Fix coverity issues version, write_batch

Summary:
db/version_builder.cc:
117        base_vstorage_->InternalComparator();

CID 1351713 (#1 of 1): Uninitialized pointer field (UNINIT_CTOR)
2. uninit_member: Non-static class member field level_zero_cmp_.internal_comparator is not initialized in this constructor nor in any functions that it calls.

db/version_edit.h:
145  FdWithKeyRange()
146      : fd(),
147        smallest_key(),
148        largest_key() {

CID 1418254 (#1 of 1): Uninitialized pointer field (UNINIT_CTOR)
2. uninit_member: Non-static class member file_metadata is not initialized in this constructor nor in any functions that it calls.
149  }

db/version_set.cc:
120    }

CID 1322789 (#1 of 1): Uninitialized pointer field (UNINIT_CTOR)
4. uninit_member: Non-static class member curr_file_level_ is not initialized in this constructor nor in any functions that it calls.
121  }

db/write_batch.cc:
 939    assert(cf_mems_);

CID 1419862 (#1 of 1): Uninitialized scalar field (UNINIT_CTOR)
3. uninit_member: Non-static class member rebuilding_trx_seq_ is not initialized in this constructor nor in any functions that it calls.
 940  }
Closes https://github.com/facebook/rocksdb/pull/3092

Differential Revision: D6505666

Pulled By: yiwu-arbug

fbshipit-source-id: fd2c68948a0280772691a419d72ac7e190951d86

db/version_builder.cc

@@ -66,6 +66,8 @@ class VersionBuilder::Rep {
     enum SortMethod { kLevel0 = 0, kLevelNon0 = 1, } sort_method;
     const InternalKeyComparator* internal_comparator;
 
+    FileComparator() : internal_comparator(nullptr) {}
+
     bool operator()(FileMetaData* f1, FileMetaData* f2) const {
       switch (sort_method) {
         case kLevel0:

db/version_edit.h

@@ -144,6 +144,7 @@ struct FdWithKeyRange {
 
   FdWithKeyRange()
       : fd(),
+        file_metadata(nullptr),
         smallest_key(),
         largest_key() {
   }

db/version_set.cc

@@ -102,6 +102,7 @@ class FilePicker {
 #endif
         level_files_brief_(file_levels),
         is_hit_file_last_in_level_(false),
+        curr_file_level_(nullptr),
         user_key_(user_key),
         ikey_(ikey),
         file_indexer_(file_indexer),
@@ -2402,6 +2403,7 @@ VersionSet::VersionSet(const std::string& dbname,
       db_options_(db_options),
       next_file_number_(2),
       manifest_file_number_(0),  // Filled by Recover()
+      options_file_number_(0),
       pending_manifest_file_number_(0),
       last_sequence_(0),
       last_allocated_sequence_(0),

db/write_batch.cc

@@ -968,6 +968,7 @@ class MemTableInserter : public WriteBatch::Handler {
         post_info_created_(false),
         has_valid_writes_(has_valid_writes),
         rebuilding_trx_(nullptr),
+        rebuilding_trx_seq_(0),
         seq_per_batch_(seq_per_batch),
         // Write after commit currently uses one seq per key (instead of per
         // batch). So seq_per_batch being false indicates write_after_commit