clintropolis commented on a change in pull request #10613:
URL: https://github.com/apache/druid/pull/10613#discussion_r553814648
##########
File path:
processing/src/main/java/org/apache/druid/segment/DimensionHandlerUtils.java
##########
@@ -305,17 +305,29 @@ private static ColumnCapabilities
getEffectiveCapabilities(
originalCapabilities == null ||
ValueType.COMPLEX.equals(originalCapabilities.getType());
if (type == ValueType.STRING) {
- if (!forceSingleValue &&
effectiveCapabilites.hasMultipleValues().isMaybeTrue()) {
- return strategyFactory.makeMultiValueDimensionProcessor(
- effectiveCapabilites,
- selectorFactory.makeMultiValueDimensionSelector(dimensionSpec)
- );
- } else {
- return strategyFactory.makeSingleValueDimensionProcessor(
- effectiveCapabilites,
- selectorFactory.makeSingleValueDimensionSelector(dimensionSpec)
- );
+ if (!forceSingleValue) {
+ // if column is not dictionary encoded (and not non-existent or
complex), use object selector
+ if (effectiveCapabilites.isDictionaryEncoded().isFalse() ||
+ effectiveCapabilites.areDictionaryValuesUnique().isFalse()
Review comment:
by regular string selector do you mean dimension selector? The answer is
yes we _could_, but if the dictionary values are not unique, i came to the
conclusion that they aren't especially useful since in all the cases I can
think of you can't use them as is and you're going to have to lookup the string
values anyway (e.g. filter matching and vector group by).
I was trying to provide an avenue to avoid the extra steps with expression
virtual columns, and allow an object selector to be created directly since the
string is the useable part in this case, and the dictionary ids just feel like
an obstruction. But maybe this is overly broad and there are cases where we
would want it to act like a dictionary encoded column for some reason that I
have missed?
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