Zoltán Borók-Nagy created IMPALA-8755:
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Summary: Implement Z-ordering for Impala
Key: IMPALA-8755
URL: https://issues.apache.org/jira/browse/IMPALA-8755
Project: IMPALA
Issue Type: New Feature
Reporter: Zoltán Borók-Nagy
Implement Z-ordering for Impala: [https://en.wikipedia.org/wiki/Z-order_curve]
A Z-order curve defines an ordering on multi-dimensional data. Data sorted that
way can be efficiently filtered by min/max statistics regarding to the columns
participating in the ordering.
Impala currently only supports lexicographic ordering via the SORT BY clause.
This strongly prefers the first column, i.e. given the "SORT BY A, B, C" clause
=> A will be totally ordered (hence filtering on A will be very efficient), but
values belonging to B and C will be scattered throughout the data set (hence
filtering on B or C will barely do any good).
We could add a new clause, e.g. a "ZSORT BY" clause to Impala that writes the
data in Z-order.
"ZSORT BY A, B C" would cluster the rows in a way that filtering on A, B, or C
would be equally efficient.
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