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// 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.
//! [`Partitioning`] and [`Distribution`] for physical expressions
use std::fmt;
use std::sync::Arc;
use crate::{
expr_list_eq_strict_order, normalize_expr_with_equivalence_properties,
EquivalenceProperties, PhysicalExpr,
};
/// Partitioning schemes supported by operators.
#[derive(Debug, Clone)]
pub enum Partitioning {
/// Allocate batches using a round-robin algorithm and the specified number of partitions
RoundRobinBatch(usize),
/// Allocate rows based on a hash of one of more expressions and the specified number of
/// partitions
Hash(Vec<Arc<dyn PhysicalExpr>>, usize),
/// Unknown partitioning scheme with a known number of partitions
UnknownPartitioning(usize),
}
impl fmt::Display for Partitioning {
fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
match self {
Partitioning::RoundRobinBatch(size) => write!(f, "RoundRobinBatch({size})"),
Partitioning::Hash(phy_exprs, size) => {
let phy_exprs_str = phy_exprs
.iter()
.map(|e| format!("{e}"))
.collect::<Vec<String>>()
.join(", ");
write!(f, "Hash([{phy_exprs_str}], {size})")
}
Partitioning::UnknownPartitioning(size) => {
write!(f, "UnknownPartitioning({size})")
}
}
}
}
impl Partitioning {
/// Returns the number of partitions in this partitioning scheme
pub fn partition_count(&self) -> usize {
use Partitioning::*;
match self {
RoundRobinBatch(n) | Hash(_, n) | UnknownPartitioning(n) => *n,
}
}
/// Returns true when the guarantees made by this [[Partitioning]] are sufficient to
/// satisfy the partitioning scheme mandated by the `required` [[Distribution]]
pub fn satisfy<F: FnOnce() -> EquivalenceProperties>(
&self,
required: Distribution,
equal_properties: F,
) -> bool {
match required {
Distribution::UnspecifiedDistribution => true,
Distribution::SinglePartition if self.partition_count() == 1 => true,
Distribution::HashPartitioned(required_exprs) => {
match self {
// Here we do not check the partition count for hash partitioning and assumes the partition count
// and hash functions in the system are the same. In future if we plan to support storage partition-wise joins,
// then we need to have the partition count and hash functions validation.
Partitioning::Hash(partition_exprs, _) => {
let fast_match =
expr_list_eq_strict_order(&required_exprs, partition_exprs);
// If the required exprs do not match, need to leverage the eq_properties provided by the child
// and normalize both exprs based on the eq_properties
if !fast_match {
let eq_properties = equal_properties();
let eq_classes = eq_properties.classes();
if !eq_classes.is_empty() {
let normalized_required_exprs = required_exprs
.iter()
.map(|e| {
normalize_expr_with_equivalence_properties(
e.clone(),
eq_classes,
)
})
.collect::<Vec<_>>();
let normalized_partition_exprs = partition_exprs
.iter()
.map(|e| {
normalize_expr_with_equivalence_properties(
e.clone(),
eq_classes,
)
})
.collect::<Vec<_>>();
expr_list_eq_strict_order(
&normalized_required_exprs,
&normalized_partition_exprs,
)
} else {
fast_match
}
} else {
fast_match
}
}
_ => false,
}
}
_ => false,
}
}
}
impl PartialEq for Partitioning {
fn eq(&self, other: &Partitioning) -> bool {
match (self, other) {
(
Partitioning::RoundRobinBatch(count1),
Partitioning::RoundRobinBatch(count2),
) if count1 == count2 => true,
(Partitioning::Hash(exprs1, count1), Partitioning::Hash(exprs2, count2))
if expr_list_eq_strict_order(exprs1, exprs2) && (count1 == count2) =>
{
true
}
_ => false,
}
}
}
/// Distribution schemes
#[derive(Debug, Clone)]
pub enum Distribution {
/// Unspecified distribution
UnspecifiedDistribution,
/// A single partition is required
SinglePartition,
/// Requires children to be distributed in such a way that the same
/// values of the keys end up in the same partition
HashPartitioned(Vec<Arc<dyn PhysicalExpr>>),
}
impl Distribution {
/// Creates a Partitioning for this Distribution to satisfy itself
pub fn create_partitioning(&self, partition_count: usize) -> Partitioning {
match self {
Distribution::UnspecifiedDistribution => {
Partitioning::UnknownPartitioning(partition_count)
}
Distribution::SinglePartition => Partitioning::UnknownPartitioning(1),
Distribution::HashPartitioned(expr) => {
Partitioning::Hash(expr.clone(), partition_count)
}
}
}
}