Ensure ColumnFamilyOptions.num_levels >= 2 when level compaction is used.

Summary: Ensure ColumnFamilyOptions.num_levels >= 2 when level compaction is used.

Test Plan: Extend SanitizeOptions test in column_family_test

Reviewers: sdong, rven, anthony, krishnanm86, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D38829

db/column_family.cc

@@ -136,6 +136,13 @@ ColumnFamilyOptions SanitizeOptions(const DBOptions& db_options,
   result.min_write_buffer_number_to_merge =
       std::min(result.min_write_buffer_number_to_merge,
                result.max_write_buffer_number - 1);
+  if (result.num_levels < 1) {
+    result.num_levels = 1;
+  }
+  if (result.compaction_style == kCompactionStyleLevel &&
+      result.num_levels < 2) {
+    result.num_levels = 2;
+  }
   if (result.max_mem_compaction_level >= result.num_levels) {
     result.max_mem_compaction_level = result.num_levels - 1;
   }

db/column_family_test.cc

@@ -1029,10 +1029,14 @@ TEST_F(ColumnFamilyTest, CreateMissingColumnFamilies) {
 
 TEST_F(ColumnFamilyTest, SanitizeOptions) {
   DBOptions db_options;
+  for (int s = kCompactionStyleLevel; s <= kCompactionStyleUniversal; ++s) {
+    for (int l = 0; l <= 2; l++) {
       for (int i = 1; i <= 3; i++) {
         for (int j = 1; j <= 3; j++) {
           for (int k = 1; k <= 3; k++) {
             ColumnFamilyOptions original;
+            original.compaction_style = static_cast<CompactionStyle>(s);
+            original.num_levels = l;
             original.level0_stop_writes_trigger = i;
             original.level0_slowdown_writes_trigger = j;
             original.level0_file_num_compaction_trigger = k;
@@ -1044,6 +1048,16 @@ TEST_F(ColumnFamilyTest, SanitizeOptions) {
                         result.level0_file_num_compaction_trigger);
             ASSERT_TRUE(result.level0_file_num_compaction_trigger ==
                         original.level0_file_num_compaction_trigger);
+            if (s == kCompactionStyleLevel) {
+              ASSERT_GE(result.num_levels, 2);
+            } else {
+              ASSERT_GE(result.num_levels, 1);
+              if (original.num_levels >= 1) {
+                ASSERT_EQ(result.num_levels, original.num_levels);
+              }
+            }
+          }
+        }
       }
     }
   }