James Taylor created PHOENIX-2700:
-------------------------------------
Summary: Push down count(group by key) queries
Key: PHOENIX-2700
URL: https://issues.apache.org/jira/browse/PHOENIX-2700
Project: Phoenix
Issue Type: Bug
Reporter: James Taylor
Queries that attempt to detect duplicates potentially return a lot of data to
the client if the column being deduped is near unique. For example:
{code}
SELECT SUM(DUP_COUNT)
FROM (
SELECT DEDUP_KEY, COUNT(1) As DUP_COUNT
FROM TABLE_TO_DEDUP
GROUP BY DEDUP_KEY
)
WHERE DUP_COUNT > 1
{code}
If all of the following are true, then we can detect duplicates on the region
server in our coprocessors instead of returning every unique DEDUP_KEY to the
client for a final merge:
- each scan won't be split on the same DEDUP_KEY
- the DEDUP_KEY is the leading primary key column
- we can push the DUP_COUNT > 1 evaluation through our coprocessor
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