Add bloom filter to predefined table stats

Summary: As title.

Test Plan: Updated the unit tests to make sure new statistic is correctly written/read.

Reviewers: dhruba, haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D13497

include/rocksdb/table_stats.h

@@ -35,6 +35,10 @@ struct TableStats {
   // the number of entries in this table
   uint64_t num_entries = 0;
 
+  // The name of the filter policy used in this table.
+  // If no filter policy is used, `filter_policy_name` will be an empty string.
+  std::string filter_policy_name;
+
   // user collected stats
   UserCollectedStats user_collected_stats;
 };

table/table.cc

@@ -269,7 +269,8 @@ Status Table::ReadStats(const Slice& handle_value, Rep* rep) {
   );
 
   auto& table_stats = rep->table_stats;
-  std::unordered_map<std::string, uint64_t*> predefined_name_stat_map = {
+  // All pre-defined stats of type uint64_t
+  std::unordered_map<std::string, uint64_t*> predefined_uint64_stats = {
     { TableStatsNames::kDataSize,      &table_stats.data_size       },
     { TableStatsNames::kIndexSize,     &table_stats.index_size      },
     { TableStatsNames::kRawKeySize,    &table_stats.raw_key_size    },
@@ -294,14 +295,9 @@ Status Table::ReadStats(const Slice& handle_value, Rep* rep) {
     last_key = key;
 
     auto raw_val = iter->value();
-    auto pos = predefined_name_stat_map.find(key);
+    auto pos = predefined_uint64_stats.find(key);
 
-    if (pos == predefined_name_stat_map.end()) {
-      // handle user-collected
-      table_stats.user_collected_stats.insert(
-          std::make_pair(iter->key().ToString(), raw_val.ToString())
-      );
-    } else {
+    if (pos != predefined_uint64_stats.end()) {
       // handle predefined rocksdb stats
       uint64_t val;
       if (!GetVarint64(&raw_val, &val)) {
@@ -313,6 +309,13 @@ Status Table::ReadStats(const Slice& handle_value, Rep* rep) {
         continue;
       }
       *(pos->second) = val;
+    } else if (key == TableStatsNames::kFilterPolicy) {
+      table_stats.filter_policy_name = raw_val.ToString();
+    } else {
+      // handle user-collected
+      table_stats.user_collected_stats.insert(
+          std::make_pair(iter->key().ToString(), raw_val.ToString())
+      );
     }
   }
 
@@ -608,5 +611,6 @@ const std::string TableStatsNames::kRawKeySize = "rocksdb.raw.key.size";
 const std::string TableStatsNames::kRawValueSize  = "rocksdb.raw.value.size";
 const std::string TableStatsNames::kNumDataBlocks = "rocksdb.num.data.blocks";
 const std::string TableStatsNames::kNumEntries    = "rocksdb.num.entries";
+const std::string TableStatsNames::kFilterPolicy  = "rocksdb.filter.policy";
 
 }  // namespace rocksdb

table/table.h

@@ -120,6 +120,7 @@ struct TableStatsNames {
   static const std::string kRawValueSize;
   static const std::string kNumDataBlocks;
   static const std::string kNumEntries;
+  static const std::string kFilterPolicy;
 };
 
 }  // namespace rocksdb

table/table_builder.cc

@@ -368,6 +368,12 @@ Status TableBuilder::Finish() {
       );
       AddStats(stats, TableStatsNames::kNumEntries, r->num_entries);
       AddStats(stats, TableStatsNames::kNumDataBlocks, r->num_data_blocks);
+      if (r->filter_block != nullptr) {
+        stats.insert(std::make_pair(
+              TableStatsNames::kFilterPolicy,
+              r->options.filter_policy->Name()
+        ));
+      }
 
       for (const auto& stat : stats) {
         stats_block.Add(stat.first, stat.second);

table/table_test.cc

@@ -886,6 +886,7 @@ TEST(TableTest, BasicTableStats) {
   ASSERT_EQ(raw_key_size, stats.raw_key_size);
   ASSERT_EQ(raw_value_size, stats.raw_value_size);
   ASSERT_EQ(1ul, stats.num_data_blocks);
+  ASSERT_EQ("", stats.filter_policy_name);  // no filter policy is used
 
   // Verify data size.
   BlockBuilder block_builder(&options);
@@ -899,6 +900,19 @@ TEST(TableTest, BasicTableStats) {
   );
 }
 
+TEST(TableTest, FilterPolicyNameStats) {
+  TableConstructor c(BytewiseComparator());
+  c.Add("a1", "val1");
+  std::vector<std::string> keys;
+  KVMap kvmap;
+  Options options;
+  options.filter_policy = NewBloomFilterPolicy(10);
+
+  c.Finish(options, &keys, &kvmap);
+  auto& stats = c.table()->GetTableStats();
+  ASSERT_EQ("rocksdb.BuiltinBloomFilter", stats.filter_policy_name);
+}
+
 static std::string RandomString(Random* rnd, int len) {
   std::string r;
   test::RandomString(rnd, len, &r);