some comment change

db/db_impl/db_impl.h

@@ -1515,9 +1515,9 @@ class DBImpl : public DB {
   // REQUIRES: this thread is currently at the front of the main writer queue.
   // @param prep_log refers to the WAL that contains prepare record
   // for the transaction based on wbwi.
-  // @param assigned_seqno Sequence number for the ingested memtable.
-  // @param the value of versions_->LastSequence() after the write ingests
-  // `wbwi` is done.
+  // @param assigned_seqno Sequence numbers for the ingested memtable.
+  // @param last_seqno the value of versions_->LastSequence() after the write
+  // ingests `wbwi` is done.
   Status IngestWBWI(std::shared_ptr<WriteBatchWithIndex> wbwi,
                     const WBWIMemTable::SeqnoRange& assigned_seqno,
                     uint64_t min_prep_log, SequenceNumber last_seqno);

db/db_impl/db_impl_write.cc

@@ -600,7 +600,8 @@ Status DBImpl::WriteImpl(const WriteOptions& write_options,
     // the seq per valid written key to mem.
     size_t seq_inc = seq_per_batch_ ? valid_batches : total_count;
     if (wbwi) {
-      // Reserve sequence numbers for recovery. During recovery,
+      // Reserve sequence numbers for the ingested memtable. We need to reserve
+      // at lease this amount for recovery. During recovery,
       // transactions do not commit by ingesting WBWI. The sequence number
       // associated with the commit entry in WAL is used as the starting
       // sequence number for inserting into memtable. We need to reserve

db/memtable_list.cc

@@ -447,6 +447,7 @@ void MemTableList::PickMemtablesToFlush(uint64_t max_memtable_id,
     }
   }
   if (!ret->empty() && it != memlist.rend()) {
+    // checks that the first memtable not picked to flush is not ingested wbwi.
     // Ingested memtable should be flushed together with the memtable before it
     // since they map to the same WAL and have the same NextLogNumber().
     assert(strcmp((*it)->Name(), "WBWIMemTable") != 0);

include/rocksdb/utilities/transaction_db.h

@@ -346,8 +346,9 @@ struct TransactionOptions {
   // makes Commit() much faster for transactions with many operations.
   //
   // Note that the transaction will be ingested as an immutable memtable for
-  // each CF it updates. So ingesting many transactions in a short period of
-  // time may cause stall due to too many memtables.
+  // CFs it updates, and the current memtable will be switched to a new one.
+  // So ingesting many transactions in a short period of time may cause stall
+  // due to too many memtables.
   bool commit_bypass_memtable = false;
 };
 

include/rocksdb/utilities/write_batch_with_index.h

@@ -358,7 +358,7 @@ class WriteBatchWithIndex : public WriteBatchBase {
     uint32_t entry_count = 0;
     uint32_t overwritten_sd_count = 0;
   };
-  // Will track CF ID, per CF entry count and overwritten sd count writes.
+  // Will track CF ID, per CF entry count and overwritten sd count.
   // Should be enabled when WBWI is empty for correct tracking.
   void SetTrackPerCFStat(bool track);
   const std::unordered_map<uint32_t, CFStat>& GetCFStats() const;

memtable/wbwi_memtable.h

@@ -25,7 +25,6 @@ namespace ROCKSDB_NAMESPACE {
 // - live memtable contains SD(k)
 // - flush memtable and compact with L0 will drop SD(k) and PUT(k)
 // - the PUT(k) in L1 incorrectly becomes visible
-//
 // So during flush, iterator from this memtable will need emit overwritten
 // single deletion. These single deletion entries will be
 // assigned seqno.upper_bound - 1.

utilities/write_batch_with_index/write_batch_with_index.cc

@@ -123,7 +123,6 @@ bool WriteBatchWithIndex::Rep::UpdateExistingEntryWithCfId(
   if (track_cf_stat) {
     if (non_const_entry->has_single_del &&
         !non_const_entry->has_overwritten_single_del) {
-      // increment count here
       cf_id_to_stat[column_family_id].overwritten_sd_count++;
       non_const_entry->has_overwritten_single_del = true;
     }