[GitHub] tajo pull request: TAJO-2059: Binary search in BST reader does com...

[jihoonson <gi...@git.apache.org>]

Github user jihoonson commented on a diff in the pull request:

    https://github.com/apache/tajo/pull/945#discussion_r52862691
  
    --- Diff: tajo-storage/tajo-storage-hdfs/src/main/java/org/apache/tajo/storage/index/bst/BSTIndex.java ---
    @@ -794,42 +794,79 @@ private int binarySearch(Tuple[] arr, Tuple key, int startPos, int endPos) {
           int offset = -1;
           int start = startPos;
           int end = endPos;
    +      int prevCenter = -1;
     
           //http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6412541
           int centerPos = (start + end) >>> 1;
           if (arr.length == 0) {
             LOG.error("arr.length: 0, loadNum: " + loadNum + ", inited: " + inited.get());
    +        return -1;
           }
    +
    +      correctable = false;
    +      if (arr.length == 1) {
    +        int comp = comparator.compare(arr[0], key);
    +
    +        if (comp < 0) {
    +          return 0;
    +        } else if (comp > 0) {
    +          return -1;
    +        }
    +
    +        correctable = true;
    +        return 0;
    +      }
    +
           while (true) {
    -        if (comparator.compare(arr[centerPos], key) > 0) {
    -          if (centerPos == 0) {
    -            correctable = false;
    -            break;
    -          } else if (comparator.compare(arr[centerPos - 1], key) < 0) {
    -            correctable = false;
    -            offset = centerPos - 1;
    +        if (end - start == 1) {
    +          int comp;
    +          // prevCenter should be either end or start
    +          if (end == prevCenter) {
    +            comp = comparator.compare(arr[start], key);
    +
    +            if (comp == 0) {
    +              correctable = true;
    +              offset = start;
    +            } else if (comp < 0) {
    +              offset = start;
    +            }
                 break;
               } else {
    -            end = centerPos;
    -            centerPos = (start + end) / 2;
    -          }
    -        } else if (comparator.compare(arr[centerPos], key) < 0) {
    -          if (centerPos == arr.length - 1) {
    -            correctable = false;
    -            offset = centerPos;
    -            break;
    -          } else if (comparator.compare(arr[centerPos + 1], key) > 0) {
    -            correctable = false;
    -            offset = centerPos;
    +            if (end == arr.length) {
    +              if (comparator.compare(arr[start], key) == 0) {
    +                correctable = true;
    +              }
    +              offset = start;
    +              break;
    +            }
    +
    +            comp = comparator.compare(arr[end], key);
    +            if (comp == 0) {
    +              correctable = true;
    +              offset = end;
    +            } else if (comp > 0) {
    +              offset = start;
    +            }
                 break;
    -          } else {
    -            start = centerPos + 1;
    -            centerPos = (start + end) / 2;
               }
    -        } else {
    +        }
    +
    +        int compareResult = comparator.compare(arr[centerPos], key);
    +
    +        if (compareResult == 0) {
               correctable = true;
               offset = centerPos;
               break;
    +        } else {
    +          prevCenter = centerPos;
    +
    +          if (compareResult > 0) {
    +            end = centerPos;
    +          } else {
    +            start = centerPos;
    +          }
    +
    +          centerPos = (start + end) / 2;
    --- End diff --
    
    This line also looks to be changed to ```centerPos = (start + end) >>> 1;```


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