Line data    Source code

       1             : // Copyright 2011 The LevelDB-Go and Pebble Authors. All rights reserved. Use
       2             : // of this source code is governed by a BSD-style license that can be found in
       3             : // the LICENSE file.
       4             : 
       5             : package sstable
       6             : 
       7             : import "sync/atomic"
       8             : 
       9             : // FilterMetrics holds metrics for the filter policy.
      10             : type FilterMetrics struct {
      11             :         // The number of hits for the filter policy. This is the
      12             :         // number of times the filter policy was successfully used to avoid access
      13             :         // of a data block.
      14             :         Hits int64
      15             :         // The number of misses for the filter policy. This is the number of times
      16             :         // the filter policy was checked but was unable to filter an access of a data
      17             :         // block.
      18             :         Misses int64
      19             : }
      20             : 
      21             : // FilterMetricsTracker is used to keep track of filter metrics. It contains the
      22             : // same metrics as FilterMetrics, but they can be updated atomically. An
      23             : // instance of FilterMetricsTracker can be passed to a Reader as a ReaderOption.
      24             : type FilterMetricsTracker struct {
      25             :         // See FilterMetrics.Hits.
      26             :         hits atomic.Int64
      27             :         // See FilterMetrics.Misses.
      28             :         misses atomic.Int64
      29             : }
      30             : 
      31             : var _ ReaderOption = (*FilterMetricsTracker)(nil)
      32             : 
      33           2 : func (m *FilterMetricsTracker) readerApply(r *Reader) {
      34           2 :         if r.tableFilter != nil {
      35           2 :                 r.tableFilter.metrics = m
      36           2 :         }
      37             : }
      38             : 
      39             : // Load returns the current values as FilterMetrics.
      40           2 : func (m *FilterMetricsTracker) Load() FilterMetrics {
      41           2 :         return FilterMetrics{
      42           2 :                 Hits:   m.hits.Load(),
      43           2 :                 Misses: m.misses.Load(),
      44           2 :         }
      45           2 : }
      46             : 
      47             : // BlockHandle is the file offset and length of a block.
      48             : type BlockHandle struct {
      49             :         Offset, Length uint64
      50             : }
      51             : 
      52             : // BlockHandleWithProperties is used for data blocks and first/lower level
      53             : // index blocks, since they can be annotated using BlockPropertyCollectors.
      54             : type BlockHandleWithProperties struct {
      55             :         BlockHandle
      56             :         Props []byte
      57             : }
      58             : 
      59             : type filterWriter interface {
      60             :         addKey(key []byte)
      61             :         finish() ([]byte, error)
      62             :         metaName() string
      63             :         policyName() string
      64             : }
      65             : 
      66             : type tableFilterReader struct {
      67             :         policy  FilterPolicy
      68             :         metrics *FilterMetricsTracker
      69             : }
      70             : 
      71           2 : func newTableFilterReader(policy FilterPolicy) *tableFilterReader {
      72           2 :         return &tableFilterReader{
      73           2 :                 policy:  policy,
      74           2 :                 metrics: nil,
      75           2 :         }
      76           2 : }
      77             : 
      78           2 : func (f *tableFilterReader) mayContain(data, key []byte) bool {
      79           2 :         mayContain := f.policy.MayContain(TableFilter, data, key)
      80           2 :         if f.metrics != nil {
      81           2 :                 if mayContain {
      82           2 :                         f.metrics.misses.Add(1)
      83           2 :                 } else {
      84           2 :                         f.metrics.hits.Add(1)
      85           2 :                 }
      86             :         }
      87           2 :         return mayContain
      88             : }
      89             : 
      90             : type tableFilterWriter struct {
      91             :         policy FilterPolicy
      92             :         writer FilterWriter
      93             :         // count is the count of the number of keys added to the filter.
      94             :         count int
      95             : }
      96             : 
      97           2 : func newTableFilterWriter(policy FilterPolicy) *tableFilterWriter {
      98           2 :         return &tableFilterWriter{
      99           2 :                 policy: policy,
     100           2 :                 writer: policy.NewWriter(TableFilter),
     101           2 :         }
     102           2 : }
     103             : 
     104           2 : func (f *tableFilterWriter) addKey(key []byte) {
     105           2 :         f.count++
     106           2 :         f.writer.AddKey(key)
     107           2 : }
     108             : 
     109           2 : func (f *tableFilterWriter) finish() ([]byte, error) {
     110           2 :         if f.count == 0 {
     111           2 :                 return nil, nil
     112           2 :         }
     113           2 :         return f.writer.Finish(nil), nil
     114             : }
     115             : 
     116           2 : func (f *tableFilterWriter) metaName() string {
     117           2 :         return "fullfilter." + f.policy.Name()
     118           2 : }
     119             : 
     120           2 : func (f *tableFilterWriter) policyName() string {
     121           2 :         return f.policy.Name()
     122           2 : }