/**
* Picks a block with samplingRate probability Used in the first phase of up-front partitioning.
*
* @param filename
* @param samplingRate
*/
public void scanWithBlockSampling(String filename, double samplingRate, OutputStream out) {
initScan(blockSampleSize);
FileChannel ch = IOUtils.openFileChannel(filename);
try {
for (long position = 0; ; position += blockSampleSize) {
while (sampleSucceed(samplingRate) == false) {
position += blockSampleSize;
}
ch.position(position);
if ((nRead = ch.read(bb)) == -1) {
break;
}
byteArrayIdx = previous = 0;
if (position != 0) {
// skip the first tuple if not starting of file.
while (byteArrayIdx < nRead && byteArray[byteArrayIdx] != newLine) {
byteArrayIdx++;
}
previous = ++byteArrayIdx;
}
processByteBuffer(null, out);
bb.clear();
out.flush(); // It only helps get an exact profiling?
}
} catch (IOException e) {
e.printStackTrace();
}
IOUtils.closeFileChannel(ch);
firstPass = false;
}
/**
* Does a full scan over entire data. Used in second phase of up-front partitioning.
*
* @param filename
* @param writer
*/
public void scan(String filename, PartitionWriter writer) {
initScan(bufferSize);
long sStartTime = System.nanoTime(), temp1;
long readTime = 0, processTime = 0;
FileChannel ch = IOUtils.openFileChannel(filename);
int counter = 0;
try {
while (true) {
temp1 = System.nanoTime();
boolean allGood = ((nRead = ch.read(bb)) != -1);
readTime += System.nanoTime() - temp1;
if (!allGood) break;
if (nRead == 0) continue;
counter++;
byteArrayIdx = previous = 0;
temp1 = System.nanoTime();
processByteBuffer(writer, null);
processTime += System.nanoTime() - temp1;
long startTime = System.nanoTime();
if (previous < nRead) { // is there a broken line in the end?
brokenLine = BinaryUtils.getBytes(byteArray, previous, nRead - previous);
hasLeftover = true;
}
brokenTime += System.nanoTime() - startTime;
startTime = System.nanoTime();
bb.clear();
clearTime += System.nanoTime() - startTime;
}
} catch (IOException e) {
e.printStackTrace();
}
IOUtils.closeFileChannel(ch);
firstPass = false;
System.out.println("counter:" + counter);
System.out.println(
"SCAN: Total Time taken = " + (System.nanoTime() - sStartTime) / 1E9 + " sec");
System.out.println("Line count = " + lineCount);
System.out.println("Average line size = " + (double) totalLineSize / lineCount);
System.out.println("SCAN: Read into buffer time = " + readTime / 1E9);
System.out.println("SCAN: Process buffer time = " + processTime / 1E9);
System.out.println("SCAN: Array copy time = " + arrayCopyTime / 1E9);
System.out.println("SCAN: Get bucket ID time = " + bucketIdTime / 1E9);
System.out.println("SCAN: Broken line fix time = " + brokenTime / 1E9);
System.out.println("SCAN: Buffer clear time = " + clearTime / 1E9);
}
