re-enable BlockBasedTable::SetupForCompaction()

Summary:
It was commented out in D22545 by accident. Keep the option in
ImmutableOptions for now. I can make it dynamic in
https://reviews.facebook.net/D23349

Test Plan: make release

Reviewers: sdong, yhchiang, igor

Reviewed By: igor

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D23865

include/rocksdb/immutable_options.h

@@ -77,6 +77,8 @@ struct ImmutableCFOptions {
   std::vector<CompressionType> compression_per_level;
 
   CompressionOptions compression_opts;
+
+  Options::AccessHint access_hint_on_compaction_start;
 };
 
 }  // namespace rocksdb

include/rocksdb/options.h

@@ -58,6 +58,7 @@ enum CompactionStyle : char {
   kCompactionStyleFIFO = 0x2,       // FIFO compaction style
 };
 
+
 struct CompactionOptionsFIFO {
   // once the total sum of table files reaches this, we will delete the oldest
   // table file
@@ -783,12 +784,13 @@ struct DBOptions {
   // Specify the file access pattern once a compaction is started.
   // It will be applied to all input files of a compaction.
   // Default: NORMAL
-  enum {
-    NONE,
-    NORMAL,
-    SEQUENTIAL,
-    WILLNEED
-  } access_hint_on_compaction_start;
+  enum AccessHint {
+      NONE,
+      NORMAL,
+      SEQUENTIAL,
+      WILLNEED
+  };
+  AccessHint access_hint_on_compaction_start;
 
   // Use adaptive mutex, which spins in the user space before resorting
   // to kernel. This could reduce context switch when the mutex is not

table/block_based_table_reader.cc

@@ -532,8 +532,7 @@ Status BlockBasedTable::Open(const ImmutableCFOptions& ioptions,
 }
 
 void BlockBasedTable::SetupForCompaction() {
-  /*
-  switch (.access_hint_on_compaction_start) {
+  switch (rep_->ioptions.access_hint_on_compaction_start) {
     case Options::NONE:
       break;
     case Options::NORMAL:
@@ -549,7 +548,6 @@ void BlockBasedTable::SetupForCompaction() {
       assert(false);
   }
   compaction_optimized_ = true;
-  */
 }
 
 std::shared_ptr<const TableProperties> BlockBasedTable::GetTableProperties()

util/options.cc

@@ -59,7 +59,8 @@ ImmutableCFOptions::ImmutableCFOptions(const Options& options)
     use_fsync(options.use_fsync),
     compression(options.compression),
     compression_per_level(options.compression_per_level),
-    compression_opts(options.compression_opts) {}
+    compression_opts(options.compression_opts),
+    access_hint_on_compaction_start(options.access_hint_on_compaction_start) {}
 
 ColumnFamilyOptions::ColumnFamilyOptions()
     : comparator(BytewiseComparator()),