Init compression dict handle before reading meta-blocks (#5267)

Summary:
At least one of the meta-block loading functions (`ReadRangeDelBlock`)
uses the same block reading function (`NewDataBlockIterator`) as data
block reads, which means it uses the dictionary handle. However, the
dictionary handle was uninitialized while reading meta-blocks, causing
readers to receive an error. This situation was only noticed when
`cache_index_and_filter_blocks=true`.

This PR initializes the handle to null while reading meta-blocks to
prevent the error. It also adds support to `db_stress` /
`db_crashtest.py` for `cache_index_and_filter_blocks`.

Fixes #5263.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5267

Differential Revision: D15149264

Pulled By: maysamyabandeh

fbshipit-source-id: 991d38a306c62db5976778bfb050fa3cd4a0671b

table/block_based_table_reader.cc

@@ -838,6 +838,11 @@ Status BlockBasedTable::Open(const ImmutableCFOptions& ioptions,
                                          rep->persistent_cache_key_prefix_size),
                              rep->ioptions.statistics);
 
+  // Meta-blocks are not dictionary compressed. Explicitly set the dictionary
+  // handle to null, otherwise it may be seen as uninitialized during the below
+  // meta-block reads.
+  rep->compression_dict_handle = BlockHandle::NullBlockHandle();
+
   // Read metaindex
   std::unique_ptr<Block> meta;
   std::unique_ptr<InternalIterator> meta_iter;

tools/db_crashtest.py

@@ -25,6 +25,7 @@ expected_values_file = tempfile.NamedTemporaryFile()
 default_params = {
     "acquire_snapshot_one_in": 10000,
     "block_size": 16384,
+    "cache_index_and_filter_blocks": lambda: random.randint(0, 1),
     "cache_size": 1048576,
     "checkpoint_one_in": 1000000,
     "compression_type": "snappy",

tools/db_stress.cc

@@ -297,6 +297,9 @@ DEFINE_int32(set_in_place_one_in, 0,
 DEFINE_int64(cache_size, 2LL * KB * KB * KB,
              "Number of bytes to use as a cache of uncompressed data.");
 
+DEFINE_bool(cache_index_and_filter_blocks, false,
+            "True if indexes/filters should be cached in block cache.");
+
 DEFINE_bool(use_clock_cache, false,
             "Replace default LRU block cache with clock cache.");
 
@@ -2578,6 +2581,8 @@ class StressTest {
     if (FLAGS_options_file.empty()) {
       BlockBasedTableOptions block_based_options;
       block_based_options.block_cache = cache_;
+      block_based_options.cache_index_and_filter_blocks =
+          FLAGS_cache_index_and_filter_blocks;
       block_based_options.block_cache_compressed = compressed_cache_;
       block_based_options.checksum = FLAGS_checksum_type_e;
       block_based_options.block_size = FLAGS_block_size;