Konstantin Orlov created IGNITE-18206:
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Summary: Sql. Prohibit using of DISTINCT&SORTED 2-phase aggregates
Key: IGNITE-18206
URL: https://issues.apache.org/jira/browse/IGNITE-18206
Project: Ignite
Issue Type: Improvement
Components: sql
Reporter: Konstantin Orlov
Currently, 2-phase aggregate is used even for aggregates with DISTINCT and
ORDER BY clauses. This is possible because of unnatural resulting row produced
by a MAP aggregate: in a single column it accumulates all rows belonging to a
particular group.
Such an approach causes errors in cost calculation, as well as closes the door
for further optimizations, like reusing BinaryTuple for sql row, because of a
complex structure of the row.
As a first step, let's prohibit using of 2-phase aggregates for cases where
collection of rows for particular row should be preserved in order to compute
the final result (DISTINCT&SORTED aggregates).
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