Make compaction_pri = kMinOverlappingRatio to be default (#4911)

Summary:
compaction_pri = kMinOverlappingRatio usually provides much better write amplification than the default.
https://github.com/facebook/rocksdb/pull/4907 fixes one shortcome of this option. Make it default.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4911

Differential Revision: D13789262

Pulled By: siying

fbshipit-source-id: d90acf8c4dede44f00d183ca4c7a210259378269

HISTORY.md

@@ -23,6 +23,9 @@
 * Fix incorrect `NotFound` point lookup result when querying the endpoint of a file that has been extended by a range tombstone.
 * Fix with pipelined write, write leaders's callback failure lead to the whole write group fail.
 
+### Change Default Options
+* Change options.compaction_pri's default to kMinOverlappingRatio
+
 ## 5.18.0 (11/30/2018)
 ### New Features
 * Introduced `JemallocNodumpAllocator` memory allocator. When being use, block cache will be excluded from core dump.

db/compaction_picker_test.cc

@@ -59,6 +59,9 @@ class CompactionPickerTest : public testing::Test {
         log_buffer_(InfoLogLevel::INFO_LEVEL, &logger_),
         file_num_(1),
         vstorage_(nullptr) {
+    // ioptions_.compaction_pri = kMinOverlappingRatio has its own set of
+    // tests to cover.
+    ioptions_.compaction_pri = kByCompensatedSize;
     fifo_options_.max_table_files_size = 1;
     mutable_cf_options_.RefreshDerivedOptions(ioptions_);
     ioptions_.cf_paths.emplace_back("dummy",

include/rocksdb/advanced_options.h

@@ -528,8 +528,8 @@ struct AdvancedColumnFamilyOptions {
 
   // If level compaction_style = kCompactionStyleLevel, for each level,
   // which files are prioritized to be picked to compact.
-  // Default: kByCompensatedSize
-  CompactionPri compaction_pri = kByCompensatedSize;
+  // Default: kMinOverlappingRatio
+  CompactionPri compaction_pri = kMinOverlappingRatio;
 
   // The options needed to support Universal Style compactions
   //

options/options.cc

@@ -439,6 +439,10 @@ DBOptions* DBOptions::OldDefaults(int rocksdb_major_version,
 
 ColumnFamilyOptions* ColumnFamilyOptions::OldDefaults(
     int rocksdb_major_version, int rocksdb_minor_version) {
+  if (rocksdb_major_version < 5 ||
+      (rocksdb_major_version == 5 && rocksdb_minor_version <= 18)) {
+    compaction_pri = CompactionPri::kByCompensatedSize;
+  }
   if (rocksdb_major_version < 4 ||
       (rocksdb_major_version == 4 && rocksdb_minor_version < 7)) {
     write_buffer_size = 4 << 20;
@@ -452,7 +456,6 @@ ColumnFamilyOptions* ColumnFamilyOptions::OldDefaults(
   } else if (rocksdb_major_version == 5 && rocksdb_minor_version < 2) {
     level0_stop_writes_trigger = 30;
   }
-  compaction_pri = CompactionPri::kByCompensatedSize;
 
   return this;
 }

options/options_test.cc

@@ -1528,6 +1528,7 @@ TEST_F(OptionsParserTest, DifferentDefault) {
   const std::string kOptionsFileName = "test-persisted-options.ini";
 
   ColumnFamilyOptions cf_level_opts;
+  ASSERT_EQ(CompactionPri::kMinOverlappingRatio, cf_level_opts.compaction_pri);
   cf_level_opts.OptimizeLevelStyleCompaction();
 
   ColumnFamilyOptions cf_univ_opts;
@@ -1597,6 +1598,14 @@ TEST_F(OptionsParserTest, DifferentDefault) {
     Options old_default_opts;
     old_default_opts.OldDefaults(5, 2);
     ASSERT_EQ(16 * 1024U * 1024U, old_default_opts.delayed_write_rate);
+    ASSERT_TRUE(old_default_opts.compaction_pri ==
+                CompactionPri::kByCompensatedSize);
+  }
+  {
+    Options old_default_opts;
+    old_default_opts.OldDefaults(5, 18);
+    ASSERT_TRUE(old_default_opts.compaction_pri ==
+                CompactionPri::kByCompensatedSize);
   }
 
   Options small_opts;