Function plpgsql_param_eval_generic_ro

src/pl/plpgsql/src/pl_exec.c:6626–6663

* plpgsql_param_eval_generic_ro evaluation of EEOP_PARAM_CALLBACK step * * This handles all variable types, but assumes we need to invoke * MakeExpandedObjectReadOnly (hence, variable must be of a varlena type). */

 * MakeExpandedObjectReadOnly (hence, variable must be of a varlena type).
 */
static void
plpgsql_param_eval_generic_ro(ExprState *state, ExprEvalStep *op,
							  ExprContext *econtext)
{
	ParamListInfo params;
	PLpgSQL_execstate *estate;
	int			dno = op->d.cparam.paramid - 1;
	PLpgSQL_datum *datum;
	Oid			datumtype;
	int32		datumtypmod;

	/* fetch back the hook data */
	params = econtext->ecxt_param_list_info;
	estate = (PLpgSQL_execstate *) params->paramFetchArg;
	Assert(dno >= 0 && dno < estate->ndatums);

	/* now we can access the target datum */
	datum = estate->datums[dno];

	/* fetch datum's value */
	exec_eval_datum(estate, datum,
					&datumtype, &datumtypmod,
					op->resvalue, op->resnull);

	/* safety check -- needed for, eg, record fields */
	if (unlikely(datumtype != op->d.cparam.paramtype))
		ereport(ERROR,
				(errcode(ERRCODE_DATATYPE_MISMATCH),
				 errmsg("type of parameter %d (%s) does not match that when preparing the plan (%s)",
						op->d.cparam.paramid,
						format_type_be(datumtype),
						format_type_be(op->d.cparam.paramtype))));

	/* force the value to read-only */
	*op->resvalue = MakeExpandedObjectReadOnly(*op->resvalue,
											   *op->resnull,
											   -1);
}


/*