Aleksey Plekhanov created IGNITE-16013:
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Summary: Calcite engine. Introduce sort-with-limit physical
relational operator
Key: IGNITE-16013
URL: https://issues.apache.org/jira/browse/IGNITE-16013
Project: Ignite
Issue Type: Improvement
Reporter: Aleksey Plekhanov
Currently, sort and limit are different physical relational operators, but in
some cases, sort combined with a limit can be more effective. For example
{{ORDER BY x LIMIT 1}} requires to store only one row and can be processed with
{{O(rowsCount)}} operations. In general. {{ORDER BY x LIMIT m}} requires
{{O(min(rowsCount, m))}} memory and have {{O(rowsCount * ln(min(rowsCount,
m)))}} complexity.
Since {{Limit}} node can't be moved below the {{Exchange}} node, {{ORDER BY x
LIMIT m}} clause should produce two nodes: {{Limit}} node, with single
distribution, and {{SortWithLimit}} node, which can be moved below the
{{Exchange}} node and can reduce network traffic.
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