use levels for cursor.Seek; #34 (#35)

Preetam · Jun 28, 2017 · af44350 · af44350
1 parent 94a55df
commit af44350
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Showing 2 changed files with 22 additions and 14 deletions.
diff --git a/cursor.go b/cursor.go
@@ -143,16 +143,23 @@ func (c *Cursor) Seek(key string) {
 		return
 	}
 
-	var rec *record
 	var err error
-	c.collection.metaLock.RLock()
-	rec, err = c.collection.readRecord(c.collection.Next[0])
-	c.collection.metaLock.RUnlock()
-	if err != nil {
-		if c.current != nil && atomic.LoadInt64(&c.current.Next[0]) != 0 {
+	offset := int64(0)
+	for level := maxLevels - 1; level >= 0; level-- {
+		offset, err = c.collection.findLastLessThanOrEqual(key, offset, level, false)
+		if err != nil {
 			c.err = err
+			return
 		}
-		c.current = nil
+	}
+	if offset == 0 {
+		c.collection.metaLock.RLock()
+		offset = c.collection.Next[0]
+		c.collection.metaLock.RUnlock()
+	}
+	rec, err := c.collection.readRecord(offset)
+	if err != nil {
+		c.err = err
 		return
 	}
 

diff --git a/lm2.go b/lm2.go
@@ -337,10 +337,11 @@ func (c *Collection) writeSentinel() (int64, error) {
 	return offset + 12, nil
 }
 
-func (c *Collection) findLastLessThanOrEqual(key string, startingOffset int64, level int) (int64, error) {
+func (c *Collection) findLastLessThanOrEqual(key string, startingOffset int64, level int, equal bool) (int64, error) {
 	offset := startingOffset
 
-	if c.Next[level] == 0 {
+	headOffset := atomic.LoadInt64(&c.Next[level])
+	if headOffset == 0 {
 		// Empty collection.
 		return 0, nil
 	}
@@ -349,7 +350,7 @@ func (c *Collection) findLastLessThanOrEqual(key string, startingOffset int64, l
 	var err error
 	if offset == 0 {
 		// read the head
-		rec, err = c.readRecord(c.Next[level])
+		rec, err = c.readRecord(headOffset)
 		if err != nil {
 			return 0, err
 		}
@@ -377,7 +378,7 @@ func (c *Collection) findLastLessThanOrEqual(key string, startingOffset int64, l
 
 	for rec != nil {
 		rec.lock.RLock()
-		if rec.Key > key {
+		if (!equal && rec.Key == key) || rec.Key > key {
 			rec.lock.RUnlock()
 			break
 		}
@@ -453,7 +454,7 @@ func (c *Collection) Update(wb *WriteBatch) (int64, error) {
 		}
 
 		for i := maxLevels - 1; i > level; i-- {
-			offset, err := c.findLastLessThanOrEqual(key, startingOffsets[i], i)
+			offset, err := c.findLastLessThanOrEqual(key, startingOffsets[i], i, true)
 			if err != nil {
 				return 0, err
 			}
@@ -466,7 +467,7 @@ func (c *Collection) Update(wb *WriteBatch) (int64, error) {
 		}
 
 		for ; level >= 0; level-- {
-			offset, err := c.findLastLessThanOrEqual(key, startingOffsets[level], level)
+			offset, err := c.findLastLessThanOrEqual(key, startingOffsets[level], level, true)
 			if err != nil {
 				return 0, err
 			}
@@ -545,7 +546,7 @@ func (c *Collection) Update(wb *WriteBatch) (int64, error) {
 	for key := range wb.deletes {
 		offset := int64(0)
 		for level := maxLevels - 1; level >= 0; level-- {
-			offset, err = c.findLastLessThanOrEqual(key, offset, level)
+			offset, err = c.findLastLessThanOrEqual(key, offset, level, true)
 			if err != nil {
 				atomic.StoreUint32(&c.internalState, 1)
 				return 0, err