address code review comments on 5e3aeb5f8e

- reduce string copying in Compaction::Summary
- simplify file number checking in UniversalCompactionStopStyleSimilarSize unit test

db/compaction.cc

@@ -194,7 +194,7 @@ static void FileSizeSummary(unsigned long long sz, char* output, int len) {
   }
 }
 
-static void InputSummary(std::vector<FileMetaData*>& files, char* output,
+static int InputSummary(std::vector<FileMetaData*>& files, char* output,
                          int len) {
   int write = 0;
   for (unsigned int i = 0; i < files.size(); i++) {
@@ -209,29 +209,37 @@ static void InputSummary(std::vector<FileMetaData*>& files, char* output,
       break;
     write += ret;
   }
+  return write;
 }
 
 void Compaction::Summary(char* output, int len) {
   int write = snprintf(output, len,
-      "Base version %lu Base level %d, seek compaction:%d, inputs:",
+      "Base version %lu Base level %d, seek compaction:%d, inputs: [",
       (unsigned long)input_version_->GetVersionNumber(),
       level_,
       seek_compaction_);
-  if (write < 0 || write > len) {
+  if (write < 0 || write >= len) {
+    return;
+  }
+
+  write += InputSummary(inputs_[0], output+write, len-write);
+  if (write < 0 || write >= len) {
+    return;
+  }
+
+  write += snprintf(output+write, len-write, "],[");
+  if (write < 0 || write >= len) {
     return;
   }
 
-  char level_low_summary[1024];
-  InputSummary(inputs_[0], level_low_summary, sizeof(level_low_summary));
-  char level_up_summary[1024];
   if (inputs_[1].size()) {
-    InputSummary(inputs_[1], level_up_summary, sizeof(level_up_summary));
-  } else {
-    level_up_summary[0] = '\0';
+    write += InputSummary(inputs_[1], output+write, len-write);
+  }
+  if (write < 0 || write >= len) {
+    return;
   }
 
-  snprintf(output + write, len - write, "[%s],[%s]",
-      level_low_summary, level_up_summary);
+  snprintf(output+write, len-write, "]");
 }
 
 }  // namespace rocksdb

db/db_test.cc

@@ -2051,6 +2051,7 @@ TEST(DBTest, UniversalCompactionStopStyleSimilarSize) {
   options.level0_file_num_compaction_trigger = 4;
   options.compaction_options_universal.size_ratio = 10;
   options.compaction_options_universal.stop_style = kCompactionStopStyleSimilarSize;
+  options.num_levels=1;
   Reopen(&options);
 
   Random rnd(301);
@@ -2082,9 +2083,6 @@ TEST(DBTest, UniversalCompactionStopStyleSimilarSize) {
   // (level0_file_num_compaction_trigger+1)=4 files and should have a big
   // file of size 4.
   ASSERT_EQ(NumTableFilesAtLevel(0), 1);
-  for (int i = 1; i < options.num_levels ; i++) {
-    ASSERT_EQ(NumTableFilesAtLevel(i), 0);
-  }
 
   // Stage 2:
   //   Now we have one file at level 0, with size 4. We also have some data in
@@ -2116,10 +2114,6 @@ TEST(DBTest, UniversalCompactionStopStyleSimilarSize) {
   // Before compaction, we have 4 files at level 0, with size 4, 0.4, 1, 1.
   // After compaction, we should have 3 files, with size 4, 0.4, 2.
   ASSERT_EQ(NumTableFilesAtLevel(0), 3);
-  for (int i = 1; i < options.num_levels ; i++) {
-    ASSERT_EQ(NumTableFilesAtLevel(i), 0);
-  }
-
   // Stage 3:
   //   Now we have 3 files at level 0, with size 4, 0.4, 2. Generate one
   //   more file at level-0, which should trigger level-0 compaction.
@@ -2130,9 +2124,6 @@ TEST(DBTest, UniversalCompactionStopStyleSimilarSize) {
   dbfull()->TEST_WaitForCompact();
   // Level-0 compaction is triggered, but no file will be picked up.
   ASSERT_EQ(NumTableFilesAtLevel(0), 4);
-  for (int i = 1; i < options.num_levels ; i++) {
-    ASSERT_EQ(NumTableFilesAtLevel(i), 0);
-  }
 }
 
 #if defined(SNAPPY) && defined(ZLIB) && defined(BZIP2)