Describe what enhancement you'd like to have
distinct_retract is a connector, distinct means filter the duplicate data to the next aggregation operator, and retract is the internal impl about CDC with changelog. (we use virtual column tp_delta, +1 means data in, and -1 means retract.)

short: this issue wanna tackle 2 things:

1. replace the map->hashmap, this file shall be found in https://github.com/timeplus-io/proton/blob/develop/src/AggregateFunctions/Streaming/CountedValueHashMap.h
2. add extra logic for numeric data.

detailed

Since we have introduced counted_value_hash_map in #484, the distinct still uses an ordered map, actually, the distinct connector does not care about the order of the element.
the related code can be found at

another thing we wanna improve/refactor is currently we use the stringRef style for all the input, recalling another distinct implementation, we notice the function has to do dispatch with input data type. that's say, current distinct_retract needs extra serialize/deser for numeric data, but, we are input the numeric data, we do not need such string serialization overhead.

upstream #426