From d6510791ca3a8796dcba50727d23833015dc865e Mon Sep 17 00:00:00 2001
From: travisturner <travis@umbel.com>
Date: Mon, 15 Sep 2014 14:58:54 -0500
Subject: [PATCH] only run cat step on slices that exist (as opposed to 0-n
 slices)

---
 db/topology.go   | 9 +++++++++
 query/planner.go | 8 +++-----
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/db/topology.go b/db/topology.go
index e5916d5ea..fa5f235ac 100644
--- a/db/topology.go
+++ b/db/topology.go
@@ -183,6 +183,15 @@ func (d *Database) NumSlices() (int, error) {
 	return len(d.slices), nil
 }
 
+// return the slice_ids that are in a database
+func (d *Database) SliceIds() ([]int, error) {
+	var rtn []int
+	for _, slice := range d.slices {
+		rtn = append(rtn, slice.id)
+	}
+	return rtn, nil
+}
+
 ///////// FRAMES ////////////////////////////////////////////////////////////////////
 
 // A frame is a collection of slices in a given category
diff --git a/query/planner.go b/query/planner.go
index 35d7d9674..580af9a8c 100644
--- a/query/planner.go
+++ b/query/planner.go
@@ -459,17 +459,15 @@ func (self *QueryPlanner) buildTree(query *Query, slice int) (QueryTree, error)
 			tree = &CatQueryTree{N: n}
 		}
 		p = tree.(Appendable)
-		numSlices, err := self.Database.NumSlices()
+		slice_ids, err := self.Database.SliceIds()
 		if err != nil {
 			return nil, err
 		}
-		for slice := 0; slice < numSlices; slice++ {
-			//for slice := 0; slice < 3; slice++ {
-			subtree, err := self.buildTree(query, slice)
+		for i := range slice_ids {
+			subtree, err := self.buildTree(query, slice_ids[i])
 			if err != nil {
 				return nil, err
 			}
-
 			p.Append(subtree)
 		}
 	} else {