[41] Fix count on all null VALUES clause #70
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* Test Count accumulator with all-nulls * Fix count on null values Before the change, the `ValuesExec` containing `NullArray` would incorrectly report column statistics as being non-null, which would misinform `AggregateStatistics` optimizer and fold `count(always_null)` into row count instead of 0. This commit fixes the column statistics derivation for values with `NullArray` and therefore fixes execution of logical plans with count over such values. Note that the bug was not reproducible using DataFusion SQL frontend, because in DataFusion SQL the `VALUES (NULL)` doesn't have type `DataType:Null` (it has some apparently arbitrarily picked type instead). As a follow-up, all usages of `Array:null_count` should be inspected. The function can easily be misused (it returns "physical nulls", which do not exist for null type).
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* Customize window frame support for dialect (#70) * Customize window frame support for dialect * fix: ignore frame only when frame implies no frame * Add comments. move the window frame determine logic to dialect method * Update datafusion/sql/src/unparser/dialect.rs * Update test case * fix --------- Co-authored-by: Phillip LeBlanc <[email protected]> * fix clippy --------- Co-authored-by: Phillip LeBlanc <[email protected]>
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Cherry pick apache#13029
Before the change, the
ValuesExeccontainingNullArraywould incorrectly report column statistics as being non-null, which would misinformAggregateStatisticsoptimizer and foldcount(always_null)into row count instead of 0.This commit fixes the column statistics derivation for values with
NullArrayand therefore fixes execution of logical plans with count over such values.Note that the bug was not reproducible using DataFusion SQL frontend, because in DataFusion SQL the
VALUES (NULL)doesn't have typeDataType:Null(it has some apparently arbitrarily picked type instead).As a follow-up, all usages of
Array:null_countshould be inspected. The function can easily be misused (it returns "physical nulls", which do not exist for null type).