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From: Tom Lane <tgl@sss.pgh.pa.us>
To: "David G. Johnston" <david.g.johnston@gmail.com>
cc: Jeff Janes <jeff.janes@gmail.com>,
 Erwin Brandstetter <brsaweda@gmail.com>,
        PostgreSQL Bug List <pgsql-bugs@lists.postgresql.org>
Subject: Re: Variable substitution in jsonb functions fails for jsonpath
 operator like_regex
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Comments: In-reply-to "David G. Johnston" <david.g.johnston@gmail.com>
	message dated "Wed, 18 Oct 2023 19:13:16 -0700"
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"David G. Johnston" <david.g.johnston@gmail.com> writes:
> On Wed, Oct 18, 2023, 18:47 Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Oh, duh, makeItemLikeRegex() is expecting a plain JsonPathString,
>> and JsonPathParseItem.value.like_regex is set up for just a
>> constant pattern.  We could no doubt fix that, but it's a bigger
>> lift than I was hoping.

> Not in a position to do it myself but we should confirm we aren't simply
> following the standard here, and if so decide whether we want to deviate.

Hmm ... looks like we *are* following the standard:


<JSON like_regex predicate> ::=
  <JSON path wff> like_regex <JSON like_regex pattern>
      [ flag <JSON like_regex flags> ]
<JSON like_regex pattern> ::=
  <JSON path string literal>
<JSON like_regex flag> ::=
  <JSON path string literal>

whereas "starts with" has

<JSON starts with predicate> ::=
  <JSON starts with whole> starts with <JSON starts with initial>
<JSON starts with whole> ::=
  <JSON path wff>
<JSON starts with initial> ::=
  <JSON path wff>

The text mentions that "the second operand is permitted to be an SQL/JSON
sequence and to support existential semantics", whereas they evidently
don't want that for a regex pattern.


			regards, tom lane