jayzhan211 commented on code in PR #12296:
URL: https://github.com/apache/datafusion/pull/12296#discussion_r1759907412
##########
datafusion/physical-optimizer/src/aggregate_statistics.rs:
##########
@@ -140,155 +138,24 @@ fn take_optimizable_column_and_table_count(
agg_expr: &AggregateFunctionExpr,
stats: &Statistics,
) -> Option<(ScalarValue, String)> {
- let col_stats = &stats.column_statistics;
- if is_non_distinct_count(agg_expr) {
- if let Precision::Exact(num_rows) = stats.num_rows {
- let exprs = agg_expr.expressions();
- if exprs.len() == 1 {
- // TODO optimize with exprs other than Column
- if let Some(col_expr) =
- exprs[0].as_any().downcast_ref::<expressions::Column>()
- {
- let current_val = &col_stats[col_expr.index()].null_count;
- if let &Precision::Exact(val) = current_val {
- return Some((
- ScalarValue::Int64(Some((num_rows - val) as i64)),
- agg_expr.name().to_string(),
- ));
- }
- } else if let Some(lit_expr) =
- exprs[0].as_any().downcast_ref::<expressions::Literal>()
- {
- if lit_expr.value() == &COUNT_STAR_EXPANSION {
- return Some((
- ScalarValue::Int64(Some(num_rows as i64)),
- agg_expr.name().to_string(),
- ));
- }
- }
- }
- }
- }
- None
-}
-
-/// If this agg_expr is a min that is exactly defined in the statistics,
return it.
-fn take_optimizable_min(
- agg_expr: &AggregateFunctionExpr,
- stats: &Statistics,
-) -> Option<(ScalarValue, String)> {
- if let Precision::Exact(num_rows) = &stats.num_rows {
- match *num_rows {
- 0 => {
- // MIN/MAX with 0 rows is always null
- if is_min(agg_expr) {
- if let Ok(min_data_type) =
- ScalarValue::try_from(agg_expr.field().data_type())
- {
- return Some((min_data_type,
agg_expr.name().to_string()));
- }
- }
- }
- value if value > 0 => {
- let col_stats = &stats.column_statistics;
- if is_min(agg_expr) {
- let exprs = agg_expr.expressions();
- if exprs.len() == 1 {
- // TODO optimize with exprs other than Column
- if let Some(col_expr) =
-
exprs[0].as_any().downcast_ref::<expressions::Column>()
- {
- if let Precision::Exact(val) =
- &col_stats[col_expr.index()].min_value
- {
- if !val.is_null() {
- return Some((
- val.clone(),
- agg_expr.name().to_string(),
- ));
- }
- }
- }
- }
- }
- }
- _ => {}
+ if !agg_expr.is_distinct() {
+ if let Some((val, name)) =
take_optimizable_value_from_statistics(agg_expr, stats)
+ {
+ return Some((val, name));
}
}
None
}
/// If this agg_expr is a max that is exactly defined in the statistics,
return it.
-fn take_optimizable_max(
+fn take_optimizable_value_from_statistics(
agg_expr: &AggregateFunctionExpr,
stats: &Statistics,
) -> Option<(ScalarValue, String)> {
- if let Precision::Exact(num_rows) = &stats.num_rows {
- match *num_rows {
- 0 => {
- // MIN/MAX with 0 rows is always null
- if is_max(agg_expr) {
- if let Ok(max_data_type) =
- ScalarValue::try_from(agg_expr.field().data_type())
- {
- return Some((max_data_type,
agg_expr.name().to_string()));
- }
- }
- }
- value if value > 0 => {
- let col_stats = &stats.column_statistics;
- if is_max(agg_expr) {
- let exprs = agg_expr.expressions();
- if exprs.len() == 1 {
- // TODO optimize with exprs other than Column
- if let Some(col_expr) =
-
exprs[0].as_any().downcast_ref::<expressions::Column>()
- {
- if let Precision::Exact(val) =
- &col_stats[col_expr.index()].max_value
- {
- if !val.is_null() {
- return Some((
- val.clone(),
- agg_expr.name().to_string(),
- ));
- }
- }
- }
- }
- }
- }
- _ => {}
- }
- }
- None
+ let value = agg_expr.fun().value_from_stats(
Review Comment:
The optimization for count is mainly for `count(*)`, since it doesn't make
sense for distinct case, so we only care about `non-distinct count` for
`value_from_stats`, but not `distinct count`.
> It seems that distinct has specifically to do with the optimizer and not
with "getting a value for the specific UDF from statistics"
`distinct` is for `value_from_stats` to know what kind of function we have,
either `count` or `distinct count`.
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