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Subject: Re: jsonpath: Missing regex_like && starts with Errors?
To: "David E. Wheeler" <david@justatheory.com>,
 PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
References: <9272D3A9-8805-4DE1-A95F-84EB210EC121@justatheory.com>
 <666CFC8E.1000108@acm.org>
From: Chapman Flack <jcflack@acm.org>
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Date: Fri, 14 Jun 2024 23:21:52 -0400
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On 06/14/24 22:29, Chapman Flack wrote:
> So I should go look at our code to see what grammar we've implemented,
> exactly. It is beginning to seem as if we have simply added
> <JSON path predicate> as another choice for an expression, not restricted
> to only appearing in a filter. If so, and we add documentation about how
> we diverge from the standard, that's probably the way to say it.

That's roughly what we've done:


 119 result:
 120     mode expr_or_predicate          {
 121                                         ...
 125                                     }
 126     | /* EMPTY */                   { *result = NULL; }
 127     ;
 128
 129 expr_or_predicate:
 130     expr                            { $$ = $1; }
 131     | predicate                     { $$ = $1; }
 132     ;


Oddly, that's only at the top-level goal production. Your entire JSON
path query we'll allow to be a predicate in lieu of an expr. We still
don't allow a predicate to appear in place of an expr within any other
production.

Regards,
-Chap