Jefffrey commented on code in PR #17255:
URL: https://github.com/apache/datafusion/pull/17255#discussion_r2295094013
##########
datafusion/functions-aggregate/src/average.rs:
##########
@@ -114,72 +115,88 @@ impl AggregateUDFImpl for Avg {
}
fn accumulator(&self, acc_args: AccumulatorArgs) -> Result<Box<dyn
Accumulator>> {
- if acc_args.is_distinct {
- return exec_err!("avg(DISTINCT) aggregations are not available");
- }
+ let data_type = acc_args.exprs[0].data_type(acc_args.schema)?;
use DataType::*;
- let data_type = acc_args.exprs[0].data_type(acc_args.schema)?;
// instantiate specialized accumulator based for the type
- match (&data_type, acc_args.return_field.data_type()) {
- (Float64, Float64) => Ok(Box::<AvgAccumulator>::default()),
- (
- Decimal128(sum_precision, sum_scale),
- Decimal128(target_precision, target_scale),
- ) => Ok(Box::new(DecimalAvgAccumulator::<Decimal128Type> {
- sum: None,
- count: 0,
- sum_scale: *sum_scale,
- sum_precision: *sum_precision,
- target_precision: *target_precision,
- target_scale: *target_scale,
- })),
-
- (
- Decimal256(sum_precision, sum_scale),
- Decimal256(target_precision, target_scale),
- ) => Ok(Box::new(DecimalAvgAccumulator::<Decimal256Type> {
- sum: None,
- count: 0,
- sum_scale: *sum_scale,
- sum_precision: *sum_precision,
- target_precision: *target_precision,
- target_scale: *target_scale,
- })),
-
- (Duration(time_unit), Duration(result_unit)) => {
- Ok(Box::new(DurationAvgAccumulator {
+ if acc_args.is_distinct {
+ match &data_type {
+ // Numeric types are converted to Float64 via
`coerce_avg_type` during logical plan creation
+ Float64 =>
Ok(Box::new(Float64DistinctAvgAccumulator::default())),
+ _ => exec_err!("AVG(DISTINCT) for {} not supported",
data_type),
+ }
+ } else {
+ match (&data_type, acc_args.return_field.data_type()) {
+ (Float64, Float64) => Ok(Box::<AvgAccumulator>::default()),
+ (
+ Decimal128(sum_precision, sum_scale),
+ Decimal128(target_precision, target_scale),
+ ) => Ok(Box::new(DecimalAvgAccumulator::<Decimal128Type> {
sum: None,
count: 0,
- time_unit: *time_unit,
- result_unit: *result_unit,
- }))
- }
+ sum_scale: *sum_scale,
+ sum_precision: *sum_precision,
+ target_precision: *target_precision,
+ target_scale: *target_scale,
+ })),
+
+ (
+ Decimal256(sum_precision, sum_scale),
+ Decimal256(target_precision, target_scale),
+ ) => Ok(Box::new(DecimalAvgAccumulator::<Decimal256Type> {
+ sum: None,
+ count: 0,
+ sum_scale: *sum_scale,
+ sum_precision: *sum_precision,
+ target_precision: *target_precision,
+ target_scale: *target_scale,
+ })),
+
+ (Duration(time_unit), Duration(result_unit)) => {
+ Ok(Box::new(DurationAvgAccumulator {
+ sum: None,
+ count: 0,
+ time_unit: *time_unit,
+ result_unit: *result_unit,
+ }))
+ }
- _ => exec_err!(
- "AvgAccumulator for ({} --> {})",
- &data_type,
- acc_args.return_field.data_type()
- ),
+ _ => exec_err!(
+ "AvgAccumulator for ({} --> {})",
+ &data_type,
+ acc_args.return_field.data_type()
+ ),
+ }
}
}
fn state_fields(&self, args: StateFieldsArgs) -> Result<Vec<FieldRef>> {
- Ok(vec![
- Field::new(
- format_state_name(args.name, "count"),
- DataType::UInt64,
- true,
- ),
- Field::new(
- format_state_name(args.name, "sum"),
- args.input_fields[0].data_type().clone(),
- true,
- ),
- ]
- .into_iter()
- .map(Arc::new)
- .collect())
+ if args.is_distinct {
+ // Copied from
datafusion_functions_aggregate::sum::Sum::state_fields
+ // since the accumulator uses DistinctSumAccumulator internally.
+ Ok(vec![Field::new_list(
+ format_state_name(args.name, "sum distinct"),
+ Field::new_list_field(args.return_type().clone(), true),
+ false,
+ )
+ .into()])
+ } else {
+ Ok(vec![
+ Field::new(
+ format_state_name(args.name, "count"),
+ DataType::UInt64,
+ true,
+ ),
+ Field::new(
+ format_state_name(args.name, "sum"),
+ args.input_fields[0].data_type().clone(),
+ true,
+ ),
+ ]
+ .into_iter()
+ .map(Arc::new)
+ .collect())
+ }
Review Comment:
Sorry, what I meant was that in accumulators we can return the `state()`
like so:
https://github.com/apache/datafusion/blob/be3842b55d61095d77aae54426726ddd1eed5f2c/datafusion/functions-aggregate/src/sum.rs#L432-L450
However this must align with `state_fields()` of the parent aggregate UDF:
https://github.com/apache/datafusion/blob/be3842b55d61095d77aae54426726ddd1eed5f2c/datafusion/functions-aggregate/src/sum.rs#L204-L221
But this isn't clearly obvious at compile time, and during runtime we only
hit this issue for certain test cases (for this distinct avg PR). So I was
wondering if there was a better way to enforce this at compile time. Hope that
clears it up.
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