Add kHashSearch to stress tests (#6210)

Summary:
Beside extending index_type to kHashSearch, it clarifies in the code base that this feature is incompatible with index_block_restart_interval > 1.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6210

Test Plan:
```
make -j32 crash_test

Differential Revision: D19166567

Pulled By: maysamyabandeh

fbshipit-source-id: 3aaf75a70a8b462d372d43aac69dbd10df303ec7

table/block_based/block_based_table_factory.cc

@@ -157,6 +157,8 @@ size_t TailPrefetchStats::GetSuggestedPrefetchSize() {
   return std::min(kMaxPrefetchSize, max_qualified_size);
 }
 
+// TODO(myabandeh): We should return an error instead of silently changing the
+// options
 BlockBasedTableFactory::BlockBasedTableFactory(
     const BlockBasedTableOptions& _table_options)
     : table_options_(_table_options) {
@@ -184,6 +186,11 @@ BlockBasedTableFactory::BlockBasedTableFactory(
   if (table_options_.index_block_restart_interval < 1) {
     table_options_.index_block_restart_interval = 1;
   }
+  if (table_options_.index_type == BlockBasedTableOptions::kHashSearch &&
+      table_options_.index_block_restart_interval != 1) {
+    // Currently kHashSearch is incompatible with index_block_restart_interval > 1
+    table_options_.index_block_restart_interval = 1;
+  }
   if (table_options_.partition_filters &&
       table_options_.index_type !=
           BlockBasedTableOptions::kTwoLevelIndexSearch) {

table/block_based/index_builder.cc

@@ -39,6 +39,9 @@ IndexBuilder* IndexBuilder::CreateIndexBuilder(
           table_opt.index_shortening, /* include_first_key */ false);
     } break;
     case BlockBasedTableOptions::kHashSearch: {
+      // Currently kHashSearch is incompatible with index_block_restart_interval
+      // > 1
+      assert(table_opt.index_block_restart_interval == 1);
       result = new HashIndexBuilder(
           comparator, int_key_slice_transform,
           table_opt.index_block_restart_interval, table_opt.format_version,

tools/db_crashtest.py

@@ -47,7 +47,7 @@ default_params = {
     "expected_values_path": expected_values_file.name,
     "flush_one_in": 1000000,
     # Temporarily disable hash index
-    "index_type": lambda: random.choice([0,2]),
+    "index_type": lambda: random.randint(0,2),
     "max_background_compactions": 20,
     "max_bytes_for_level_base": 10485760,
     "max_key": 100000000,
@@ -226,6 +226,12 @@ def finalize_and_sanitize(src_params):
             dest_params["partition_filters"] = 0
         else:
             dest_params["use_block_based_filter"] = 0
+    # kHashSearch is incompatible with index_block_restart_interval > 1
+    if dest_params["index_type"] == 1:
+        dest_params["index_block_restart_interval"] = 1;
+        # KHashSearch need prefix_extractor to be set
+        if dest_params.get("prefix_size", 0) < 1:
+             dest_params["prefix_size"] = 3;
     if dest_params.get("atomic_flush", 0) == 1:
         # disable pipelined write when atomic flush is used.
         dest_params["enable_pipelined_write"] = 0