Lars Hofhansl created PHOENIX-2797: -------------------------------------- Summary: Ideas to speed up MIN/MAX/DISTINCT for prefixes of the PK Key: PHOENIX-2797 URL: https://issues.apache.org/jira/browse/PHOENIX-2797 Project: Phoenix Issue Type: Improvement Reporter: Lars Hofhansl Priority: Minor
All of MIN, MAX, and DISTINCT always perform a full scan, even when they for a prefix of a compound key. For MIN and MAX only need to find the first and last row (resp) and we'll have our answer. This works for the full key or a prefix of the key. This should work find with or without a WHERE clause, as long as we can identify the first and last. For DISTINCT we could a skip scan to the next prefix (only help with a true prefix of a compound key). Say the key is (K1, K2), and say that we're doing DISTINCT(K1). We can skip to the next value of K1 once we found a value. This should have a dramatic impact when the cardinality of K2 is high. With a WHERE clause that might itself be causing a SKIP SCAN, this might be quite tricky. Would need to think about it. Both of these statement hold equally when querying against an index. Anyway... Just filing this as an idea for now. -- This message was sent by Atlassian JIRA (v6.3.4#6332)