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TAJO-2059: Binary search in BST reader does compare too frequently #945

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TAJO-2059: Binary search in BST reader does compare too frequently #945

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d5fdf2f
lightweight improvement
eminency Jan 13, 2016
a7b2686
Refine binary search
eminency Jan 13, 2016
58a59e8
test code
eminency Jan 15, 2016
74c857d
Revert "test code"
eminency Jan 15, 2016
c5e2a57
Fix for one item array
eminency Jan 17, 2016
4b26bfc
Handles when size of array is 1
eminency Jan 20, 2016
282e4b6
Remove unused imports
eminency Jan 20, 2016
0c51ddc
Use bit operation
eminency Feb 24, 2016
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81 changes: 59 additions & 22 deletions tajo-storage/tajo-storage-hdfs/src/main/java/org/apache/tajo/storage/index/bst/BSTIndex.java
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Original file line number Diff line number Diff line change
Expand Up @@ -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) {
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@jihoonson jihoonson Feb 15, 2016

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In this method binarySearch(), endPos is intended as an exclusive end position. It looks that codes in this block need to consider this intention.

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) >>> 1;
}
}
return offset;
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