Function plpgsql_param_compile

src/pl/plpgsql/src/pl_exec.c:6370–6437

* plpgsql_param_compile paramCompile callback for plpgsql parameters */

 * plpgsql_param_compile		paramCompile callback for plpgsql parameters
 */
static void
plpgsql_param_compile(ParamListInfo params, Param *param,
					  ExprState *state,
					  Datum *resv, bool *resnull)
{
	PLpgSQL_execstate *estate;
	PLpgSQL_expr *expr;
	int			dno;
	PLpgSQL_datum *datum;
	ExprEvalStep scratch;

	/* fetch back the hook data */
	estate = (PLpgSQL_execstate *) params->paramFetchArg;
	expr = (PLpgSQL_expr *) params->parserSetupArg;

	/* paramid's are 1-based, but dnos are 0-based */
	dno = param->paramid - 1;
	Assert(dno >= 0 && dno < estate->ndatums);

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

	scratch.opcode = EEOP_PARAM_CALLBACK;
	scratch.resvalue = resv;
	scratch.resnull = resnull;

	/*
	 * Select appropriate eval function.  It seems worth special-casing
	 * DTYPE_VAR and DTYPE_RECFIELD for performance.  Also, we can determine
	 * in advance whether MakeExpandedObjectReadOnly() will be required.
	 * Currently, only VAR/PROMISE and REC datums could contain read/write
	 * expanded objects.
	 */
	if (datum->dtype == PLPGSQL_DTYPE_VAR)
	{
		if (param != expr->expr_rw_param &&
			((PLpgSQL_var *) datum)->datatype->typlen == -1)
			scratch.d.cparam.paramfunc = plpgsql_param_eval_var_ro;
		else
			scratch.d.cparam.paramfunc = plpgsql_param_eval_var;
	}
	else if (datum->dtype == PLPGSQL_DTYPE_RECFIELD)
		scratch.d.cparam.paramfunc = plpgsql_param_eval_recfield;
	else if (datum->dtype == PLPGSQL_DTYPE_PROMISE)
	{
		if (param != expr->expr_rw_param &&
			((PLpgSQL_var *) datum)->datatype->typlen == -1)
			scratch.d.cparam.paramfunc = plpgsql_param_eval_generic_ro;
		else
			scratch.d.cparam.paramfunc = plpgsql_param_eval_generic;
	}
	else if (datum->dtype == PLPGSQL_DTYPE_REC &&
			 param != expr->expr_rw_param)
		scratch.d.cparam.paramfunc = plpgsql_param_eval_generic_ro;
	else
		scratch.d.cparam.paramfunc = plpgsql_param_eval_generic;

	/*