Function transformScatterClause

src/backend/parser/parse_clause.c:3311–3345

* transformScatterClause - * transform a SCATTER BY clause * * SCATTER BY items will be added to the targetlist (as resjunk columns) * if not already present, so the targetlist must be passed by reference. * */

 *
 */
List *
transformScatterClause(ParseState *pstate,
					   List *scatterlist,
					   List **targetlist)
{
	List	   *outlist = NIL;
	ListCell   *olitem;

	/* Special case handling for SCATTER RANDOMLY */
	if (list_length(scatterlist) == 1 && linitial(scatterlist) == NULL)
		return list_make1(NULL);
	
	/* preprocess the scatter clause, lookup TLEs */
	foreach(olitem, scatterlist)
	{
		Node			*node = lfirst(olitem);
		TargetEntry		*tle;

		tle = findTargetlistEntrySQL99(pstate, node, targetlist,
									   EXPR_KIND_SCATTER_BY);

		/* coerce unknown to text */
		if (exprType((Node *) tle->expr) == UNKNOWNOID)
		{
			tle->expr = (Expr *) coerce_type(pstate, (Node *) tle->expr,
											 UNKNOWNOID, TEXTOID, -1,
											 COERCION_IMPLICIT,
											 COERCE_IMPLICIT_CAST,
											 -1);
		}

		outlist = lappend(outlist, tle->expr);
	}
	return outlist;
}

/*
 * get_matching_location