Liya Fan created ARROW-6933: ------------------------------- Summary: [Java] Suppor linear dictionary encoder Key: ARROW-6933 URL: https://issues.apache.org/jira/browse/ARROW-6933 Project: Apache Arrow Issue Type: New Feature Components: Java Reporter: Liya Fan Assignee: Liya Fan
For many scenarios, the distribution of dictionary entries is highly skewed. In other words, a few dictionary entries occurs much more frequently than others. If we can sort the dictionary by the non-increasing order of entry frequencies, and compare each value to encode from the beginning of the dictionary, we get the following benefits: 1) We need no extra memory space or data structure. 2) The search is extremely efficient, as we are likely to find a match in the first few entries of the dictionary. This is the basic idea behind the linear dictionary encoder. When the scenario is right (highly skewed dictionary distribution), it outperforms both search based encoder and hash table based encoders. -- This message was sent by Atlassian Jira (v8.3.4#803005)