Documentation
¶
Overview ¶
Package index constructs a Bloom filter index for a set of string keys.
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
Types ¶
type Index ¶
type Index struct {
// contains filtered or unexported fields
}
An Index holds a Bloom filter index for a set of keys.
Example ¶
package main
import (
"fmt"
"strings"
"github.com/creachadair/ffs/index"
)
func main() {
words := strings.Fields("a foolish consistency is the hobgoblin of little minds")
idx := index.New(32, nil)
for _, word := range words {
idx.Add(word)
}
fmt.Printf("Has %q: %v\n", "foolish", idx.Has("foolish"))
fmt.Printf("Has %q: %v\n", "cabbage", idx.Has("cabbage"))
info := idx.Stats()
fmt.Printf("%d keys, %d filter bits, %d hash seeds\n",
info.NumKeys, info.FilterBits, info.NumHashes)
}
Output: Has "foolish": true Has "cabbage": false 9 keys, 256 filter bits, 6 hash seeds
func New ¶
New constructs an empty index with capacity for the specified number of keys. A nil opts value is ready for use and provides default values as described on Options. New will panic if numKeys ≤ 0.
func (*Index) Has ¶
Has reports whether key is one of the indexed keys. False positives are possible for keys that were not added to the index, but no false negatives.
type Options ¶
type Options struct {
// Compute a 64-bit hash of s. If nil, uses xxhash.Sum64String.
Hash func(s string) uint64
// The maximum false positive rate to permit. A value ≤ 0 defaults to 0.03.
// Decreasing this value increases the memory required for the index.
FalsePositiveRate float64
}
Options provide optional settings for an index. A nil *Options is ready for use and provides default values as described.
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