Tweaks.

Author: ncruces

ext/bloom/bloom.go

@@ -30,7 +30,7 @@ type bloom struct {
 	schema  string
 	storage string
 	prob    float64
-	nfilter int64
+	bytes   int64
 	hashes  int
 }
 
@@ -41,15 +41,17 @@ func create(db *sqlite3.Conn, _, schema, table string, arg ...string) (_ *bloom,
 		storage: table + "_storage",
 	}
 
-	nelem := 100
+	var nelem int64
 	if len(arg) > 0 {
-		nelem, err = strconv.Atoi(arg[0])
+		nelem, err = strconv.ParseInt(arg[0], 10, 64)
 		if err != nil {
 			return nil, err
 		}
 		if nelem <= 0 {
 			return nil, errors.New("bloom: number of elements in filter must be positive")
 		}
+	} else {
+		nelem = 100
 	}
 
 	if len(arg) > 1 {
@@ -73,10 +75,10 @@ func create(db *sqlite3.Conn, _, schema, table string, arg ...string) (_ *bloom,
 			return nil, errors.New("bloom: number of hash functions must be positive")
 		}
 	} else {
-		t.hashes = int(math.Round(-math.Log2(t.prob)))
+		t.hashes = max(1, numHashes(t.prob))
 	}
 
-	t.nfilter = computeLength(nelem, t.prob)
+	t.bytes = numBytes(nelem, t.prob)
 
 	err = db.Exec(fmt.Sprintf(
 		`CREATE TABLE %s.%s (data BLOB, p REAL, n INTEGER, m INTEGER, k INTEGER)`,
@@ -89,7 +91,7 @@ func create(db *sqlite3.Conn, _, schema, table string, arg ...string) (_ *bloom,
 		`INSERT INTO %s.%s (rowid, data, p, n, m, k)
 		 VALUES (1, zeroblob(%d), %f, %d, %d, %d)`,
 		sqlite3.QuoteIdentifier(t.schema), sqlite3.QuoteIdentifier(t.storage),
-		t.nfilter, t.prob, nelem, t.nfilter*8, t.hashes))
+		t.bytes, t.prob, nelem, 8*t.bytes, t.hashes))
 	if err != nil {
 		return nil, err
 	}
@@ -131,7 +133,7 @@ func connect(db *sqlite3.Conn, _, schema, table string, arg ...string) (_ *bloom
 		return nil, err
 	}
 
-	t.nfilter = load.ColumnInt64(0)
+	t.bytes = load.ColumnInt64(0)
 	t.prob = load.ColumnFloat(1)
 	t.hashes = load.ColumnInt(2)
 	return &t, nil
@@ -188,7 +190,7 @@ func (b *bloom) Update(arg ...sqlite3.Value) (rowid int64, err error) {
 
 	for n := 0; n < b.hashes; n++ {
 		hash := calcHash(n, blob)
-		hash %= uint64(b.nfilter * 8)
+		hash %= uint64(b.bytes * 8)
 		bitpos := byte(hash % 8)
 		bytepos := int64(hash / 8)
 
@@ -202,7 +204,7 @@ func (b *bloom) Update(arg ...sqlite3.Value) (rowid int64, err error) {
 			return 0, err
 		}
 
-		buf[0] |= (1 << bitpos)
+		buf[0] |= 1 << bitpos
 
 		_, err = f.Seek(bytepos, io.SeekStart)
 		if err != nil {
@@ -241,9 +243,9 @@ func (c *cursor) Filter(idxNum int, idxStr string, arg ...sqlite3.Value) error {
 	}
 	defer f.Close()
 
-	for n := 0; n < c.hashes; n++ {
+	for n := 0; n < c.hashes && !c.eof; n++ {
 		hash := calcHash(n, blob)
-		hash %= uint64(c.nfilter * 8)
+		hash %= uint64(c.bytes * 8)
 		bitpos := byte(hash % 8)
 		bytepos := int64(hash / 8)
 
@@ -257,10 +259,7 @@ func (c *cursor) Filter(idxNum int, idxStr string, arg ...sqlite3.Value) error {
 			return err
 		}
 
-		c.eof = (buf[0] & (1 << bitpos)) == 0
-		if c.eof {
-			break
-		}
+		c.eof = buf[0]&(1<<bitpos) == 0
 	}
 	return nil
 }
@@ -294,7 +293,12 @@ func calcHash(k int, b []byte) uint64 {
 	return siphash.Hash(^uint64(k), uint64(k), b)
 }
 
-func computeLength(n int, p float64) int64 {
-	bits := math.Ceil(-((float64(n) * math.Log(p)) / (math.Ln2 * math.Ln2)))
-	return (int64(bits) + 7) / 8
+func numHashes(p float64) int {
+	k := math.Round(-math.Log2(p))
+	return max(1, int(k))
+}
+
+func numBytes(n int64, p float64) int64 {
+	m := math.Ceil(float64(n) * math.Log(p) / -(math.Ln2 * math.Ln2))
+	return (int64(m) + 7) / 8
 }