Richard Guo <guofenglinux@gmail.com> writes:
> I tested JsonExpr, which is the representation of json_value,
> json_query and json_exists. It seems that they could not produce
> non-NULL output with a NULL input. So we are good on that front.
Seems like we ought to actually look at the relevant code, not
try to test our way to an understanding of it.
I read the ExecInitJsonExpr() code, it has:
/*
* Evaluate formatted_expr storing the result into
* jsestate->formatted_expr.
*/
ExecInitExprRec((Expr *) jsexpr->formatted_expr, state,
&jsestate->formatted_expr.value,
&jsestate->formatted_expr.isnull);
/* JUMP to return NULL if formatted_expr evaluates to NULL */
jumps_return_null = lappend_int(jumps_return_null, state->steps_len);
scratch->opcode = EEOP_JUMP_IF_NULL;
scratch->resnull = &jsestate->formatted_expr.isnull;
scratch->d.jump.jumpdone = -1; /* set below */
ExprEvalPushStep(state, scratch);
The above codes say that it will directly return null if formatted_expr evaluates to NULL.
--
