Liya Fan created ARROW-6184:
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Summary: [Java] Provide hash table based dictionary encoder
Key: ARROW-6184
URL: https://issues.apache.org/jira/browse/ARROW-6184
Project: Apache Arrow
Issue Type: New Feature
Components: Java
Reporter: Liya Fan
Assignee: Liya Fan
This is the second part of ARROW-5917. We provide a sort based encoder, as well
as a hash table based encoder, to solve the problem with the current dictionary
encoder.
In particular, we solve the following problems with the current encoder:
# There are repeated conversions between Java objects and bytes (e.g.
vector.getObject(i)).
# Unnecessary memory copy (the vector data must be copied to the hash table).
# The hash table cannot be reused for encoding multiple vectors (other data
structure & results cannot be reused either).
# The output vector should not be created/managed by the encoder (just like in
the out-of-place sorter)
# The hash table requires that the hashCode & equals methods be implemented
appropriately, but this is not guaranteed.
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