Date: Sun, 19 Apr 2026 22:21:07 +0200
From: Dmitry Dolgov <9erthalion6@gmail.com>
To: SATYANARAYANA NARLAPURAM <satyanarlapuram@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
	florents.tselai@gmail.com, david@justatheory.com
Subject: Re: BUG: jsonpath .split_part() bypasses lax-mode error suppression
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> On Sat, Apr 18, 2026 at 09:31:03AM -0700, SATYANARAYANA NARLAPURAM wrote:
> Hi hackers,
> 
> The jsonpath string method  .split_part() bypasses lax-mode error
> suppression.
> This is because executeStringInternalMethod() uses
> DirectFunctionCall1(numeric_int4, ...)
> to convert the field number from numeric to int4. This throws
> ereport(ERROR) directly,
> bypassing the jspThrowErrors(cxt) / RETURN_ERROR mechanism that other
> methods
> like .double() use correctly.
> 
> Reproduction:
> -- These should return NULL in lax mode, but throw hard ERRORs:
> SELECT '"hello-world"'::jsonb @? '$.split_part("-", 99999999999)';
> SELECT '"hello-world"'::jsonb @? '$.split_part("-", 0)';
> ERROR:  integer out of range
> ERROR:  field position must not be zero

I don't have a SQL standard at hands, it might be worth checking what SQL/JSON
says about such situations. But at least from the definition of lax mode, given
in the documentation, current behavior seems to be correct:

	lax (default) &mdash; the path engine implicitly adapts the queried data to
	the specified path. Any structural errors that cannot be fixed as described
	below are suppressed, producing no match.

I.e. only structural errors are suppressed, where a structural error defined as:

	An attempt to access a non-existent member of an object or element of an
	array is defined as a structural error.

In this case what we have is an error, which happens due to an incorrect
function argument valye (the second argument of split_part, either out of
integer bound, or zero for 1 based field counting). It has nothing to do with
the jsonb document, and hence doesn't fall into "structural errors" category.