@leventov I removed synchronized from read operation, and it worked fine.
because there is only add operation to map and list, no delete operation, so
IndexOutOfBoundsException is unlikely happen.
>From the other side, current synchronized/rw lock can't actually do what it
>means. like:
1. threadA getMinValue(), threadB add(), threadA now holds the outdated
minValue.
As you can see, the lock behavior doesn't help in overall perspective.
to remove synchronized to gain performance improve, I removed idForNull and
fallback to 0.12.3 code.
private static class DimensionDictionary
{
private String minValue = null;
private String maxValue = null;
private final Object2IntMap<String> valueToId = new
Object2IntOpenHashMap<>();
private final List<String> idToValue = Lists.newArrayList();
private final Object lock;
public DimensionDictionary()
{
this.lock = new Object();
valueToId.defaultReturnValue(-1);
}
public int getId(String value)
{
return valueToId.getInt(Strings.nullToEmpty(value));
}
public String getValue(int id)
{
return Strings.emptyToNull(idToValue.get(id));
}
public int size()
{
return valueToId.size();
}
public int add(String originalValue)
{
String value = Strings.nullToEmpty(originalValue);
synchronized (lock) {
int prev = valueToId.getInt(value);
if (prev >= 0) {
return prev;
}
final int index = size();
valueToId.put(value, index);
idToValue.add(value);
minValue = minValue == null || minValue.compareTo(value) > 0 ? value :
minValue;
maxValue = maxValue == null || maxValue.compareTo(value) < 0 ? value :
maxValue;
return index;
}
}
public String getMinValue()
{
return minValue;
}
public String getMaxValue()
{
return maxValue;
}
public SortedDimensionDictionary sort()
{
synchronized (lock) {
return new SortedDimensionDictionary(idToValue, size());
}
}
}
[ Full content available at:
https://github.com/apache/incubator-druid/issues/6322 ]
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