Performance Improvements to block iterator (hypermodeinc#977)

Signed-off-by: thomassong <[email protected]>

table/iterator.go

@@ -40,14 +40,15 @@ type blockIterator struct {
 	last header // The last header we saw.
 }
 
-func (itr *blockIterator) Reset() {
+func (itr *blockIterator) setBlock(b *block) {
 	itr.pos = 0
 	itr.err = nil
-	itr.baseKey = []byte{}
-	itr.key = []byte{}
-	itr.val = []byte{}
+	itr.baseKey = itr.baseKey[:0]
+	itr.key = itr.key[:0]
+	itr.val = itr.val[:0]
 	itr.init = false
 	itr.last = header{}
+	itr.data = b.data
 }
 
 func (itr *blockIterator) Init() {
@@ -77,7 +78,7 @@ func (itr *blockIterator) Seek(key []byte, whence int) {
 
 	switch whence {
 	case origin:
-		itr.Reset()
+		// We don't need to do anything. startIndex is already at 0
 	case current:
 	}
 
@@ -195,7 +196,7 @@ func (itr *blockIterator) Value() []byte {
 type Iterator struct {
 	t    *Table
 	bpos int
-	bi   *blockIterator
+	bi   blockIterator
 	err  error
 
 	// Internally, Iterator is bidirectional. However, we only expose the
@@ -238,7 +239,7 @@ func (itr *Iterator) seekToFirst() {
 		itr.err = err
 		return
 	}
-	itr.bi = block.NewIterator()
+	itr.bi.setBlock(block)
 	itr.bi.SeekToFirst()
 	itr.err = itr.bi.Error()
 }
@@ -255,7 +256,7 @@ func (itr *Iterator) seekToLast() {
 		itr.err = err
 		return
 	}
-	itr.bi = block.NewIterator()
+	itr.bi.setBlock(block)
 	itr.bi.SeekToLast()
 	itr.err = itr.bi.Error()
 }
@@ -267,7 +268,7 @@ func (itr *Iterator) seekHelper(blockIdx int, key []byte) {
 		itr.err = err
 		return
 	}
-	itr.bi = block.NewIterator()
+	itr.bi.setBlock(block)
 	itr.bi.Seek(key, origin)
 	itr.err = itr.bi.Error()
 }
@@ -334,13 +335,13 @@ func (itr *Iterator) next() {
 		return
 	}
 
-	if itr.bi == nil {
+	if len(itr.bi.data) == 0 {
 		block, err := itr.t.block(itr.bpos)
 		if err != nil {
 			itr.err = err
 			return
 		}
-		itr.bi = block.NewIterator()
+		itr.bi.setBlock(block)
 		itr.bi.SeekToFirst()
 		itr.err = itr.bi.Error()
 		return
@@ -349,7 +350,7 @@ func (itr *Iterator) next() {
 	itr.bi.Next()
 	if !itr.bi.Valid() {
 		itr.bpos++
-		itr.bi = nil
+		itr.bi.data = nil
 		itr.next()
 		return
 	}
@@ -362,13 +363,13 @@ func (itr *Iterator) prev() {
 		return
 	}
 
-	if itr.bi == nil {
+	if len(itr.bi.data) == 0 {
 		block, err := itr.t.block(itr.bpos)
 		if err != nil {
 			itr.err = err
 			return
 		}
-		itr.bi = block.NewIterator()
+		itr.bi.setBlock(block)
 		itr.bi.SeekToLast()
 		itr.err = itr.bi.Error()
 		return
@@ -377,7 +378,7 @@ func (itr *Iterator) prev() {
 	itr.bi.Prev()
 	if !itr.bi.Valid() {
 		itr.bpos--
-		itr.bi = nil
+		itr.bi.data = nil
 		itr.prev()
 		return
 	}

table/table.go

@@ -31,9 +31,10 @@ import (
 	"sync/atomic"
 
 	"github.com/AndreasBriese/bbloom"
+	"github.com/pkg/errors"
+
 	"github.com/dgraph-io/badger/options"
 	"github.com/dgraph-io/badger/y"
-	"github.com/pkg/errors"
 )
 
 const fileSuffix = ".sst"
@@ -283,14 +284,14 @@ func (t *Table) readIndex() error {
 	return nil
 }
 
-func (t *Table) block(idx int) (block, error) {
+func (t *Table) block(idx int) (*block, error) {
 	y.AssertTruef(idx >= 0, "idx=%d", idx)
 	if idx >= len(t.blockIndex) {
-		return block{}, errors.New("block out of index")
+		return nil, errors.New("block out of index")
 	}
 
 	ko := t.blockIndex[idx]
-	blk := block{
+	blk := &block{
 		offset: ko.offset,
 	}
 	var err error