unused-targets-20130703.patch

diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index d80c264..7f7b669 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -112,6 +112,7 @@ static void get_column_info_for_window(PlannerInfo *root, WindowClause *wc,
 						   int *ordNumCols,
 						   AttrNumber **ordColIdx,
 						   Oid **ordOperators);
+static List *adjust_targetlist(PlannerInfo *root, List *tlist);
 
 
 /*****************************************************************************
@@ -1016,6 +1017,7 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
 	double		dNumGroups = 0;
 	bool		use_hashed_distinct = false;
 	bool		tested_hashed_distinct = false;
+	bool		tlist_is_adjustable;
 
 	/* Tweak caller-supplied tuple_fraction if have LIMIT/OFFSET */
 	if (parse->limitCount || parse->limitOffset)
@@ -1616,6 +1618,9 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
 		}
 	}							/* end of if (setOperations) */
 
+	/* Check whether we can remove resjunk sort columns safely. */
+	tlist_is_adjustable = is_projection_capable_plan(result_plan);
+
 	/*
 	 * If there is a DISTINCT clause, add the necessary node(s).
 	 */
@@ -1715,6 +1720,9 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
 															   result_plan,
 															current_pathkeys,
 															   -1.0);
+
+				/* We can not remove resjunk sort columns safely. */
+				tlist_is_adjustable = false;
 			}
 
 			result_plan = (Plan *) make_unique(result_plan,
@@ -1738,6 +1746,12 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
 														   limit_tuples);
 			current_pathkeys = root->sort_pathkeys;
 		}
+		else
+		{
+			if (tlist_is_adjustable)
+				result_plan->targetlist =
+					adjust_targetlist(root, result_plan->targetlist);
+		}
 	}
 
 	/*
@@ -3388,6 +3402,141 @@ get_column_info_for_window(PlannerInfo *root, WindowClause *wc, List *tlist,
 	}
 }
 
+/*
+ * adjust_targetlist
+ *		Remove useless resjunk sort columns.
+ *
+ * Note: This function removes top-level resjunk ORDER BY items if the results
+ * are already sorted in the required order by the lower plan node.  This is
+ * useful especially when the ORDER BY expressions are expensive-to-evaluate.
+ * It would be possible to extend to the window ORDER BY case, but we aim at
+ * improving the top-level ORDER BY processing in full-text search.  So, it's
+ * not currently worth complicating the code to make it possible.
+ */
+static List *
+adjust_targetlist(PlannerInfo *root, List *tlist)
+{
+	Query	   *parse = root->parse;
+	Bitmapset  *srefs;
+	Bitmapset  *grefs;
+	ListCell   *lc;
+	bool		found;
+	ListCell   *curr;
+	ListCell   *prev;
+	ListCell   *next;
+
+	/*
+	 * Note that we don't have any resjunk sort columns for SELECT DISTINCT
+	 * (see the comments for transformDistinctClause).
+	 */
+	if (parse->distinctClause && !parse->hasDistinctOn)
+		return tlist;
+
+	/*
+	 * Collect the sortgroupref numbers of ORDER BY clause into a bitmapset
+	 * for convenient reference below.
+	 */
+	srefs = NULL;
+	foreach(lc, parse->sortClause)
+	{
+		SortGroupClause *sortcl = (SortGroupClause *) lfirst(lc);
+
+		srefs = bms_add_member(srefs, sortcl->tleSortGroupRef);
+	}
+
+	/*
+	 * Collect the sortgroupref numbers of GROUP BY, window PARTITION/ORDER BY 
+	 * and DISTINCT ON clauses into a bitmapset for convenient reference below.
+	 */
+	grefs = NULL;
+	if (parse->groupClause)
+	{
+		foreach(lc, parse->groupClause)
+		{
+			SortGroupClause *sortcl = (SortGroupClause *) lfirst(lc);
+
+			grefs = bms_add_member(grefs, sortcl->tleSortGroupRef);
+		}
+	}
+	if (parse->hasWindowFuncs)
+	{
+		foreach(lc, parse->windowClause)
+		{
+			WindowClause *wc = (WindowClause *) lfirst(lc);
+			ListCell   *lc2;
+
+			foreach(lc2, wc->partitionClause)
+			{
+				SortGroupClause *sortcl = (SortGroupClause *) lfirst(lc2);
+
+				grefs = bms_add_member(grefs, sortcl->tleSortGroupRef);
+			}
+			foreach(lc2, wc->orderClause)
+			{
+				SortGroupClause *sortcl = (SortGroupClause *) lfirst(lc2);
+
+				grefs = bms_add_member(grefs, sortcl->tleSortGroupRef);
+			}
+		}
+	}
+	if (parse->hasDistinctOn)
+	{
+		foreach(lc, parse->distinctClause)
+		{
+			SortGroupClause *sortcl = (SortGroupClause *) lfirst(lc);
+
+			grefs = bms_add_member(grefs, sortcl->tleSortGroupRef);
+		}
+	}
+
+	/* Find the sortgroupref numbers used only for ORDER BY clause. */
+	srefs = bms_del_members(srefs, grefs);
+	if (bms_is_empty(srefs))
+		return tlist;
+
+	/* Remove resjunk sort columns, if any. */
+	curr = list_head(tlist);
+	prev = NULL;
+	found = false;
+	while (curr)
+	{
+		TargetEntry *tle = (TargetEntry *) lfirst(curr);
+
+		next = lnext(curr);
+
+		if (tle->resjunk && tle->ressortgroupref != 0 &&
+			bms_is_member(tle->ressortgroupref, srefs))
+		{
+			tlist = list_delete_cell(tlist, curr, prev);
+			found = true;
+		}
+		else
+			prev = curr;
+
+		curr = next;
+	}
+
+	if (found)
+	{
+		int		resno = 1;
+
+		/* Adjust resno in remaining target entries */
+		foreach(lc, tlist)
+		{
+			TargetEntry *tle = (TargetEntry *) lfirst(lc);
+
+			if (tle->resno != resno)
+			{
+				tle = flatCopyTargetEntry(tle);
+				tle->resno = resno;
+			}
+			resno++;
+		}
+	}
+
+	return tlist;
+}
+
 
 /*
  * expression_planner