Feedback-ID: ie3de48e3:Fastmail
Date: Fri, 9 May 2025 11:44:24 +0200
From: Alvaro Herrera <alvherre@kurilemu.de>
To: Richard Guo <guofenglinux@gmail.com>
Cc: 
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 <gorbanyoves@basealt.ru>, pgsql-hackers@lists.postgresql.org
Subject: Re: Assert failure in base_yyparse
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On 2025-Apr-14, Richard Guo wrote:

> It seems what happens is that internally in gram.y (~line 14274), the
> DefElem for the not-null option is assigned the name "is_not_null".
> As a result, this allows users to explicitly use "is_not_null" as the
> option name.  However, the value provided for the is_not_null option
> in this way might not be a Boolean as expected, which triggers the
> assertion.
> 
> I kind of doubt we should allow the use of the "is_not_null" keyword
> in the xmltable function.
> 
> Hi Álvaro, what do you think about this?

Hello Richard, sorry that I failed to notice this earlier.

I agree that blocking the index from using the option name that xmltable
parsing uses internally is okay.  Maybe we can rename it to something
like "__pg__is_not_null" or something like that, which would reduce the
chances of troubling people; the existing name sounds too much like a
valid name that users could want to use.

Also, maybe rather than just "syntax error" we could say something like
"option name XYZ cannot be used in XMLTABLE".

I wonder if we have any other names used by the parser that can cause
this kind of problem.  In a quick look through gram.y I didn't find any
other place that would fabricate a name and also accept arbitrary
user-specified names to use, so this seems to be the only place affected
by this particular bug.

-- 
Álvaro Herrera        Breisgau, Deutschland  —  https://www.EnterpriseDB.com/