0004 Split JsonExpr execution into steps
> >   simply rebase of v6 + used LLMBuildSwitch() in EEOP_JSONEXPR
>
> Will need to spend more time looking at these.

0004 adds the following to initJsonItemCoercions():

+   /* When returning JSON types, no need to initialize coercions */
+   /* XXX domain types on json/jsonb */
+   if (returning->typid == JSONBOID || returning->typid == JSONOID)
+       return NULL;

But maybe it's dead code, because 0001 has this:

+           if (jsexpr->returning->typid != JSONOID &&
+               jsexpr->returning->typid != JSONBOID)
+               jsexpr->coercions =
+                   initJsonItemCoercions(pstate, jsexpr->returning,
+                                         exprType(contextItemExpr));

+               /* We need to handle RETURNING int etc. */

Is this a TODO and what does it mean?

+ *     "JsonCoercion == NULL" means no cast is available.
+ *         "JsonCoercion.expr == NULL" means no coercion is needed.

As said in my previous email, I wonder if these cases are better
handled by adding JSON_COERCION_ERROR and JSON_COERCION_NONE
coercions?

+/* Skip calling ExecEvalJson() on a JsonExpr? */

ExecEvalJsonExpr()

Will look more.

-- 
Thanks, Amit Langote
EDB: http://www.enterprisedb.com

Commits

JSON_TABLE: Add support for NESTED paths and columns
- bb766cde63b4 17.0 landed
Add basic JSON_TABLE() functionality
- de3600452b61 17.0 landed
Add SQL/JSON query functions
- 6185c9737cf4 17.0 landed
Add soft error handling to some expression nodes
- aaaf9449ec6b 17.0 landed
Adjust populate_record_field() to handle errors softly
- 1edb3b491bee 17.0 landed
Refactor code used by jsonpath executor to fetch variables
- faa2b953ba3b 17.0 landed
Add more SQL/JSON constructor functions
- 03734a7fed7d 17.0 landed
SQL/JSON: support the IS JSON predicate
- 6ee30209a6f1 16.0 landed
SQL/JSON: add standard JSON constructor functions
- 7081ac46ace8 16.0 landed
Revert SQL/JSON features
- 96ef3237bf74 15.0 landed
- 2f2b18bd3f55 16.0 landed
Numeric error suppression in jsonpath
- 16d489b0fe05 12.0 cited