Fix regression in subsequent range op. compactions.

We have an anomaly whereby subsequent range operations fail to be
compacted into one single range operation.  This fixes such
behavior.

storage/metric/operation.go

@@ -431,16 +431,12 @@ func optimizeForward(pending ops) (out ops) {
 				continue
 			case *getValuesAlongRangeOp:
 				// Range queries should be concatenated if they overlap.
-				pending = pending[1:len(pending)]
-
 				if next.GreedierThan(t) {
-					t.through = next.through
+					next.from = t.from
 
-					var (
-						head = ops{t}
-					)
-
-					pending = append(head, pending...)
+					return optimizeForward(pending)
+				} else {
+					pending = pending[1:len(pending)]
 				}
 			case *getValuesAtIntervalOp:
 				pending = pending[1:len(pending)]

storage/metric/operation_test.go

@@ -321,6 +321,46 @@ func testOptimizeTimeGroups(t test.Tester) {
 					},
 				},
 			},
+			// Regression Validation 1: Multiple Overlapping Interval Requests
+			//                          This one specific case expects no mutation.
+			{
+				in: ops{
+					&getValuesAlongRangeOp{
+						from:    testInstant,
+						through: testInstant.Add(5 * time.Minute),
+					},
+					&getValuesAlongRangeOp{
+						from:    testInstant.Add(15 * time.Second),
+						through: testInstant.Add(15 * time.Second).Add(5 * time.Minute),
+					},
+					&getValuesAlongRangeOp{
+						from:    testInstant.Add(30 * time.Second),
+						through: testInstant.Add(30 * time.Second).Add(5 * time.Minute),
+					},
+					&getValuesAlongRangeOp{
+						from:    testInstant.Add(45 * time.Second),
+						through: testInstant.Add(45 * time.Second).Add(5 * time.Minute),
+					},
+				},
+				out: ops{
+					&getValuesAlongRangeOp{
+						from:    testInstant,
+						through: testInstant.Add(5 * time.Minute),
+					},
+					&getValuesAlongRangeOp{
+						from:    testInstant.Add(15 * time.Second),
+						through: testInstant.Add(15 * time.Second).Add(5 * time.Minute),
+					},
+					&getValuesAlongRangeOp{
+						from:    testInstant.Add(30 * time.Second),
+						through: testInstant.Add(30 * time.Second).Add(5 * time.Minute),
+					},
+					&getValuesAlongRangeOp{
+						from:    testInstant.Add(45 * time.Second),
+						through: testInstant.Add(45 * time.Second).Add(5 * time.Minute),
+					},
+				},
+			},
 		}
 	)
 
@@ -518,6 +558,34 @@ func testOptimizeForward(t test.Tester) {
 					},
 				},
 			},
+			// Regression Validation 1: Multiple Overlapping Interval Requests
+			//                          We expect to find compaction.
+			{
+				in: ops{
+					&getValuesAlongRangeOp{
+						from:    testInstant,
+						through: testInstant.Add(5 * time.Minute),
+					},
+					&getValuesAlongRangeOp{
+						from:    testInstant.Add(15 * time.Second),
+						through: testInstant.Add(15 * time.Second).Add(5 * time.Minute),
+					},
+					&getValuesAlongRangeOp{
+						from:    testInstant.Add(30 * time.Second),
+						through: testInstant.Add(30 * time.Second).Add(5 * time.Minute),
+					},
+					&getValuesAlongRangeOp{
+						from:    testInstant.Add(45 * time.Second),
+						through: testInstant.Add(45 * time.Second).Add(5 * time.Minute),
+					},
+				},
+				out: ops{
+					&getValuesAlongRangeOp{
+						from:    testInstant,
+						through: testInstant.Add(45 * time.Second).Add(5 * time.Minute),
+					},
+				},
+			},
 		}
 	)
 
@@ -1007,6 +1075,34 @@ func testOptimize(t test.Tester) {
 					},
 				},
 			},
+			// Regression Validation 1: Multiple Overlapping Interval Requests
+			//                          We expect to find compaction.
+			{
+				in: ops{
+					&getValuesAlongRangeOp{
+						from:    testInstant,
+						through: testInstant.Add(5 * time.Minute),
+					},
+					&getValuesAlongRangeOp{
+						from:    testInstant.Add(15 * time.Second),
+						through: testInstant.Add(15 * time.Second).Add(5 * time.Minute),
+					},
+					&getValuesAlongRangeOp{
+						from:    testInstant.Add(30 * time.Second),
+						through: testInstant.Add(30 * time.Second).Add(5 * time.Minute),
+					},
+					&getValuesAlongRangeOp{
+						from:    testInstant.Add(45 * time.Second),
+						through: testInstant.Add(45 * time.Second).Add(5 * time.Minute),
+					},
+				},
+				out: ops{
+					&getValuesAlongRangeOp{
+						from:    testInstant,
+						through: testInstant.Add(45 * time.Second).Add(5 * time.Minute),
+					},
+				},
+			},
 		}
 	)