Clean up obsolete code in BlockBasedTable::PrefetchIndexAndFilterBloc…

…ks (#13277)

Summary:
As advertised and recommended by original authors comment, we're removing the now-outdated special handling logic for bloom filters perf regression (timing ~release 7.0.X). I decided to keep the `CompatibilityName` as-is since 1) it's publicly exposed API and 2) it's generally useful to have a dedicated name used for identifying whether a filter on disk is readable by the FilterPolicy.

Pull Request resolved: #13277

Test Plan:
'Dead code' / tech debt. As a smoke test, I manually run a similar benchmark to the one in #9736, with ./db_bench built pre and post change.

**Generate DB:**

```hcl
./db_bench -db=/dev/shm/rocksdb.9.11 -bloom_bits=10 -cache_index_and_filter_blocks=1 -benchmarks=fillrandom -num=10000000 -compaction_style=2 -fifo_compaction_max_table_files_size_mb=10000 -fifo_compaction_allow_compaction=0
```

**Before removing the 'if' block:**

```hcl
./db_bench -db=/dev/shm/rocksdb.9.11 -use_existing_db -readonly -bloom_bits=10 -benchmarks=readrandom -num=10000000 -compaction_style=2 -fifo_compaction_max_table_files_size_mb=10000 -fifo_compaction_allow_compaction=0 -duration=10 2>&1 | grep micros/op

readrandom   :      17.216 micros/op 58085 ops/sec 10.002 seconds 580999 operations;    4.1 MB/s (367256 of 580999 found)
```

**After removing the 'if' block:**

```hcl
./db_bench -db=/dev/shm/rocksdb.9.11 -use_existing_db -readonly -bloom_bits=10 -benchmarks=readrandom -num=10000000 -compaction_style=2 -fifo_compaction_max_table_files_size_mb=10000 -fifo_compaction_allow_compaction=0 -duration=10 2>&1 | grep micros/op

readrandom   :      16.776 micros/op 59607 ops/sec 10.015 seconds 596999 operations;    4.2 MB/s (377846 of 596999 found)
```

Reviewed By: jaykorean, pdillinger

Differential Revision: D67908020

Pulled By: mszeszko-meta

fbshipit-source-id: b904b8eaf9d106f0b47e4ff175242795ac1c5e73

table/block_based/block_based_table_reader.cc

@@ -1107,71 +1107,24 @@ Status BlockBasedTable::PrefetchIndexAndFilterBlocks(
   // Find filter handle and filter type
   if (rep_->filter_policy) {
     auto name = rep_->filter_policy->CompatibilityName();
-    bool builtin_compatible =
-        strcmp(name, BuiltinFilterPolicy::kCompatibilityName()) == 0;
-
     for (const auto& [filter_type, prefix] :
          {std::make_pair(Rep::FilterType::kFullFilter, kFullFilterBlockPrefix),
           std::make_pair(Rep::FilterType::kPartitionedFilter,
                          kPartitionedFilterBlockPrefix),
           std::make_pair(Rep::FilterType::kNoFilter,
                          kObsoleteFilterBlockPrefix)}) {
-      if (builtin_compatible) {
-        // This code is only here to deal with a hiccup in early 7.0.x where
-        // there was an unintentional name change in the SST files metadata.
-        // It should be OK to remove this in the future (late 2022) and just
-        // have the 'else' code.
-        // NOTE: the test:: names below are likely not needed but included
-        // out of caution
-        static const std::unordered_set<std::string> kBuiltinNameAndAliases = {
-            BuiltinFilterPolicy::kCompatibilityName(),
-            test::LegacyBloomFilterPolicy::kClassName(),
-            test::FastLocalBloomFilterPolicy::kClassName(),
-            test::Standard128RibbonFilterPolicy::kClassName(),
-            "rocksdb.internal.DeprecatedBlockBasedBloomFilter",
-            BloomFilterPolicy::kClassName(),
-            RibbonFilterPolicy::kClassName(),
-        };
-
-        // For efficiency, do a prefix seek and see if the first match is
-        // good.
-        meta_iter->Seek(prefix);
-        if (meta_iter->status().ok() && meta_iter->Valid()) {
-          Slice key = meta_iter->key();
-          if (key.starts_with(prefix)) {
-            key.remove_prefix(prefix.size());
-            if (kBuiltinNameAndAliases.find(key.ToString()) !=
-                kBuiltinNameAndAliases.end()) {
-              Slice v = meta_iter->value();
-              Status s = rep_->filter_handle.DecodeFrom(&v);
-              if (s.ok()) {
-                rep_->filter_type = filter_type;
-                if (filter_type == Rep::FilterType::kNoFilter) {
-                  ROCKS_LOG_WARN(rep_->ioptions.logger,
-                                 "Detected obsolete filter type in %s. Read "
-                                 "performance might suffer until DB is fully "
-                                 "re-compacted.",
-                                 rep_->file->file_name().c_str());
-                }
-                break;
-              }
-            }
-          }
-        }
-      } else {
-        std::string filter_block_key = prefix + name;
-        if (FindMetaBlock(meta_iter, filter_block_key, &rep_->filter_handle)
-                .ok()) {
-          rep_->filter_type = filter_type;
-          if (filter_type == Rep::FilterType::kNoFilter) {
-            ROCKS_LOG_WARN(
-                rep_->ioptions.logger,
-                "Detected obsolete filter type in %s. Read performance might "
-                "suffer until DB is fully re-compacted.",
-                rep_->file->file_name().c_str());
-          }
-          break;
+      std::string filter_block_key = prefix + name;
+      if (FindMetaBlock(meta_iter, filter_block_key, &rep_->filter_handle)
+              .ok()) {
+        rep_->filter_type = filter_type;
+        if (filter_type == Rep::FilterType::kNoFilter) {
+          ROCKS_LOG_WARN(
+              rep_->ioptions.logger,
+              "Detected obsolete filter type in %s. Read performance might "
+              "suffer until DB is fully re-compacted.",
+              rep_->file->file_name().c_str());
         }
+        break;
       }
     }
   }

table/block_based/filter_policy.cc

@@ -1410,10 +1410,6 @@ bool BuiltinFilterPolicy::IsInstanceOf(const std::string& name) const {
 
 static const char* kBuiltinFilterMetadataName = "rocksdb.BuiltinBloomFilter";
 
-const char* BuiltinFilterPolicy::kCompatibilityName() {
-  return kBuiltinFilterMetadataName;
-}
-
 const char* BuiltinFilterPolicy::CompatibilityName() const {
   return kBuiltinFilterMetadataName;
 }

table/block_based/filter_policy_internal.h

@@ -149,7 +149,6 @@ class BuiltinFilterPolicy : public FilterPolicy {
   bool IsInstanceOf(const std::string& id) const override;
   // All variants of BuiltinFilterPolicy can read each others filters.
   const char* CompatibilityName() const override;
-  static const char* kCompatibilityName();
 
  public:  // new
   // An internal function for the implementation of