Fix Get() return status when block cache is disabled (#8485)

Summary:
This PR is for https://github.com/facebook/rocksdb/issues/8453

We need to update `s = biter.status();`  when `biter.status().IsIncomplete()` is true. By doing this, can fix the problem in issue.
Besides, we still need to update `db_statistics`  in `get_context.ReportCounters()` before return back.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8485

Reviewed By: jay-zhuang

Differential Revision: D29604835

Pulled By: ajkr

fbshipit-source-id: c7f2f1cd058223ce1b507ec05d57cf264b9c9710

HISTORY.md

@@ -8,6 +8,8 @@
 * `GetLiveFilesMetaData()` now populates the `temperature`, `oldest_ancester_time`, and `file_creation_time` fields of its `LiveFileMetaData` results when the information is available. Previously these fields always contained zero indicating unknown.
 * Fix mismatches of OnCompaction{Begin,Completed} in case of DisableManualCompaction().
 * Fix continuous logging of an existing background error on every user write
+* Fix a bug that `Get()` return Status::OK() and an empty value for non-existent key when `read_options.read_tier = kBlockCacheTier`. 
+* Fix a bug that stat in `get_context` didn't accumulate to statistics when query is failed.
 
 ### New Features
 * ldb has a new feature, `list_live_files_metadata`, that shows the live SST files, as well as their LSM storage level and the column family they belong to.

db/db_block_cache_test.cc

@@ -299,8 +299,8 @@ TEST_F(DBBlockCacheTest, TestWithCompressedBlockCache) {
   // Load last key block.
   ASSERT_EQ("Result incomplete: Insert failed due to LRU cache being full.",
             Get(ToString(kNumBlocks - 1)));
-  // Failure won't record the miss counter.
+  // Failure will also record the miss counter.
-  CheckCacheCounters(options, 0, 0, 0, 1);
+  CheckCacheCounters(options, 1, 0, 0, 1);
   CheckCompressedCacheCounters(options, 1, 0, 1, 0);
 
   // Clear strict capacity limit flag. This time we shall hit compressed block

db/version_set.cc

@@ -1939,6 +1939,9 @@ void Version::Get(const ReadOptions& read_options, const LookupKey& k,
                                 fp.GetHitFileLevel());
     }
     if (!status->ok()) {
+      if (db_statistics_ != nullptr) {
+        get_context.ReportCounters();
+      }
       return;
     }
 

table/block_based/block_based_table_reader.cc

@@ -2341,6 +2341,7 @@ Status BlockBasedTable::Get(const ReadOptions& read_options, const Slice& key,
         // Update Saver.state to Found because we are only looking for
         // whether we can guarantee the key is not there when "no_io" is set
         get_context->MarkKeyMayExist();
+        s = biter.status();
         break;
       }
       if (!biter.status().ok()) {