improve baseDeltaBlockPostings

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

Author: naivewong

index/index.go

@@ -1082,7 +1082,7 @@ func (dec *Decoder) Postings(b []byte) (int, Postings, error) {
 		return n, newDeltaBlockPostings(l, n), d.Err()
 	case 4:
 		l := d.Get()
-		return n, newBaseDeltaBlockPostings(l, n), d.Err()
+		return n, newBaseDeltaBlockPostings(l), d.Err()
 	case 5:
 		l := d.Get()
 		return n, newBitmapPostings(l), d.Err()

index/postings.go

@@ -14,6 +14,8 @@
 package index
 
 import (
+	// "time"
+	// "fmt"
 	"container/heap"
 	"encoding/binary"
 	"math/bits"
@@ -693,7 +695,7 @@ func (it *bigEndianPostings) Err() error {
 }
 
 // 1 is bigEndian, 2 is baseDelta, 3 is deltaBlock, 4 is baseDeltaBlock, 5 is bitmapPostings, 6 is roaringBitmapPostings.
-const postingsType = 2
+const postingsType = 4
 
 type bitSlice struct {
 	bstream []byte
@@ -812,7 +814,8 @@ func (it *baseDeltaPostings) Err() error {
 	return nil
 }
 
-const deltaBlockSize = 256
+const deltaBlockSize = 32
+const deltaBlockBits = 5
 
 // Block format(delta is to the previous value).
 // ┌────────────────┬───────────────┬─────────────────┬────────────┬────────────────┬─────┬────────────────┐
@@ -970,71 +973,55 @@ func writeDeltaBlockPostings(e *encoding.Encbuf, arr []uint32) {
 }
 
 // Block format(delta is to the base).
-// ┌────────────────┬───────────────┬─────────────────┬────────────┬────────────────┬─────┬────────────────┐
-// │ base <uvarint> │ idx <uvarint> │ count <uvarint> │ width <1b> │ delta 1 <bits> │ ... │ delta n <bits> │
-// └────────────────┴───────────────┴─────────────────┴────────────┴────────────────┴─────┴────────────────┘
+// ┌────────────────┬─────────────────┬────────────┬─────────────────┬─────┬─────────────────┐
+// │ base <uvarint> │ count <uvarint> │ width <1b> │ delta 1 <bytes> │ ... │ delta n <bytes> │
+// └────────────────┴─────────────────┴────────────┴─────────────────┴─────┴─────────────────┘
 type baseDeltaBlockPostings struct {
 	bs       bitSlice
-	size     int
 	count    int // count in current block.
 	idxBlock int
 	idx      int
 	offset   int // offset in bit.
 	cur      uint64
 	base     uint64
+	mask     uint32
+	prel     int
 }
 
-func newBaseDeltaBlockPostings(bstream []byte, size int) *baseDeltaBlockPostings {
-	return &baseDeltaBlockPostings{bs: bitSlice{bstream: bstream}, size: size}
-}
-
-func (it *baseDeltaBlockPostings) GetOff() int {
-	return it.offset
-}
-func (it *baseDeltaBlockPostings) GetWidth() int {
-	return it.bs.width
+func newBaseDeltaBlockPostings(bstream []byte) *baseDeltaBlockPostings {
+	return &baseDeltaBlockPostings{bs: bitSlice{bstream: bstream}}
 }
 
 func (it *baseDeltaBlockPostings) At() uint64 {
 	return it.cur
 }
 
 func (it *baseDeltaBlockPostings) Next() bool {
-	if it.offset >= len(it.bs.bstream)<<3 || it.idx >= it.size {
+	if it.offset >= len(it.bs.bstream) {
 		return false
 	}
-	if it.offset%(deltaBlockSize<<3) == 0 {
-		val, n := binary.Uvarint(it.bs.bstream[it.offset>>3:])
-		if n < 1 {
-			return false
-		}
+	if it.offset%deltaBlockSize == 0 {
+		val, n := binary.Uvarint(it.bs.bstream[it.offset:])
 		it.cur = val
 		it.base = val
-		it.offset += n << 3
-		val, n = binary.Uvarint(it.bs.bstream[it.offset>>3:])
-		if n < 1 {
-			return false
-		}
-		it.idx = int(val) + 1
-		it.offset += n << 3
-		val, n = binary.Uvarint(it.bs.bstream[it.offset>>3:])
-		if n < 1 {
-			return false
-		}
+		it.offset += n
+
+		val, n = binary.Uvarint(it.bs.bstream[it.offset:])
 		it.count = int(val)
-		it.offset += n << 3
-		it.bs.width = int(it.bs.bstream[it.offset>>3])
-		it.offset += 8
+		it.offset += n
+		it.bs.width = int(it.bs.bstream[it.offset])
+		it.mask = (uint32(1) << uint(8 * it.bs.width)) - 1
+		it.prel = 4 - it.bs.width
+		it.offset += 1
 		it.idxBlock = 1
 		return true
 	}
 
-	it.cur = it.bs.readBits(it.offset) + it.base
+	it.cur = uint64(binary.BigEndian.Uint32(it.bs.bstream[it.offset-it.prel:])&it.mask) + it.base
 	it.offset += it.bs.width
-	it.idx += 1
 	it.idxBlock += 1
 	if it.idxBlock == it.count {
-		it.offset = ((it.offset-1)/(deltaBlockSize<<3) + 1) * deltaBlockSize << 3
+		it.offset = (((it.offset-1)>>deltaBlockBits) + 1) << deltaBlockBits
 	}
 	return true
 }
@@ -1043,69 +1030,109 @@ func (it *baseDeltaBlockPostings) Seek(x uint64) bool {
 	if it.cur >= x {
 		return true
 	}
-
-	startOff := (it.offset - 1) / (deltaBlockSize << 3) * deltaBlockSize
-	num := (len(it.bs.bstream)-1)/deltaBlockSize - (it.offset-1)/(deltaBlockSize<<3) + 1
-	// Do binary search between current position and end.
-	i := sort.Search(num, func(i int) bool {
-		val, _ := binary.Uvarint(it.bs.bstream[startOff+i*deltaBlockSize:])
-		return val > x
-	})
-	if i > 0 {
-		// Go to the previous block because the previous block
-		// may contain the first value >= x.
-		i -= 1
+	if it.offset >= len(it.bs.bstream) {
+		return false
+	}
+	startOff := (((it.offset)>>deltaBlockBits)+1)<<deltaBlockBits
+	num := (len(it.bs.bstream)>>deltaBlockBits) - (startOff>>deltaBlockBits) + 1
+	if num > 0 {
+		// Fast path to check if the binary search among blocks is needed.
+		val, _ := binary.Uvarint(it.bs.bstream[startOff:])
+		if val <= x {
+			// Do binary search between current position and end.
+			i := sort.Search(num, func(i int) bool {
+				val, _ := binary.Uvarint(it.bs.bstream[startOff+(i<<deltaBlockBits):])
+				return val > x
+			})
+			if i > 0 {
+				// Go to the previous block because the previous block
+				// may contain the first value >= x.
+				i -= 1
+			}
+			it.offset = startOff + (i<<deltaBlockBits)
+
+			// Read base, and width.
+			val, n := binary.Uvarint(it.bs.bstream[it.offset:])
+			it.cur = val
+			it.base = val
+			it.offset += n
+			val, n = binary.Uvarint(it.bs.bstream[it.offset:])
+			it.count = int(val)
+			it.offset += n
+			it.bs.width = int(it.bs.bstream[it.offset])
+			it.mask = (uint32(1) << uint(8 * it.bs.width)) - 1
+			it.prel = 4 - it.bs.width
+			it.offset += 1
+			it.idxBlock = 1
+			if x <= it.base {
+				return true
+			} else {
+				temp := x - it.base
+				j := sort.Search(it.count-it.idxBlock, func(i int) bool {
+					return uint64(binary.BigEndian.Uint32(it.bs.bstream[it.offset+i*it.bs.width-it.prel:])&it.mask) >= temp
+				})
+				if j < it.count-it.idxBlock {
+					it.offset += j * it.bs.width
+					it.cur = uint64(binary.BigEndian.Uint32(it.bs.bstream[it.offset-it.prel:])&it.mask) + it.base
+					it.idxBlock += j + 1
+					if it.idxBlock == it.count {
+						// it.offset = startOff + ((i+1)<<deltaBlockBits)
+						it.offset = ((startOff>>deltaBlockBits)+i+1)<<deltaBlockBits
+					} else {
+						it.offset += it.bs.width
+					}
+				} else {
+					// it.offset = startOff + ((i+1)<<deltaBlockBits)
+					it.offset = ((startOff>>deltaBlockBits)+i+1)<<deltaBlockBits
+					return it.Next()
+				}
+				return true
+			}
+		}
 	}
 
-	if i == 0 && it.idx > 0 {
+	// Search in current block.
+	startOff -= deltaBlockSize
+	if it.offset == startOff {
+		// Read base, and width.
+		val, n := binary.Uvarint(it.bs.bstream[it.offset:])
+		it.cur = val
+		it.base = val
+		it.offset += n
+		val, n = binary.Uvarint(it.bs.bstream[it.offset:])
+		it.count = int(val)
+		it.offset += n
+		it.bs.width = int(it.bs.bstream[it.offset])
+		it.mask = (uint32(1) << uint(8 * it.bs.width)) - 1
+		it.prel = 4 - it.bs.width
+		it.offset += 1
+		it.idxBlock = 1
+	}
+	if x <= it.base {
+		return true
+	} else {
 		temp := x - it.base
 		j := sort.Search(it.count-it.idxBlock, func(i int) bool {
-			return it.bs.readBits(it.offset+i*it.bs.width) >= temp
+			return uint64(binary.BigEndian.Uint32(it.bs.bstream[it.offset+i*it.bs.width-it.prel:])&it.mask) >= temp
 		})
-
 		if j < it.count-it.idxBlock {
 			it.offset += j * it.bs.width
-			it.cur = it.bs.readBits(it.offset) + it.base
-			it.offset += it.bs.width
+			it.cur = uint64(binary.BigEndian.Uint32(it.bs.bstream[it.offset-it.prel:])&it.mask) + it.base
 			it.idxBlock += j + 1
-			it.idx += j + 1
 			if it.idxBlock == it.count {
-				it.offset = ((it.offset-1)/(deltaBlockSize<<3) + 1) * deltaBlockSize << 3
+				// it.offset = startOff + deltaBlockSize
+				it.offset = ((startOff>>deltaBlockBits)+1)<<deltaBlockBits
+			} else {
+				it.offset += it.bs.width
 			}
 		} else {
-			it.offset = (startOff + (i+1)*deltaBlockSize) << 3
+			// it.offset = startOff + deltaBlockSize
+			it.offset = ((startOff>>deltaBlockBits)+1)<<deltaBlockBits
 			return it.Next()
 		}
 		return true
-	} else {
-		it.offset = (startOff + i*deltaBlockSize) << 3
-
-		// Read base, idx, and width.
-		it.Next()
-		if x <= it.base {
-			return true
-		} else {
-			temp := x - it.base
-			j := sort.Search(it.count-it.idxBlock, func(i int) bool {
-				return it.bs.readBits(it.offset+i*it.bs.width) >= temp
-			})
-
-			if j < it.count-it.idxBlock {
-				it.offset += j * it.bs.width
-				it.cur = it.bs.readBits(it.offset) + it.base
-				it.offset += it.bs.width
-				it.idxBlock += j + 1
-				it.idx += j + 1
-				if it.idxBlock == it.count {
-					it.offset = ((it.offset-1)/(deltaBlockSize<<3) + 1) * deltaBlockSize << 3
-				}
-			} else {
-				it.offset = (startOff + (i+1)*deltaBlockSize) << 3
-				return it.Next()
-			}
-			return true
-		}
 	}
+	
 }
 
 func (it *baseDeltaBlockPostings) Err() error {
@@ -1121,16 +1148,18 @@ func writeBaseDeltaBlockPostings(e *encoding.Encbuf, arr []uint32) {
 	var max int
 	for i < len(arr) {
 		e.PutUvarint32(arr[i])    // Put base.
-		e.PutUvarint64(uint64(i)) // Put idx.
-		remaining = (deltaBlockSize - (len(e.B)-startLen)%deltaBlockSize - 1) << 3
+		remaining = deltaBlockSize - (len(e.B)-startLen)%deltaBlockSize - 1
 		deltas = deltas[:0]
 		base = arr[i]
 		max = -1
 		i += 1
 		for i < len(arr) {
 			delta := arr[i] - base
-			cur := bits.Len32(delta)
-			if remaining-cur*(len(deltas)+1)-(((bits.Len(uint(len(deltas)))>>3)+1)<<3) >= 0 {
+			cur := (bits.Len32(delta) + 7) >> 3
+			if cur == 0 {
+				cur = 1
+			}
+			if remaining-cur*(len(deltas)+1)-((bits.Len(uint(len(deltas)))>>3)+1) >= 0 {
 				deltas = append(deltas, delta)
 				max = cur
 			} else {
@@ -1140,28 +1169,22 @@ func writeBaseDeltaBlockPostings(e *encoding.Encbuf, arr []uint32) {
 		}
 		e.PutUvarint64(uint64(len(deltas) + 1))
 		e.PutByte(byte(max))
-		remaining -= ((bits.Len(uint(len(deltas))) >> 3) + 1) << 3
+		remaining -= ((bits.Len(uint(len(deltas))) >> 3) + 1)
 		for _, delta := range deltas {
-			e.PutBits(uint64(delta), max)
+			for j := max - 1; j >= 0; j-- {
+				e.B = append(e.B, byte((delta>>(8*uint(j))&0xff)))
+			}
 			remaining -= max
 		}
 
 		if i == len(arr) {
 			break
 		}
 
-		for remaining >= 64 {
-			e.PutBits(uint64(0), 64)
-			remaining -= 64
-		}
-
-		if remaining > 0 {
-			e.PutBits(uint64(0), remaining)
+		for remaining > 0 {
+			e.PutByte(0)
+			remaining -= 1
 		}
-		e.Count = 0
-
-		// There can be one more extra 0.
-		e.B = e.B[:len(e.B)-(len(e.B)-startLen)%deltaBlockSize]
 	}
 }