Fix sequence number bump logic in multi-CF SST ingestion (#9005)

Summary:
The code in `IngestExternalFiles()` that bumps the DB's sequence number
depending on what seqnos were assigned to the files has 3 bugs:

1) There is an assertion that the sequence number is increased in all the
affected column families, but this is unnecessary, it is fine if some files can
stick to a lower sequence number. It is very easy to hit the assertion: it is
sufficient to insert 2 files in 2 CFs, one which overlaps the CF and one that
doesn't (for example the CF is empty). The line added in the
`IngestFilesIntoMultipleColumnFamilies_Success` test makes the assertion fail.

2) SetLastSequence() is called with the sum of all the bumps across CFs, but we
should take the maximum instead, as all CFs start with the current seqno and bump
it independently.

3) The code above is accidentally under a `#ifndef NDEBUG`, so it doesn't run in
optimized builds, so some files may be assigned seqnos from the future.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9005

Test Plan:
Added line in `IngestFilesIntoMultipleColumnFamilies_Success` that
triggers the assertion, verified that the test (and all the others) pass after
the fix.

Reviewed By: ajkr

Differential Revision: D31597892

Pulled By: ot

fbshipit-source-id: c2d3237f90290df1178736ace8653a9623f5a770

HISTORY.md

@@ -1,4 +1,8 @@
 # Rocksdb Change Log
+## Unreleased
+### Bug Fixes
+* Fixed bug in calls to `IngestExternalFiles()` with files for multiple column families. The bug could have introduced a delay in ingested file keys becoming visible after `IngestExternalFiles()` returned. Furthermore, mutations to ingested file keys while they were invisible could have been dropped (not necessarily immediately).
+
 ## 6.25.2 (2021-10-11)
 ### Bug Fixes
 * Fix `DisableManualCompaction()` to cancel compactions even when they are waiting on automatic compactions to drain due to `CompactRangeOptions::exclusive_manual_compactions == true`.

db/db_impl/db_impl.cc

@@ -4679,14 +4679,11 @@ Status DBImpl::IngestExternalFiles(
     if (status.ok()) {
       int consumed_seqno_count =
           ingestion_jobs[0].ConsumedSequenceNumbersCount();
-#ifndef NDEBUG
       for (size_t i = 1; i != num_cfs; ++i) {
-        assert(!!consumed_seqno_count ==
-               !!ingestion_jobs[i].ConsumedSequenceNumbersCount());
-        consumed_seqno_count +=
-            ingestion_jobs[i].ConsumedSequenceNumbersCount();
+        consumed_seqno_count =
+            std::max(consumed_seqno_count,
+                     ingestion_jobs[i].ConsumedSequenceNumbersCount());
       }
-#endif
       if (consumed_seqno_count > 0) {
         const SequenceNumber last_seqno = versions_->LastSequence();
         versions_->SetLastAllocatedSequence(last_seqno + consumed_seqno_count);

db/external_sst_file_ingestion_job.h

@@ -139,7 +139,7 @@ class ExternalSstFileIngestionJob {
                              IngestedFileInfo* file_to_ingest,
                              SuperVersion* sv);
 
-  // Assign `file_to_ingest` the appropriate sequence number and  the lowest
+  // Assign `file_to_ingest` the appropriate sequence number and the lowest
   // possible level that it can be ingested to according to compaction_style.
   // REQUIRES: Mutex held
   Status AssignLevelAndSeqnoForIngestedFile(SuperVersion* sv,

db/external_sst_file_test.cc

@@ -2421,6 +2421,12 @@ TEST_P(ExternalSSTFileTest, IngestFilesIntoMultipleColumnFamilies_Success) {
   Options options = CurrentOptions();
   options.env = fault_injection_env.get();
   CreateAndReopenWithCF({"pikachu", "eevee"}, options);
+
+  // Exercise different situations in different column families: two are empty
+  // (so no new sequence number is needed), but at least one overlaps with the
+  // DB and needs to bump the sequence number.
+  ASSERT_OK(db_->Put(WriteOptions(), "foo1", "oldvalue"));
+
   std::vector<ColumnFamilyHandle*> column_families;
   column_families.push_back(handles_[0]);
   column_families.push_back(handles_[1]);