Initial implementation of Delete on DB.

Signed-off-by: Goutham Veeramachaneni <cs14btech11014@iith.ac.in>

block.go

@@ -222,6 +222,7 @@ func (pb *persistedBlock) Querier(mint, maxt int64) Querier {
 		maxt:       maxt,
 		index:      pb.Index(),
 		chunks:     pb.Chunks(),
+		tombstones: pb.tombstones.Copy(),
 	}
 }
 
@@ -255,10 +256,8 @@ Outer:
 			}
 		}
 
-		// XXX(gouthamve): Adjust mint and maxt to match the time-range in the chunks?
 		for _, chk := range chunks {
-			if (mint <= chk.MinTime && maxt >= chk.MinTime) ||
-				(mint > chk.MinTime && mint <= chk.MaxTime) {
+			if intervalOverlap(mint, maxt, chk.MinTime, chk.MaxTime) {
 				vPostings = append(vPostings, p.At())
 				continue Outer
 			}

compact.go

@@ -307,8 +307,7 @@ func (c *compactor) populate(blocks []Block, indexw IndexWriter, chunkw ChunkWri
 		if len(ranges) > 0 {
 			// Re-encode the chunk to not have deleted values.
 			for _, chk := range chks {
-				// Checks Overlap: http://stackoverflow.com/questions/3269434/
-				if ranges[0].mint <= chk.MaxTime && chk.MinTime <= ranges[len(ranges)-1].maxt {
+				if intervalOverlap(ranges[0].mint, ranges[len(ranges)-1].maxt, chk.MinTime, chk.MaxTime) {
 					newChunk := chunks.NewXORChunk()
 					app, err := newChunk.Appender()
 					if err != nil {

db.go

@@ -669,6 +669,32 @@ func (a *dbAppender) Rollback() error {
 	return g.Wait()
 }
 
+// Delete implements deletion of metrics.
+func (db *DB) Delete(mint, maxt int64, ms ...labels.Matcher) error {
+	s.mtx.RLock()
+
+	s.headmtx.RLock()
+	blocks := s.blocksForInterval(mint, maxt)
+	s.headmtx.RUnlock()
+
+	// TODO(gouthamve): Wait for pending compactions and stop compactions until
+	// delete finishes.
+	var g errgroup.Group
+
+	for _, b := range blocks {
+		f := func() error {
+			return b.Delete(mint, maxt, ms...)
+		}
+		g.Go(f)
+	}
+
+	if err := g.Wait(); err != nil {
+		return err
+	}
+
+	return db.reloadBlocks()
+}
+
 // appendable returns a copy of a slice of HeadBlocks that can still be appended to.
 func (db *DB) appendable() []headBlock {
 	var i int
@@ -681,10 +707,8 @@ func (db *DB) appendable() []headBlock {
 }
 
 func intervalOverlap(amin, amax, bmin, bmax int64) bool {
-	if bmin >= amin && bmin <= amax {
-		return true
-	}
-	if amin >= bmin && amin <= bmax {
+	// Checks Overlap: http://stackoverflow.com/questions/3269434/
+	if amin <= bmax && bmin <= amax {
 		return true
 	}
 	return false