@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.
And for getValue(id), the id is impossible be greater than ArrayList.size() -1,
one should call add() first to get the maxId, also IndexOutOfBoundsException
won't happen here.
On the other hand, current synchronized/rw lock can't actually do what it means
to. 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 threadA getMinValue(), threadB add(), threadA now holds the outdated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 idToValue.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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