kumarUjjawal commented on code in PR #21765: URL: https://github.com/apache/datafusion/pull/21765#discussion_r3361326084
########## datafusion/physical-plan/src/aggregates/group_values/single_group_by/dictionary.rs: ########## @@ -0,0 +1,768 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +use crate::aggregates::group_values::GroupValues; +use crate::hash_utils::RandomState; +use arrow::array::{ + Array, ArrayRef, AsArray, DictionaryArray, LargeStringArray, LargeStringBuilder, + ListArray, ListBuilder, PrimitiveArray, PrimitiveBuilder, StringArray, StringBuilder, + StringViewArray, StringViewBuilder, +}; +use arrow::datatypes::{ArrowDictionaryKeyType, ArrowNativeType, DataType}; +use datafusion_common::DataFusionError::{Internal, NotImplemented}; +use datafusion_common::Result; +use datafusion_common::hash_utils::create_hashes; +use datafusion_expr::EmitTo; +use hashbrown::HashTable; +use hashbrown::hash_table::Entry as HashTableEntry; +use std::borrow::Cow; +use std::marker::PhantomData; +use std::sync::Arc; + +/// Heuristic for sizing the values buffer of string builders during emit: +/// dictionary-encoded values are short by design (categorical strings, short +/// identifiers), so 16 B/item avoids the realloc-doubling chain in the common +/// case while keeping over-allocation cheap when values are smaller. +const AVG_BYTES_PER_DICT_VALUE: usize = 16; +const INITIAL_PRE_ALLOCATION: usize = 8 * 1024; // avoid re-allocation`s for small-medium groups + +macro_rules! decode_list { + ($raw:expr, $builder:expr) => {{ + let mut builder = $builder; + for raw_bytes in $raw { + match raw_bytes { + None => builder.append_null(), + Some(raw_vector) => { + let mut offset = 0; + while offset < raw_vector.len() { + let len = i64::from_ne_bytes( + raw_vector[offset..offset + 8] + .try_into() + .expect("slice of length 8"), + ); + offset += 8; + if len == -1 { + builder.values().append_null(); + } else { + let s = unsafe { + std::str::from_utf8_unchecked( + &raw_vector[offset..offset + len as usize], + ) + }; + builder.values().append_value(s); + offset += len as usize; + } + } + builder.append(true); + } + } + } + Ok(Arc::new(builder.finish()) as ArrayRef) + }}; +} +macro_rules! decode_scalar_string { + ($raw:expr, $builder:expr) => {{ + let mut builder = $builder; + for raw_bytes in $raw { + match raw_bytes { + Some(raw_vector) => { + let s = unsafe { std::str::from_utf8_unchecked(raw_vector) }; + builder.append_value(s); + } + None => builder.append_null(), + } + } + Ok(Arc::new(builder.finish()) as ArrayRef) + }}; +} +/// Entry stored inside `unique_dict_value_mapping`. Caching `hash` on the entry +struct DictEntry { + hash: u64, + group_id: usize, + bytes: Vec<u8>, +} + +pub struct GroupValuesDictionary<K: ArrowDictionaryKeyType + Send> { + // stores the order new unique elements are seen for self.emit() + seen_elements: Vec<Option<Vec<u8>>>, + value_dt: DataType, + _phantom: PhantomData<K>, + // keeps track of which values weve already seen, keyed by raw value hash. + unique_dict_value_mapping: HashTable<DictEntry>, + + random_state: RandomState, + + // cache the group id for nulls since they all map to the same group + null_group_id: Option<usize>, + intern_called: bool, + // 0. cache pointer of arrays, this avoids having to re-compute hashing for arrays weve already seen on past iterations + // 1. avoid re-allocating buffer inbetween calls, instead of allocating a new vector each time re-use inbetween calls + values_cache: (Option<ArrayRef>, Vec<u64>), +} + +impl<K: ArrowDictionaryKeyType + Send> GroupValuesDictionary<K> { + pub fn new(data_type: &DataType) -> Self { + Self { + seen_elements: Vec::new(), + unique_dict_value_mapping: HashTable::with_capacity(INITIAL_PRE_ALLOCATION), + value_dt: data_type.clone(), + _phantom: PhantomData, + random_state: RandomState::with_seed(0), + null_group_id: None, + intern_called: false, + values_cache: (None, Vec::new()), + } + } + + /// Returns the existing `group_id` for the value with this hash and bytes, + /// or inserts a new entry and returns the freshly assigned group_id. + fn lookup_or_insert_in_table(&mut self, hash: u64, raw: &[u8]) -> usize { + match self + .unique_dict_value_mapping + .entry(hash, |e| e.bytes == raw, |e| e.hash) + { + HashTableEntry::Occupied(o) => o.get().group_id, + HashTableEntry::Vacant(v) => { + let new_group_id = self.seen_elements.len(); + self.seen_elements.push(Some(raw.to_vec())); // replace this with raw buffer to avoid this double copy #TODO see https://github.com/apache/datafusion/issues/22078 + v.insert(DictEntry { + hash, + group_id: new_group_id, + bytes: raw.to_vec(), + }); + new_group_id + } + } + } + fn compute_value_hashes(&mut self, values: &ArrayRef) -> Result<()> { + self.values_cache.1.clear(); + self.values_cache.1.resize(values.len(), 0); + create_hashes( + [Arc::clone(values)], + &self.random_state, + &mut self.values_cache.1, + )?; + Ok(()) + //Ok(hashes) + } + + fn get_raw_bytes(values: &ArrayRef, index: usize) -> Cow<'_, [u8]> { + match values.data_type() { + DataType::Utf8 => Cow::Borrowed( + values + .as_any() + .downcast_ref::<StringArray>() + .expect("Expected StringArray") + .value(index) + .as_bytes(), + ), + DataType::LargeUtf8 => Cow::Borrowed( + values + .as_any() + .downcast_ref::<LargeStringArray>() + .expect("Expected LargeStringArray") + .value(index) + .as_bytes(), + ), + DataType::Utf8View => Cow::Borrowed( + values + .as_any() + .downcast_ref::<StringViewArray>() + .expect("Expected StringViewArray") + .value(index) + .as_bytes(), + ), + DataType::List(_) => { + let list_array = values + .as_any() + .downcast_ref::<ListArray>() + .expect("Expected ListArray"); + + debug_assert!(!list_array.is_null(index)); + + let start = list_array.value_offsets()[index] as usize; + let end = list_array.value_offsets()[index + 1] as usize; + let child = list_array.values(); + + let mut bytes = Vec::new(); + for i in start..end { + if child.is_null(i) { + // acts as a marker for transform_into_array to write a null + bytes.extend_from_slice(&(-1i64).to_ne_bytes()); + } else { + let raw = Self::get_raw_bytes(child, i); + bytes.extend_from_slice(&(raw.len() as i64).to_ne_bytes()); + bytes.extend_from_slice(&raw); + } + } + Cow::Owned(bytes) + } + other => unimplemented!("get_raw_bytes not implemented for {other:?}"), + } + } + + #[inline] + fn get_null_group_id(&mut self) -> usize { + if let Some(group_id) = self.null_group_id { + group_id + } else { + let new_group_id = self.seen_elements.len(); + self.seen_elements.push(None); + self.null_group_id = Some(new_group_id); + new_group_id + } + } + fn transform_into_array(&self, raw: &[Option<Vec<u8>>]) -> Result<ArrayRef> { + let item_capacity = raw.len(); + let data_capacity = item_capacity * AVG_BYTES_PER_DICT_VALUE; + match &self.value_dt { + DataType::Utf8 => decode_scalar_string!( + raw, + StringBuilder::with_capacity(item_capacity, data_capacity) + ), + DataType::LargeUtf8 => decode_scalar_string!( + raw, + LargeStringBuilder::with_capacity(item_capacity, data_capacity) + ), + DataType::Utf8View => decode_scalar_string!( + raw, + StringViewBuilder::with_capacity(item_capacity) + ), + DataType::List(field) => match field.data_type() { + DataType::Utf8 => decode_list!( + raw, + ListBuilder::with_capacity( + StringBuilder::with_capacity(item_capacity, data_capacity), + item_capacity, + ) + ), + DataType::LargeUtf8 => decode_list!( + raw, + ListBuilder::with_capacity( + LargeStringBuilder::with_capacity(item_capacity, data_capacity), + item_capacity, + ) + ), + DataType::Utf8View => decode_list!( + raw, + ListBuilder::with_capacity( + StringViewBuilder::with_capacity(item_capacity), + item_capacity, + ) + ), + other => Err(NotImplemented(format!( Review Comment: When the results are built back into a list column, the inner part of the list gets a hardcoded name ("item"). But Parquet files name it "element". DataFusion checks that names match exactly when assembling the output, so the query blows up at runtime. Also proved with a test. when building the output, reuse the exact column description from the input table instead of letting the builder invent one. ########## datafusion/physical-plan/src/aggregates/group_values/single_group_by/dictionary.rs: ########## @@ -0,0 +1,768 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +use crate::aggregates::group_values::GroupValues; +use crate::hash_utils::RandomState; +use arrow::array::{ + Array, ArrayRef, AsArray, DictionaryArray, LargeStringArray, LargeStringBuilder, + ListArray, ListBuilder, PrimitiveArray, PrimitiveBuilder, StringArray, StringBuilder, + StringViewArray, StringViewBuilder, +}; +use arrow::datatypes::{ArrowDictionaryKeyType, ArrowNativeType, DataType}; +use datafusion_common::DataFusionError::{Internal, NotImplemented}; +use datafusion_common::Result; +use datafusion_common::hash_utils::create_hashes; +use datafusion_expr::EmitTo; +use hashbrown::HashTable; +use hashbrown::hash_table::Entry as HashTableEntry; +use std::borrow::Cow; +use std::marker::PhantomData; +use std::sync::Arc; + +/// Heuristic for sizing the values buffer of string builders during emit: +/// dictionary-encoded values are short by design (categorical strings, short +/// identifiers), so 16 B/item avoids the realloc-doubling chain in the common +/// case while keeping over-allocation cheap when values are smaller. +const AVG_BYTES_PER_DICT_VALUE: usize = 16; +const INITIAL_PRE_ALLOCATION: usize = 8 * 1024; // avoid re-allocation`s for small-medium groups + +macro_rules! decode_list { + ($raw:expr, $builder:expr) => {{ + let mut builder = $builder; + for raw_bytes in $raw { + match raw_bytes { + None => builder.append_null(), + Some(raw_vector) => { + let mut offset = 0; + while offset < raw_vector.len() { + let len = i64::from_ne_bytes( + raw_vector[offset..offset + 8] + .try_into() + .expect("slice of length 8"), + ); + offset += 8; + if len == -1 { + builder.values().append_null(); + } else { + let s = unsafe { + std::str::from_utf8_unchecked( + &raw_vector[offset..offset + len as usize], + ) + }; + builder.values().append_value(s); + offset += len as usize; + } + } + builder.append(true); + } + } + } + Ok(Arc::new(builder.finish()) as ArrayRef) + }}; +} +macro_rules! decode_scalar_string { + ($raw:expr, $builder:expr) => {{ + let mut builder = $builder; + for raw_bytes in $raw { + match raw_bytes { + Some(raw_vector) => { + let s = unsafe { std::str::from_utf8_unchecked(raw_vector) }; + builder.append_value(s); + } + None => builder.append_null(), + } + } + Ok(Arc::new(builder.finish()) as ArrayRef) + }}; +} +/// Entry stored inside `unique_dict_value_mapping`. Caching `hash` on the entry +struct DictEntry { + hash: u64, + group_id: usize, + bytes: Vec<u8>, +} + +pub struct GroupValuesDictionary<K: ArrowDictionaryKeyType + Send> { + // stores the order new unique elements are seen for self.emit() + seen_elements: Vec<Option<Vec<u8>>>, + value_dt: DataType, + _phantom: PhantomData<K>, + // keeps track of which values weve already seen, keyed by raw value hash. + unique_dict_value_mapping: HashTable<DictEntry>, + + random_state: RandomState, + + // cache the group id for nulls since they all map to the same group + null_group_id: Option<usize>, + intern_called: bool, + // 0. cache pointer of arrays, this avoids having to re-compute hashing for arrays weve already seen on past iterations + // 1. avoid re-allocating buffer inbetween calls, instead of allocating a new vector each time re-use inbetween calls + values_cache: (Option<ArrayRef>, Vec<u64>), +} + +impl<K: ArrowDictionaryKeyType + Send> GroupValuesDictionary<K> { + pub fn new(data_type: &DataType) -> Self { + Self { + seen_elements: Vec::new(), + unique_dict_value_mapping: HashTable::with_capacity(INITIAL_PRE_ALLOCATION), + value_dt: data_type.clone(), + _phantom: PhantomData, + random_state: RandomState::with_seed(0), + null_group_id: None, + intern_called: false, + values_cache: (None, Vec::new()), + } + } + + /// Returns the existing `group_id` for the value with this hash and bytes, + /// or inserts a new entry and returns the freshly assigned group_id. + fn lookup_or_insert_in_table(&mut self, hash: u64, raw: &[u8]) -> usize { + match self + .unique_dict_value_mapping + .entry(hash, |e| e.bytes == raw, |e| e.hash) + { + HashTableEntry::Occupied(o) => o.get().group_id, + HashTableEntry::Vacant(v) => { + let new_group_id = self.seen_elements.len(); + self.seen_elements.push(Some(raw.to_vec())); // replace this with raw buffer to avoid this double copy #TODO see https://github.com/apache/datafusion/issues/22078 + v.insert(DictEntry { + hash, + group_id: new_group_id, + bytes: raw.to_vec(), + }); + new_group_id + } + } + } + fn compute_value_hashes(&mut self, values: &ArrayRef) -> Result<()> { + self.values_cache.1.clear(); + self.values_cache.1.resize(values.len(), 0); + create_hashes( + [Arc::clone(values)], + &self.random_state, + &mut self.values_cache.1, + )?; + Ok(()) + //Ok(hashes) + } + + fn get_raw_bytes(values: &ArrayRef, index: usize) -> Cow<'_, [u8]> { + match values.data_type() { + DataType::Utf8 => Cow::Borrowed( + values + .as_any() + .downcast_ref::<StringArray>() + .expect("Expected StringArray") + .value(index) + .as_bytes(), + ), + DataType::LargeUtf8 => Cow::Borrowed( + values + .as_any() + .downcast_ref::<LargeStringArray>() + .expect("Expected LargeStringArray") + .value(index) + .as_bytes(), + ), + DataType::Utf8View => Cow::Borrowed( + values + .as_any() + .downcast_ref::<StringViewArray>() + .expect("Expected StringViewArray") + .value(index) + .as_bytes(), + ), + DataType::List(_) => { + let list_array = values + .as_any() + .downcast_ref::<ListArray>() + .expect("Expected ListArray"); + + debug_assert!(!list_array.is_null(index)); + + let start = list_array.value_offsets()[index] as usize; + let end = list_array.value_offsets()[index + 1] as usize; + let child = list_array.values(); + + let mut bytes = Vec::new(); + for i in start..end { + if child.is_null(i) { + // acts as a marker for transform_into_array to write a null + bytes.extend_from_slice(&(-1i64).to_ne_bytes()); + } else { + let raw = Self::get_raw_bytes(child, i); + bytes.extend_from_slice(&(raw.len() as i64).to_ne_bytes()); + bytes.extend_from_slice(&raw); + } + } + Cow::Owned(bytes) + } + other => unimplemented!("get_raw_bytes not implemented for {other:?}"), + } + } + + #[inline] + fn get_null_group_id(&mut self) -> usize { + if let Some(group_id) = self.null_group_id { + group_id + } else { + let new_group_id = self.seen_elements.len(); + self.seen_elements.push(None); + self.null_group_id = Some(new_group_id); + new_group_id + } + } + fn transform_into_array(&self, raw: &[Option<Vec<u8>>]) -> Result<ArrayRef> { + let item_capacity = raw.len(); + let data_capacity = item_capacity * AVG_BYTES_PER_DICT_VALUE; + match &self.value_dt { + DataType::Utf8 => decode_scalar_string!( + raw, + StringBuilder::with_capacity(item_capacity, data_capacity) + ), + DataType::LargeUtf8 => decode_scalar_string!( + raw, + LargeStringBuilder::with_capacity(item_capacity, data_capacity) + ), + DataType::Utf8View => decode_scalar_string!( + raw, + StringViewBuilder::with_capacity(item_capacity) + ), + DataType::List(field) => match field.data_type() { + DataType::Utf8 => decode_list!( + raw, + ListBuilder::with_capacity( + StringBuilder::with_capacity(item_capacity, data_capacity), + item_capacity, + ) + ), + DataType::LargeUtf8 => decode_list!( + raw, + ListBuilder::with_capacity( + LargeStringBuilder::with_capacity(item_capacity, data_capacity), + item_capacity, + ) + ), + DataType::Utf8View => decode_list!( + raw, + ListBuilder::with_capacity( + StringViewBuilder::with_capacity(item_capacity), + item_capacity, + ) + ), + other => Err(NotImplemented(format!( + "transform_into_array not implemented for List<{other:?}>" + ))), + }, + other => Err(NotImplemented(format!( + "transform_into_array not implemented for {other:?}" + ))), + } + } +} + +impl<K: ArrowDictionaryKeyType + Send> GroupValues for GroupValuesDictionary<K> { + fn size(&self) -> usize { + let seen_elements_size = self.seen_elements.capacity() + * size_of::<Option<Vec<u8>>>() + + self + .seen_elements + .iter() + .filter_map(|opt| opt.as_ref()) + .map(|inner| inner.capacity()) + .sum::<usize>(); + + let unique_mapping_size = self.unique_dict_value_mapping.capacity() + * size_of::<DictEntry>() + + self + .unique_dict_value_mapping + .iter() + .map(|e| e.bytes.capacity()) + .sum::<usize>(); + + let values_cache_size = self.values_cache.1.capacity() * size_of::<u64>() + + self + .values_cache + .0 + .as_ref() + .map(|a| a.to_data().get_array_memory_size()) + .unwrap_or(0); + + size_of::<Self>() + seen_elements_size + unique_mapping_size + values_cache_size + } + fn len(&self) -> usize { + self.seen_elements.len() + } + fn is_empty(&self) -> bool { + self.seen_elements.is_empty() + } + fn intern(&mut self, cols: &[ArrayRef], groups: &mut Vec<usize>) -> Result<()> { + assert_eq!( + cols.len(), + 1, + "GroupValuesDictionary only supports a single column" + ); + let array = Arc::clone(&cols[0]); + groups.clear(); // zero out buffer + let dict_array = array + .as_dictionary_opt() + .map_or_else(|| Err(Internal("Expected dictionary array".into())), Ok)?; + + let values = dict_array.values(); + let key_array: &PrimitiveArray<K> = dict_array.keys(); + if key_array.is_empty() { + return Ok(()); + } + + let cache_hit = self + .values_cache + .0 + .as_ref() + .map(|cached| Arc::ptr_eq(cached, values)) + .unwrap_or(false); + + if !cache_hit { + // values array changed since last batch - recompute hashes and update cached pointer + self.compute_value_hashes(values)?; + self.values_cache.0 = Some(Arc::clone(values)); + } + let mut key_to_group: Vec<Option<usize>> = vec![None; values.len()]; Review Comment: Each time a chunk of data arrives, we builds a brand new list with one slot per dictionary entry, uses it, and throws it away. When the dictionary is large allocation is repeated over and over. We should keep one scratch list on the tracker and reuse it between chunks ########## datafusion/physical-plan/src/aggregates/group_values/single_group_by/dictionary.rs: ########## @@ -0,0 +1,783 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +use crate::aggregates::group_values::GroupValues; +use crate::hash_utils::RandomState; +use arrow::array::{ + Array, ArrayRef, DictionaryArray, LargeStringArray, LargeStringBuilder, ListArray, + ListBuilder, PrimitiveArray, PrimitiveBuilder, StringArray, StringBuilder, + StringViewArray, StringViewBuilder, +}; +use arrow::datatypes::{ArrowDictionaryKeyType, ArrowNativeType, DataType}; +use datafusion_common::DataFusionError::{Internal, NotImplemented}; +use datafusion_common::Result; +use datafusion_common::hash_utils::create_hashes; +use datafusion_expr::EmitTo; +use hashbrown::HashTable; +use hashbrown::hash_table::Entry as HashTableEntry; +use std::borrow::Cow; +use std::marker::PhantomData; +use std::sync::Arc; + +/// Heuristic for sizing the values buffer of string builders during emit: +/// dictionary-encoded values are short by design (categorical strings, short +/// identifiers), so 16 B/item avoids the realloc-doubling chain in the common +/// case while keeping over-allocation cheap when values are smaller. +const AVG_BYTES_PER_DICT_VALUE: usize = 16; +const INITIAL_PRE_ALLOCATION: usize = 8 * 1024; // avoid re-allocation`s for small-medium groups + +macro_rules! decode_list { + ($raw:expr, $builder:expr) => {{ + let mut builder = $builder; + for raw_bytes in $raw { + match raw_bytes { + None => builder.append_null(), + Some(raw_vector) => { + let mut offset = 0; + while offset < raw_vector.len() { + let len = i64::from_ne_bytes( + raw_vector[offset..offset + 8] + .try_into() + .expect("slice of length 8"), + ); + offset += 8; + if len == -1 { + builder.values().append_null(); + } else { + let s = unsafe { + std::str::from_utf8_unchecked( + &raw_vector[offset..offset + len as usize], + ) + }; + builder.values().append_value(s); + offset += len as usize; + } + } + builder.append(true); + } + } + } + Ok(Arc::new(builder.finish()) as ArrayRef) + }}; +} +macro_rules! decode_scalar_string { + ($raw:expr, $builder:expr) => {{ + let mut builder = $builder; + for raw_bytes in $raw { + match raw_bytes { + Some(raw_vector) => { + let s = unsafe { std::str::from_utf8_unchecked(raw_vector) }; + builder.append_value(s); + } + None => builder.append_null(), + } + } + Ok(Arc::new(builder.finish()) as ArrayRef) + }}; +} +/// Entry stored inside `unique_dict_value_mapping`. Caching `hash` on the entry +struct DictEntry { + hash: u64, + group_id: usize, + bytes: Vec<u8>, +} + +pub struct GroupValuesDictionary<K: ArrowDictionaryKeyType + Send> { + // stores the order new unique elements are seen for self.emit() + seen_elements: Vec<Option<Vec<u8>>>, + value_dt: DataType, + _phantom: PhantomData<K>, + // keeps track of which values weve already seen, keyed by raw value hash. + unique_dict_value_mapping: HashTable<DictEntry>, + + random_state: RandomState, + + // cache the group id for nulls since they all map to the same group + null_group_id: Option<usize>, + intern_called: bool, + // 0. cache pointer of arrays, this avoids having to re-compute hashing for arrays weve already seen on past iterations + // 1. avoid re-allocating buffer inbetween calls, instead of allocating a new vector each time re-use inbetween calls + values_cache: (Option<ArrayRef>, Vec<u64>), +} + +impl<K: ArrowDictionaryKeyType + Send> GroupValuesDictionary<K> { + pub fn new(data_type: &DataType) -> Self { + Self { + seen_elements: Vec::new(), + unique_dict_value_mapping: HashTable::with_capacity(INITIAL_PRE_ALLOCATION), + value_dt: data_type.clone(), + _phantom: PhantomData, + random_state: RandomState::with_seed(0), + null_group_id: None, + intern_called: false, + values_cache: (None, Vec::new()), + } + } + + /// Returns the existing `group_id` for the value with this hash and bytes, + /// or inserts a new entry and returns the freshly assigned group_id. + fn lookup_or_insert_in_table(&mut self, hash: u64, raw: &[u8]) -> usize { + match self + .unique_dict_value_mapping + .entry(hash, |e| e.bytes == raw, |e| e.hash) + { + HashTableEntry::Occupied(o) => o.get().group_id, + HashTableEntry::Vacant(v) => { + let new_group_id = self.seen_elements.len(); + self.seen_elements.push(Some(raw.to_vec())); // replace this with raw buffer to avoid this double copy #TODO see https://github.com/apache/datafusion/issues/22078 + v.insert(DictEntry { + hash, + group_id: new_group_id, + bytes: raw.to_vec(), + }); + new_group_id + } + } + } + fn compute_value_hashes(&mut self, values: &ArrayRef) -> Result<()> { + self.values_cache.1.clear(); + self.values_cache.1.resize(values.len(), 0); + create_hashes( + [Arc::clone(values)], + &self.random_state, + &mut self.values_cache.1, + )?; + Ok(()) + //Ok(hashes) + } + + fn get_raw_bytes(values: &ArrayRef, index: usize) -> Cow<'_, [u8]> { + match values.data_type() { + DataType::Utf8 => Cow::Borrowed( + values + .as_any() + .downcast_ref::<StringArray>() + .expect("Expected StringArray") + .value(index) + .as_bytes(), + ), + DataType::LargeUtf8 => Cow::Borrowed( + values + .as_any() + .downcast_ref::<LargeStringArray>() + .expect("Expected LargeStringArray") + .value(index) + .as_bytes(), + ), + DataType::Utf8View => Cow::Borrowed( + values + .as_any() + .downcast_ref::<StringViewArray>() + .expect("Expected StringViewArray") + .value(index) + .as_bytes(), + ), + DataType::List(_) => { + let list_array = values + .as_any() + .downcast_ref::<ListArray>() + .expect("Expected ListArray"); + + debug_assert!(!list_array.is_null(index)); + + let start = list_array.value_offsets()[index] as usize; + let end = list_array.value_offsets()[index + 1] as usize; + let child = list_array.values(); + + let mut bytes = Vec::new(); + for i in start..end { + if child.is_null(i) { + // acts as a marker for transform_into_array to write a null + bytes.extend_from_slice(&(-1i64).to_ne_bytes()); + } else { + let raw = Self::get_raw_bytes(child, i); + bytes.extend_from_slice(&(raw.len() as i64).to_ne_bytes()); + bytes.extend_from_slice(&raw); + } + } + Cow::Owned(bytes) + } + other => unimplemented!("get_raw_bytes not implemented for {other:?}"), + } + } + + #[inline] + fn get_null_group_id(&mut self) -> usize { + if let Some(group_id) = self.null_group_id { + group_id + } else { + let new_group_id = self.seen_elements.len(); + self.seen_elements.push(None); + self.null_group_id = Some(new_group_id); + new_group_id + } + } + fn transform_into_array(&self, raw: &[Option<Vec<u8>>]) -> Result<ArrayRef> { + let item_capacity = raw.len(); + let data_capacity = item_capacity * AVG_BYTES_PER_DICT_VALUE; + match &self.value_dt { + DataType::Utf8 => decode_scalar_string!( + raw, + StringBuilder::with_capacity(item_capacity, data_capacity) + ), + DataType::LargeUtf8 => decode_scalar_string!( + raw, + LargeStringBuilder::with_capacity(item_capacity, data_capacity) + ), + DataType::Utf8View => decode_scalar_string!( + raw, + StringViewBuilder::with_capacity(item_capacity) + ), + DataType::List(field) => match field.data_type() { + DataType::Utf8 => decode_list!( + raw, + ListBuilder::with_capacity( + StringBuilder::with_capacity(item_capacity, data_capacity), + item_capacity, + ) + ), + DataType::LargeUtf8 => decode_list!( + raw, + ListBuilder::with_capacity( + LargeStringBuilder::with_capacity(item_capacity, data_capacity), + item_capacity, + ) + ), + DataType::Utf8View => decode_list!( + raw, + ListBuilder::with_capacity( + StringViewBuilder::with_capacity(item_capacity), + item_capacity, + ) + ), + other => Err(NotImplemented(format!( + "transform_into_array not implemented for List<{other:?}>" + ))), + }, + other => Err(NotImplemented(format!( + "transform_into_array not implemented for {other:?}" + ))), + } + } + #[inline] + fn keys_to_usize(key_array: &PrimitiveArray<K>) -> Vec<Option<usize>> { + (0..key_array.len()) + .map(|i| { + if key_array.is_null(i) { + None + } else { + Some(key_array.value(i).to_usize().unwrap()) + } + }) + .collect() + } +} + +impl<K: ArrowDictionaryKeyType + Send> GroupValues for GroupValuesDictionary<K> { + fn size(&self) -> usize { + let seen_elements_size = self.seen_elements.capacity() + * size_of::<Option<Vec<u8>>>() + + self + .seen_elements + .iter() + .filter_map(|opt| opt.as_ref()) + .map(|inner| inner.capacity()) + .sum::<usize>(); + + let unique_mapping_size = self.unique_dict_value_mapping.capacity() + * size_of::<DictEntry>() + + self + .unique_dict_value_mapping + .iter() + .map(|e| e.bytes.capacity()) + .sum::<usize>(); + + let values_cache_size = self.values_cache.1.capacity() * size_of::<u64>() + + self + .values_cache + .0 + .as_ref() + .map(|a| a.get_array_memory_size()) + .unwrap_or(0); + + size_of::<Self>() + seen_elements_size + unique_mapping_size + values_cache_size + } + fn len(&self) -> usize { + self.seen_elements.len() + } + fn is_empty(&self) -> bool { + self.seen_elements.is_empty() + } + fn intern(&mut self, cols: &[ArrayRef], groups: &mut Vec<usize>) -> Result<()> { + assert_eq!( + cols.len(), + 1, + "GroupValuesDictionary only supports a single column" + ); + let array = Arc::clone(&cols[0]); + groups.clear(); // zero out buffer + let dict_array = array + .as_any() + .downcast_ref::<DictionaryArray<K>>() + .ok_or_else(|| { + Internal(format!( + "GroupValuesDictionary expected DictionaryArray but got {:?}", + array.data_type() + )) + })?; + + let values = dict_array.values(); + let key_array = dict_array.keys(); + if key_array.is_empty() { + return Ok(()); + } + let keys_as_usize: Vec<Option<usize>> = Self::keys_to_usize(key_array); + + let cache_hit = self + .values_cache + .0 + .as_ref() + .map(|cached| Arc::ptr_eq(cached, values)) + .unwrap_or(false); + + if !cache_hit { + // first time seeing this values array to compute hashes, and cache the pointer, cheap operation + self.compute_value_hashes(values)?; + self.values_cache.0 = Some(Arc::clone(values)); + } + let mut key_to_group: Vec<Option<usize>> = vec![None; values.len()]; + if self.intern_called { Review Comment: I think this whole pre-scan block can be removed. The main loop below already does at most one table lookup per unique dictionary entry and caches the result so the pre-scan doesn't save any lookups, it just moves them earlier and adds a second full pass over the keys. ########## datafusion/physical-plan/src/aggregates/group_values/single_group_by/dictionary.rs: ########## @@ -0,0 +1,768 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +use crate::aggregates::group_values::GroupValues; +use crate::hash_utils::RandomState; +use arrow::array::{ + Array, ArrayRef, AsArray, DictionaryArray, LargeStringArray, LargeStringBuilder, + ListArray, ListBuilder, PrimitiveArray, PrimitiveBuilder, StringArray, StringBuilder, + StringViewArray, StringViewBuilder, +}; +use arrow::datatypes::{ArrowDictionaryKeyType, ArrowNativeType, DataType}; +use datafusion_common::DataFusionError::{Internal, NotImplemented}; +use datafusion_common::Result; +use datafusion_common::hash_utils::create_hashes; +use datafusion_expr::EmitTo; +use hashbrown::HashTable; +use hashbrown::hash_table::Entry as HashTableEntry; +use std::borrow::Cow; +use std::marker::PhantomData; +use std::sync::Arc; + +/// Heuristic for sizing the values buffer of string builders during emit: +/// dictionary-encoded values are short by design (categorical strings, short +/// identifiers), so 16 B/item avoids the realloc-doubling chain in the common +/// case while keeping over-allocation cheap when values are smaller. +const AVG_BYTES_PER_DICT_VALUE: usize = 16; +const INITIAL_PRE_ALLOCATION: usize = 8 * 1024; // avoid re-allocation`s for small-medium groups + +macro_rules! decode_list { + ($raw:expr, $builder:expr) => {{ + let mut builder = $builder; + for raw_bytes in $raw { + match raw_bytes { + None => builder.append_null(), + Some(raw_vector) => { + let mut offset = 0; + while offset < raw_vector.len() { + let len = i64::from_ne_bytes( + raw_vector[offset..offset + 8] + .try_into() + .expect("slice of length 8"), + ); + offset += 8; + if len == -1 { + builder.values().append_null(); + } else { + let s = unsafe { + std::str::from_utf8_unchecked( + &raw_vector[offset..offset + len as usize], + ) + }; + builder.values().append_value(s); + offset += len as usize; + } + } + builder.append(true); + } + } + } + Ok(Arc::new(builder.finish()) as ArrayRef) + }}; +} +macro_rules! decode_scalar_string { + ($raw:expr, $builder:expr) => {{ + let mut builder = $builder; + for raw_bytes in $raw { + match raw_bytes { + Some(raw_vector) => { + let s = unsafe { std::str::from_utf8_unchecked(raw_vector) }; + builder.append_value(s); + } + None => builder.append_null(), + } + } + Ok(Arc::new(builder.finish()) as ArrayRef) + }}; +} +/// Entry stored inside `unique_dict_value_mapping`. Caching `hash` on the entry +struct DictEntry { + hash: u64, + group_id: usize, + bytes: Vec<u8>, +} + +pub struct GroupValuesDictionary<K: ArrowDictionaryKeyType + Send> { + // stores the order new unique elements are seen for self.emit() + seen_elements: Vec<Option<Vec<u8>>>, + value_dt: DataType, + _phantom: PhantomData<K>, + // keeps track of which values weve already seen, keyed by raw value hash. + unique_dict_value_mapping: HashTable<DictEntry>, + + random_state: RandomState, + + // cache the group id for nulls since they all map to the same group + null_group_id: Option<usize>, + intern_called: bool, + // 0. cache pointer of arrays, this avoids having to re-compute hashing for arrays weve already seen on past iterations + // 1. avoid re-allocating buffer inbetween calls, instead of allocating a new vector each time re-use inbetween calls + values_cache: (Option<ArrayRef>, Vec<u64>), +} + +impl<K: ArrowDictionaryKeyType + Send> GroupValuesDictionary<K> { + pub fn new(data_type: &DataType) -> Self { + Self { + seen_elements: Vec::new(), + unique_dict_value_mapping: HashTable::with_capacity(INITIAL_PRE_ALLOCATION), + value_dt: data_type.clone(), + _phantom: PhantomData, + random_state: RandomState::with_seed(0), + null_group_id: None, + intern_called: false, + values_cache: (None, Vec::new()), + } + } + + /// Returns the existing `group_id` for the value with this hash and bytes, + /// or inserts a new entry and returns the freshly assigned group_id. + fn lookup_or_insert_in_table(&mut self, hash: u64, raw: &[u8]) -> usize { + match self + .unique_dict_value_mapping + .entry(hash, |e| e.bytes == raw, |e| e.hash) + { + HashTableEntry::Occupied(o) => o.get().group_id, + HashTableEntry::Vacant(v) => { + let new_group_id = self.seen_elements.len(); + self.seen_elements.push(Some(raw.to_vec())); // replace this with raw buffer to avoid this double copy #TODO see https://github.com/apache/datafusion/issues/22078 + v.insert(DictEntry { + hash, + group_id: new_group_id, + bytes: raw.to_vec(), + }); + new_group_id + } + } + } + fn compute_value_hashes(&mut self, values: &ArrayRef) -> Result<()> { + self.values_cache.1.clear(); + self.values_cache.1.resize(values.len(), 0); + create_hashes( + [Arc::clone(values)], + &self.random_state, + &mut self.values_cache.1, + )?; + Ok(()) + //Ok(hashes) + } + + fn get_raw_bytes(values: &ArrayRef, index: usize) -> Cow<'_, [u8]> { + match values.data_type() { + DataType::Utf8 => Cow::Borrowed( + values + .as_any() + .downcast_ref::<StringArray>() + .expect("Expected StringArray") + .value(index) + .as_bytes(), + ), + DataType::LargeUtf8 => Cow::Borrowed( + values + .as_any() + .downcast_ref::<LargeStringArray>() + .expect("Expected LargeStringArray") + .value(index) + .as_bytes(), + ), + DataType::Utf8View => Cow::Borrowed( + values + .as_any() + .downcast_ref::<StringViewArray>() + .expect("Expected StringViewArray") + .value(index) + .as_bytes(), + ), + DataType::List(_) => { + let list_array = values + .as_any() + .downcast_ref::<ListArray>() + .expect("Expected ListArray"); + + debug_assert!(!list_array.is_null(index)); + + let start = list_array.value_offsets()[index] as usize; + let end = list_array.value_offsets()[index + 1] as usize; + let child = list_array.values(); + + let mut bytes = Vec::new(); + for i in start..end { + if child.is_null(i) { + // acts as a marker for transform_into_array to write a null + bytes.extend_from_slice(&(-1i64).to_ne_bytes()); + } else { + let raw = Self::get_raw_bytes(child, i); + bytes.extend_from_slice(&(raw.len() as i64).to_ne_bytes()); + bytes.extend_from_slice(&raw); + } + } + Cow::Owned(bytes) + } + other => unimplemented!("get_raw_bytes not implemented for {other:?}"), + } + } + + #[inline] + fn get_null_group_id(&mut self) -> usize { + if let Some(group_id) = self.null_group_id { + group_id + } else { + let new_group_id = self.seen_elements.len(); + self.seen_elements.push(None); + self.null_group_id = Some(new_group_id); + new_group_id + } + } + fn transform_into_array(&self, raw: &[Option<Vec<u8>>]) -> Result<ArrayRef> { + let item_capacity = raw.len(); + let data_capacity = item_capacity * AVG_BYTES_PER_DICT_VALUE; + match &self.value_dt { + DataType::Utf8 => decode_scalar_string!( + raw, + StringBuilder::with_capacity(item_capacity, data_capacity) + ), + DataType::LargeUtf8 => decode_scalar_string!( + raw, + LargeStringBuilder::with_capacity(item_capacity, data_capacity) + ), + DataType::Utf8View => decode_scalar_string!( + raw, + StringViewBuilder::with_capacity(item_capacity) + ), + DataType::List(field) => match field.data_type() { + DataType::Utf8 => decode_list!( + raw, + ListBuilder::with_capacity( + StringBuilder::with_capacity(item_capacity, data_capacity), + item_capacity, + ) + ), + DataType::LargeUtf8 => decode_list!( + raw, + ListBuilder::with_capacity( + LargeStringBuilder::with_capacity(item_capacity, data_capacity), + item_capacity, + ) + ), + DataType::Utf8View => decode_list!( + raw, + ListBuilder::with_capacity( + StringViewBuilder::with_capacity(item_capacity), + item_capacity, + ) + ), + other => Err(NotImplemented(format!( + "transform_into_array not implemented for List<{other:?}>" + ))), + }, + other => Err(NotImplemented(format!( + "transform_into_array not implemented for {other:?}" + ))), + } + } +} + +impl<K: ArrowDictionaryKeyType + Send> GroupValues for GroupValuesDictionary<K> { + fn size(&self) -> usize { + let seen_elements_size = self.seen_elements.capacity() + * size_of::<Option<Vec<u8>>>() + + self + .seen_elements + .iter() + .filter_map(|opt| opt.as_ref()) + .map(|inner| inner.capacity()) + .sum::<usize>(); + + let unique_mapping_size = self.unique_dict_value_mapping.capacity() + * size_of::<DictEntry>() + + self + .unique_dict_value_mapping + .iter() + .map(|e| e.bytes.capacity()) + .sum::<usize>(); + + let values_cache_size = self.values_cache.1.capacity() * size_of::<u64>() + + self + .values_cache + .0 + .as_ref() + .map(|a| a.to_data().get_array_memory_size()) + .unwrap_or(0); + + size_of::<Self>() + seen_elements_size + unique_mapping_size + values_cache_size + } + fn len(&self) -> usize { + self.seen_elements.len() + } + fn is_empty(&self) -> bool { + self.seen_elements.is_empty() + } + fn intern(&mut self, cols: &[ArrayRef], groups: &mut Vec<usize>) -> Result<()> { + assert_eq!( + cols.len(), + 1, + "GroupValuesDictionary only supports a single column" + ); + let array = Arc::clone(&cols[0]); + groups.clear(); // zero out buffer + let dict_array = array + .as_dictionary_opt() + .map_or_else(|| Err(Internal("Expected dictionary array".into())), Ok)?; + + let values = dict_array.values(); + let key_array: &PrimitiveArray<K> = dict_array.keys(); + if key_array.is_empty() { + return Ok(()); + } + + let cache_hit = self + .values_cache + .0 + .as_ref() + .map(|cached| Arc::ptr_eq(cached, values)) + .unwrap_or(false); + + if !cache_hit { + // values array changed since last batch - recompute hashes and update cached pointer + self.compute_value_hashes(values)?; + self.values_cache.0 = Some(Arc::clone(values)); + } + let mut key_to_group: Vec<Option<usize>> = vec![None; values.len()]; + // For values already seen in prior batches, pre fill `key_to_group` + // so the main loop below can skip hash table lookups for those keys. + // This pre scan is skipped on the first batch since the hash table is empty. + if self.intern_called { + for i in 0..key_array.len() { + if key_array.is_null(i) { + continue; + } + let original_key = key_array.value(i).to_usize().unwrap(); + if values.is_null(original_key) { + continue; + } + if key_to_group[original_key].is_some() { + continue; + } + + let hash = self.values_cache.1[original_key]; + let raw = Self::get_raw_bytes(values, original_key); + if let Some(entry) = self + .unique_dict_value_mapping + .find(hash, |e| e.bytes == raw.as_ref()) + { + key_to_group[original_key] = Some(entry.group_id); + } + } + } + // iterate keys array (n iterations) + // only d insertions at most, repeated work is cached + for i in 0..key_array.len() { + let group_id = if key_array.is_null(i) { + self.get_null_group_id() + } else { + let key = key_array.value(i).to_usize().unwrap(); + if let Some(group_id) = key_to_group[key] { + group_id + } else if values.is_null(key) { + let gid = self.get_null_group_id(); + key_to_group[key] = Some(gid); + gid + } else { + let hash = self.values_cache.1[key]; + let raw = Self::get_raw_bytes(values, key); + let gid = self.lookup_or_insert_in_table(hash, raw.as_ref()); + key_to_group[key] = Some(gid); + gid + } + }; + groups.push(group_id); + } + // set flag to true to repeated calls to intern will pre-fill key_to_group cache + self.intern_called = true; + Ok(()) + } + fn emit(&mut self, emit_to: EmitTo) -> Result<Vec<ArrayRef>> { + let (elements_to_emit, null_id) = match emit_to { + EmitTo::All => { + let original_null_id = self.null_group_id; + self.null_group_id = None; + self.unique_dict_value_mapping.clear(); + (std::mem::take(&mut self.seen_elements), original_null_id) + } + EmitTo::First(n) => { + let n = n.min(self.seen_elements.len()); + let first_n = self.seen_elements.drain(..n).collect::<Vec<_>>(); // again read from raw buffer directly + let original_null_id = self.null_group_id.filter(|&id| id < n); + // update null_group_id if the null group was in the first n + if let Some(null_id) = self.null_group_id { + if null_id < n { + self.null_group_id = None; + } else { + self.null_group_id = Some(null_id - n); + } + } + // shift all remaining group indices down by n in the table + self.unique_dict_value_mapping.retain(|e| { + if e.group_id < n { + false + } else { + e.group_id -= n; + true + } + }); + (first_n, original_null_id) + } + }; + + let n = elements_to_emit.len(); + let values_array = self.transform_into_array(&elements_to_emit)?; // ingest a buffer + n then produce an array. should also update the len+offset of other entries #TODO see https://github.com/apache/datafusion/issues/22078 + + let mut keys_builder = PrimitiveBuilder::<K>::with_capacity(n); + if let Some(null_id) = null_id { + for i in 0..n { + if i == null_id { + keys_builder.append_null(); + } else { + keys_builder.append_value(K::Native::usize_as(i)); + } + } + } else { + for i in 0..n { + keys_builder.append_value(K::Native::usize_as(i)); + } Review Comment: Each chunk of data that flows in can carry its own lookup list of values. Small number types can only count so high, one of them maxes out at 256. But across many chunks, the total number of distinct groups can grow past that limit. When it does, the counter wraps around and starts over from zero, so a group near the end gets labeled with some other group's value. Before producing results, we should check whether the group count still fits in the number type if not, stop with a clear error. Even nicer would be automatically switching to a bigger number type? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
