Hitesh Khamesra created ARROW-5057:
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Summary: Java: allocate new buffer code doesn't release extra
allocated buffer properly
Key: ARROW-5057
URL: https://issues.apache.org/jira/browse/ARROW-5057
Project: Apache Arrow
Issue Type: Bug
Components: Java
Affects Versions: 0.12.1
Reporter: Hitesh Khamesra
[Class
BaseValueVector|https://github.com/apache/arrow/blob/master/java/vector/src/main/java/org/apache/arrow/vector/BaseValueVector.java]
's method allocFixedDataAndValidityBufs on line#162 allocates a buffer in
power of 2 size. After that, it has a code release extra buffer. For that, it
calculates the extra buffer from allocated size "bufferSize" but in my opinion,
it should take original "valueCount" to find the extra buffer size.
Here, I see a problem in line#162, where its taking "bufferSize" to find the
extra allocated bytes. It should be "valueCount*typeWidth + valueCount/8".
Here is an example for that. Let's take 1000 ints. Then,
valueCount = 1000 ints
typWidth = 4 bytes
validitiyBufferSize = 125 bytes
valueBufferSize = 4000 bytes
combinedSize(valueBufferSize + validityBufferSize) = 4128 bytes (multiple of 8)
combinedSizeWith2ThePowerSize = 8192 bytes, this will be "bufferSize" at
line#152.
With the above calculation, this code should release
(combinedSizeWith2ThePowerSize - combinedSize) = 4064 bytes. But, this is not
happening.
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