James Taylor created PHOENIX-3773:
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Summary: Implement FIRST_VALUES aggregate function
Key: PHOENIX-3773
URL: https://issues.apache.org/jira/browse/PHOENIX-3773
Project: Phoenix
Issue Type: Bug
Reporter: James Taylor
Similar to FIRST_VALUE, but would allow the user to specify how many values to
keep. This could use a MinMaxPriorityQueue under the covers and be much more
efficient than using multiple NTH_VALUE calls to do the same like this:
{code}
SELECT entity_id,
NTH_VALUE(user_id,1) WITHIN GROUP (ORDER BY last_read_date DESC) as
nth1_user_id,
NTH_VALUE(user_id,2) WITHIN GROUP (ORDER BY last_read_date DESC) as
nth2_user_id,
NTH_VALUE(user_id,3) WITHIN GROUP (ORDER BY last_read_date DESC) as
nth3_user_id,
count(*)
FROM MY_TABLE
WHERE tenant_id='00Dx0000000XXXX'
AND entity_id in ('0D5x000000ABCD','0D5x000000ABCE')
GROUP BY entity_id;
{code}
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