Function prepare_query_params

contrib/postgres_fdw/postgres_fdw.c:4850–4890

* Prepare for processing of parameters used in remote query. */

 * Prepare for processing of parameters used in remote query.
 */
static void
prepare_query_params(PlanState *node,
					 List *fdw_exprs,
					 int numParams,
					 FmgrInfo **param_flinfo,
					 List **param_exprs,
					 const char ***param_values)
{
	int			i;
	ListCell   *lc;

	Assert(numParams > 0);

	/* Prepare for output conversion of parameters used in remote query. */
	*param_flinfo = (FmgrInfo *) palloc0(sizeof(FmgrInfo) * numParams);

	i = 0;
	foreach(lc, fdw_exprs)
	{
		Node	   *param_expr = (Node *) lfirst(lc);
		Oid			typefnoid;
		bool		isvarlena;

		getTypeOutputInfo(exprType(param_expr), &typefnoid, &isvarlena);
		fmgr_info(typefnoid, &(*param_flinfo)[i]);
		i++;
	}

	/*
	 * Prepare remote-parameter expressions for evaluation.  (Note: in
	 * practice, we expect that all these expressions will be just Params, so
	 * we could possibly do something more efficient than using the full
	 * expression-eval machinery for this.  But probably there would be little
	 * benefit, and it'd require postgres_fdw to know more than is desirable
	 * about Param evaluation.)
	 */
	*param_exprs = ExecInitExprList(fdw_exprs, node);

	/* Allocate buffer for text form of query parameters. */
	*param_values = (const char **) palloc0(numParams * sizeof(char *));
}

/*
 * Construct array of query parameter values in text format.