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Re: Row pattern recognition

Henson Choi <assam258@gmail.com>

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From: Henson Choi <assam258@gmail.com>
To: Tatsuo Ishii <ishii@postgresql.org>
Cc: vik@postgresfriends.org, er@xs4all.nl, jacob.champion@enterprisedb.com, david.g.johnston@gmail.com, peter@eisentraut.org, pgsql-hackers@postgresql.org
Date: 2026-02-27T05:44:01Z
Lists: pgsql-hackers 
Hi Tatsuo,

The standard does not allow to use range variables, declared in the
> FROM clause, in the DEFINE clause (19075-5 6.5). Attached patch raises
> an error in this case.
>

Agreed. §6.5 is explicit about mutual exclusivity of the two sets of
range variables. Your patch is correct for this case.

Also, currently we do not support pattern variable range vars in the
> DEFINE caluse (e.g. UP.price). If used, we see a confusing error
> message:
>
> ERROR: missing FROM-clause entry for table "UP"
> LINE 13: UP AS UP.price > PREV(price),
>                ^
>

Pattern variable qualified names like `UP.price` are actually valid
standard syntax (§4.16 uses them in examples), so "is not allowed"
is misleading — "is not supported" would be more accurate.

To distinguish the two cases, we could expose `patternVarNames` via
ParseState (it is already collected by `validateRPRPatternVarCount`
before DEFINE expressions are transformed) and check in
`transformColumnRef` whether the qualifier is a pattern variable:

  - pattern variable qualifier → "not supported"
  - anything else              → "not allowed"

Would it be okay if I revise the patch along those lines?

Best regards,
Henson

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Adjust cross-version upgrade tests for seg_out() fix

  2. Rationalize error comments in partition split/merge tests

  3. Add fast path for foreign key constraint checks

  4. Fix assorted pretty-trivial memory leaks in the backend.

  5. Add temporal FOREIGN KEY contraints

  6. Add trailing commas to enum definitions

  7. Remove obsolete executor cleanup code