Horton

Re: remaining sql/json patches

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

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From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Amit Langote <amitlangote09@gmail.com>
Cc: Erik Rijkers <er@xs4all.nl>, jian he <jian.universality@gmail.com>, Andrew Dunstan <andrew@dunslane.net>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2023-09-06T15:01:06Z
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.

0001 is quite mysterious to me.  I've been reading it but I'm not sure I
grok it, so I don't have anything too intelligent to say about it at
this point.  But here are my thoughts anyway.

Assert()ing that a pointer is not null, and in the next line
dereferencing that pointer, is useless: the process would crash anyway
at the time of dereference, so the Assert() adds no value.  Better to
leave the assert out.  (This appears both in ExecExprEnableErrorSafe and
ExecExprDisableErrorSafe).

Is it not a problem to set just the node type, and not reset the
contents of the node to zeroes, in ExecExprEnableErrorSafe?  I'm not
sure if it's possible to enable error-safe on a node two times with an
error reported in between; would that result in the escontext filled
with junk the second time around?  That might be dangerous.  Maybe a
simple cross-check is to verify (assert) in ExecExprEnableErrorSafe()
that the struct is already all-zeroes, so that if this happens, we'll
get reports about it.  (After all, there are very few nodes that handle
the SOFT_ERROR_OCCURRED case).

Do we need to have the ->details_wanted flag turned on?  Maybe if we're
having ExecExprEnableErrorSafe() as a generic tool, it should receive
the boolean to use as an argument.

Why palloc the escontext always, and not just when
ExecExprEnableErrorSafe is called?  (At Disable time, just memset it to
zero, and next time it is enabled for that node, we don't need to
allocate it again, just set the nodetype.)

ExecExprEnableErrorSafe() is a strange name for this operation.  Maybe
you mean ExecExprEnableSoftErrors()?  Maybe it'd be better to leave it
as NULL initially, so that for the majority of cases we don't even
allocate it.

In 0002 you're adding soft-error support for a bunch of existing
operations, in addition to introducing SQL/JSON query functions.  Maybe
the soft-error stuff should be done separately in a preparatory patch.

I think functions such as populate_array_element() that can now save
soft errors and which currently do not have a return value, should
acquire a convention to let caller know that things failed: maybe return
false if SOFT_ERROR_OCCURRED().  Otherwise it appears that, for instance
populate_array_dim_jsonb() can return happily if an error occurs when
parsing the last element in the array.  Splitting 0002 to have a
preparatory patch where all such soft-error-saving changes are
introduced separately would help review that this is indeed being
handled by all their callers.

-- 
Álvaro Herrera        Breisgau, Deutschland  —  https://www.EnterpriseDB.com/
"Por suerte hoy explotó el califont porque si no me habría muerto
 de aburrido"  (Papelucho)