Re: remaining sql/json patches

On Mon, Oct 16, 2023 at 5:47 PM Amit Langote <amitlangote09(at)gmail(dot)com> wrote:
>
> > We're currently looking into this case.
>
> Thanks for the report. I think I've figured out the problem --
> ExecEvalJsonExprCoercion() mishandles the EMPTY ARRAY ON EMPTY case.
>
> I'm reading the other 2 patches...
>
> --
> Thanks, Amit Langote
> EDB: http://www.enterprisedb.com

query: select JSON_QUERY('[]'::jsonb, '$.mm' RETURNING text OMIT
QUOTES EMPTY ON EMPTY);

Breakpoint 2, ExecEvalJsonExpr (state=0x55e47ad685c0,
op=0x55e47ad68818, econtext=0x55e47ad682e8) at
../../Desktop/pg_sources/main/postgres/src/backend/executor/execExprInterp.c:4188
4188 JsonExprState *jsestate = op->d.jsonexpr.jsestate;
(gdb) fin
Run till exit from #0 ExecEvalJsonExpr (state=0x55e47ad685c0,
op=0x55e47ad68818, econtext=0x55e47ad682e8)
at ../../Desktop/pg_sources/main/postgres/src/backend/executor/execExprInterp.c:4188
ExecInterpExpr (state=0x55e47ad685c0, econtext=0x55e47ad682e8,
isnull=0x7ffe63659e2f) at
../../Desktop/pg_sources/main/postgres/src/backend/executor/execExprInterp.c:1556
1556 EEO_NEXT();
(gdb) p *op->resnull
$1 = true
(gdb) cont
Continuing.

Breakpoint 1, ExecEvalJsonExprCoercion (state=0x55e47ad685c0,
op=0x55e47ad68998, econtext=0x55e47ad682e8, res=94439801785192,
resnull=false) at
../../Desktop/pg_sources/main/postgres/src/backend/executor/execExprInterp.c:4453
4453 {
(gdb) i args
state = 0x55e47ad685c0
op = 0x55e47ad68998
econtext = 0x55e47ad682e8
res = 94439801785192
resnull = false
(gdb) p *op->resnull
$2 = false
-------------------------------------------------------
in ExecEvalJsonExpr, *op->resnull is true.
then in ExecEvalJsonExprCoercion *op->resnull is false.
I am not sure why *op->resnull value changes, when changes.
-------------------------------------------------------
in ExecEvalJsonExprCoercion, if resnull is true, then jb is null, but
it seems there is no code to handle the case.
-----------------------------
add the following code after ExecEvalJsonExprCoercion if
(!InputFunctionCallSafe(...) works, but seems like a hack.

if (!val_string)
{
*op->resnull = true;
*op->resvalue = (Datum) 0;
}