appletreeisyellow commented on code in PR #9223:
URL: https://github.com/apache/arrow-datafusion/pull/9223#discussion_r1525651339
##########
datafusion/core/src/physical_optimizer/pruning.rs:
##########
@@ -1320,14 +1457,56 @@ fn build_statistics_expr(
);
}
};
+ let statistics_expr = wrap_case_expr(statistics_expr, expr_builder)?;
Ok(statistics_expr)
}
+/// Wrap the statistics expression in a case expression.
+/// This is necessary to handle the case where the column is known
+/// to be all nulls.
+///
+/// For example:
+///
+/// `x_min <= 10 AND 10 <= x_max`
+///
+/// will become
+///
+/// ```sql
+/// CASE
+/// WHEN x_null_count = x_row_count THEN false
+/// ELSE x_min <= 10 AND 10 <= x_max
+/// END
+/// ````
+///
+/// If the column is known to be all nulls, then the expression
+/// `x_null_count = x_row_count` will be true, which will cause the
+/// case expression to return false. Therefore, prune out the container.
+fn wrap_case_expr(
Review Comment:
I will consider it in a follow-up PR 👍
Tracked in
https://github.com/apache/arrow-datafusion/issues/9171#issuecomment-1998518531
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