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Lock the random access if a forward or backward seek is detected #1250

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Lock the random access if a forward or backward seek is detected #1250

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19 changes: 10 additions & 9 deletions gcsio/src/main/java/com/google/cloud/hadoop/gcsio/FileAccessPatternManager.java
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Original file line number Diff line number Diff line change
Expand Up @@ -65,12 +65,10 @@ public void updateAccessPattern(long currentPosition) {
return;
}
if (readOptions.getFadvise() == Fadvise.AUTO_RANDOM) {
if (randomAccess) {
if (isBackwardOrForwardSeekNotRequested()) {
if (isSequentialAccessPattern(currentPosition)) {
unsetRandomAccess();
}
} else {
if (isRandomAccessPattern(currentPosition)) {
} else if (isRandomAccessPattern(currentPosition)) {
setRandomAccess();
}
}
Expand Down Expand Up @@ -151,18 +149,21 @@ private boolean isRandomAccessPattern(long currentPosition) {
return false;
}

private boolean isBackwardOrForwardSeekNotRequested() {
return !isBackwardSeekRequested && !isForwardSeekRequested;
}

private boolean shouldDetectSequentialAccess() {
return randomAccess
&& !isBackwardSeekRequested
&& !isForwardSeekRequested
&& isBackwardOrForwardSeekNotRequested()
&& consecutiveSequentialCount >= readOptions.getFadviseRequestTrackCount()
&& readOptions.getFadvise() == Fadvise.AUTO_RANDOM;
}

private boolean shouldDetectRandomAccess() {
return !randomAccess
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If already in randomAccess mode there is no need to detect random access.

I do agree that the current logic will not update backwardSeek and forwardSeek if occurredwhen random access was set but I would suggest updating those flags well within fn:updateAccessPattern .

&& (readOptions.getFadvise() == Fadvise.AUTO
|| readOptions.getFadvise() == Fadvise.AUTO_RANDOM);
return (!randomAccess && readOptions.getFadvise() == Fadvise.AUTO)
|| (isBackwardOrForwardSeekNotRequested()
&& readOptions.getFadvise() == Fadvise.AUTO_RANDOM);
}

private void setRandomAccess() {
Expand Down
23 changes: 23 additions & 0 deletions gcsio/src/test/java/com/google/cloud/hadoop/gcsio/FileAccessPatternManagerTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -169,5 +169,28 @@ public void testAutoRandomMode() {
assertThat(fileAccessPattern.isRandomAccessPattern()).isEqualTo(expectedRandomAccess[i]);
fileAccessPattern.updateLastServedIndex(currentPosition);
}

// R --> R backward seek
// a backward seek should lock the random pattern
readIndexes = new long[] {4, 1, 2, 3, 4, 5, 0, 1, 2, 3, 4};
expectedRandomAccess =
new boolean[] {true, true, true, true, true, true, true, true, true, true, true};
for (int i = 0; i < readIndexes.length; i++) {
long currentPosition = readIndexes[i];
fileAccessPattern.updateAccessPattern(currentPosition);
assertThat(fileAccessPattern.isRandomAccessPattern()).isEqualTo(expectedRandomAccess[i]);
fileAccessPattern.updateLastServedIndex(currentPosition);
}

// R --> R forward seek
// a forward seek should lock the random pattern
readIndexes = new long[] {0, 11, 12, 13, 14, 15};
expectedRandomAccess = new boolean[] {true, true, true, true, true, true};
for (int i = 0; i < readIndexes.length; i++) {
long currentPosition = readIndexes[i];
fileAccessPattern.updateAccessPattern(currentPosition);
assertThat(fileAccessPattern.isRandomAccessPattern()).isEqualTo(expectedRandomAccess[i]);
fileAccessPattern.updateLastServedIndex(currentPosition);
}
}
}