Use pre-increment instead of post-increment for iterators (#5296)

Summary:
Google C++ style guide indicates pre-increment should be used for iterators: https://google.github.io/styleguide/cppguide.html#Preincrement_and_Predecrement. Replaced all instances of ' it++' by ' ++it' (where type is iterator). So this covers the cases where iterators are named 'it'.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5296

Differential Revision: D15301256

Pulled By: tfersch

fbshipit-source-id: 2803483c1392504ad3b281d21db615429c71114b

db/compaction_job.cc

@@ -519,7 +519,7 @@ void CompactionJob::GenSubcompactionBoundaries() {
   auto* v = compact_->compaction->input_version();
   for (auto it = bounds.begin();;) {
     const Slice a = *it;
-    it++;
+    ++it;
 
     if (it == bounds.end()) {
       break;

db/db_impl.h

@@ -725,7 +725,7 @@ class DBImpl : public DB {
 
   void DeleteAllRecoveredTransactions() {
     for (auto it = recovered_transactions_.begin();
-         it != recovered_transactions_.end(); it++) {
+         it != recovered_transactions_.end(); ++it) {
       delete it->second;
     }
     recovered_transactions_.clear();

db/db_impl_compaction_flush.cc

@@ -2794,7 +2794,7 @@ void DBImpl::RemoveManualCompaction(DBImpl::ManualCompactionState* m) {
       it = manual_compaction_dequeue_.erase(it);
       return;
     }
-    it++;
+    ++it;
   }
   assert(false);
   return;
@@ -2815,7 +2815,7 @@ bool DBImpl::ShouldntRunManualCompaction(ManualCompactionState* m) {
   bool seen = false;
   while (it != manual_compaction_dequeue_.end()) {
     if (m == (*it)) {
-      it++;
+      ++it;
       seen = true;
       continue;
     } else if (MCOverlap(m, (*it)) && (!seen && !(*it)->in_progress)) {
@@ -2824,7 +2824,7 @@ bool DBImpl::ShouldntRunManualCompaction(ManualCompactionState* m) {
       // and (*it) is ahead in the queue and is not yet in progress
       return true;
     }
-    it++;
+    ++it;
   }
   return false;
 }
@@ -2842,7 +2842,7 @@ bool DBImpl::HaveManualCompaction(ColumnFamilyData* cfd) {
       // in progress
       return true;
     }
-    it++;
+    ++it;
   }
   return false;
 }
@@ -2855,7 +2855,7 @@ bool DBImpl::HasExclusiveManualCompaction() {
     if ((*it)->exclusive) {
       return true;
     }
-    it++;
+    ++it;
   }
   return false;
 }

db/memtable_list.cc

@@ -437,7 +437,7 @@ Status MemTableList::TryInstallMemtableFlushResults(
           ++mem_id;
         }
       } else {
-        for (auto it = current_->memlist_.rbegin(); batch_count-- > 0; it++) {
+        for (auto it = current_->memlist_.rbegin(); batch_count-- > 0; ++it) {
           MemTable* m = *it;
           // commit failed. setup state so that we can flush again.
           ROCKS_LOG_BUFFER(log_buffer, "Level-0 commit table #%" PRIu64

db/prefix_test.cc

@@ -751,7 +751,7 @@ TEST_F(PrefixTest, PrefixSeekModePrev) {
       for (size_t k = 0; k < 9; k++) {
         if (rnd.OneIn(2) || it == whole_map.begin()) {
           iter->Next();
-          it++;
+          ++it;
           if (FLAGS_enable_print) {
             std::cout << "Next >> ";
           }

utilities/transactions/pessimistic_transaction_db.cc

@@ -121,7 +121,7 @@ Status PessimisticTransactionDB::Initialize(
   assert(dbimpl != nullptr);
   auto rtrxs = dbimpl->recovered_transactions();
 
-  for (auto it = rtrxs.begin(); it != rtrxs.end(); it++) {
+  for (auto it = rtrxs.begin(); it != rtrxs.end(); ++it) {
     auto recovered_trx = it->second;
     assert(recovered_trx);
     assert(recovered_trx->batches_.size() == 1);
@@ -594,7 +594,7 @@ void PessimisticTransactionDB::GetAllPreparedTransactions(
   assert(transv);
   transv->clear();
   std::lock_guard<std::mutex> lock(name_map_mutex_);
-  for (auto it = transactions_.begin(); it != transactions_.end(); it++) {
+  for (auto it = transactions_.begin(); it != transactions_.end(); ++it) {
     if (it->second->GetState() == Transaction::PREPARED) {
       transv->push_back(it->second);
     }

utilities/transactions/transaction_test.cc

@@ -567,7 +567,7 @@ TEST_P(TransactionTest, DeadlockCycleShared) {
     TransactionID leaf_id =
         dlock_entry[dlock_entry.size() - 1].m_txn_id - offset_root;
 
-    for (auto it = dlock_entry.rbegin(); it != dlock_entry.rend(); it++) {
+    for (auto it = dlock_entry.rbegin(); it != dlock_entry.rend(); ++it) {
       auto dl_node = *it;
       ASSERT_EQ(dl_node.m_txn_id, offset_root + leaf_id);
       ASSERT_EQ(dl_node.m_cf_id, 0);
@@ -774,7 +774,7 @@ TEST_P(TransactionStressTest, DeadlockCycle) {
     }
 
     // Iterates backwards over path verifying decreasing txn_ids.
-    for (auto it = dlock_entry.rbegin(); it != dlock_entry.rend(); it++) {
+    for (auto it = dlock_entry.rbegin(); it != dlock_entry.rend(); ++it) {
       auto dl_node = *it;
       ASSERT_EQ(dl_node.m_txn_id, len + curr_txn_id - 1);
       ASSERT_EQ(dl_node.m_cf_id, 0);

utilities/transactions/write_prepared_transaction_test.cc

@@ -1099,7 +1099,7 @@ TEST_P(SnapshotConcurrentAccessTest, SnapshotConcurrentAccessTest) {
           new_snapshots.push_back(snapshots[old_snapshots.size() + i]);
         }
         for (auto it = common_snapshots.begin(); it != common_snapshots.end();
-             it++) {
+             ++it) {
           auto snapshot = *it;
           // Create a commit entry that is around the snapshot and thus should
           // be not be discarded
@@ -1166,12 +1166,12 @@ TEST_P(WritePreparedTransactionTest, AdvanceMaxEvictedSeqBasicTest) {
   // b. delayed prepared should contain every txn <= max and prepared should
   // only contain txns > max
   auto it = initial_prepared.begin();
-  for (; it != initial_prepared.end() && *it <= new_max; it++) {
+  for (; it != initial_prepared.end() && *it <= new_max; ++it) {
     ASSERT_EQ(1, wp_db->delayed_prepared_.erase(*it));
   }
   ASSERT_TRUE(wp_db->delayed_prepared_.empty());
   for (; it != initial_prepared.end() && !wp_db->prepared_txns_.empty();
-       it++, wp_db->prepared_txns_.pop()) {
+       ++it, wp_db->prepared_txns_.pop()) {
     ASSERT_EQ(*it, wp_db->prepared_txns_.top());
   }
   ASSERT_TRUE(it == initial_prepared.end());

utilities/transactions/write_prepared_txn_db.cc

@@ -798,7 +798,7 @@ void WritePreparedTxnDB::UpdateSnapshots(
   // afterwards.
   size_t i = 0;
   auto it = snapshots.begin();
-  for (; it != snapshots.end() && i < SNAPSHOT_CACHE_SIZE; it++, i++) {
+  for (; it != snapshots.end() && i < SNAPSHOT_CACHE_SIZE; ++it, ++i) {
     snapshot_cache_[i].store(*it, std::memory_order_release);
     TEST_IDX_SYNC_POINT("WritePreparedTxnDB::UpdateSnapshots:p:", ++sync_i);
     TEST_IDX_SYNC_POINT("WritePreparedTxnDB::UpdateSnapshots:s:", sync_i);
@@ -812,7 +812,7 @@ void WritePreparedTxnDB::UpdateSnapshots(
   }
 #endif
   snapshots_.clear();
-  for (; it != snapshots.end(); it++) {
+  for (; it != snapshots.end(); ++it) {
     // Insert them to a vector that is less efficient to access
     // concurrently
     snapshots_.push_back(*it);

utilities/transactions/write_unprepared_txn_db.cc

@@ -46,7 +46,7 @@ Status WriteUnpreparedTxnDB::RollbackRecoveredTransaction(
   };
 
   // Iterate starting with largest sequence number.
-  for (auto it = rtxn->batches_.rbegin(); it != rtxn->batches_.rend(); it++) {
+  for (auto it = rtxn->batches_.rbegin(); it != rtxn->batches_.rend(); ++it) {
     auto last_visible_txn = it->first - 1;
     const auto& batch = it->second.batch_;
     WriteBatch rollback_batch;