Add benchmarks for dictionary path of new_group_values (#22004)

## Which issue does this PR close?
benchmarks for #21765. Also related to #21860 
The goal is to merge this PR and then rebase the branch on #21765 to
contain these benchmarks, so that they can be run and compared to the
original.
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## Rationale for this change
Originally this was included in #21765 but that PR is already very
large. I decided to move it to its own separate PR
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in the issue then this section is not needed.
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## What changes are included in this PR?
Adds benchmarks for the dictionary encoding array path of
**new_group_values()**.
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## Are these changes tested?
n/a
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## Are there any user-facing changes?
no
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---------

Co-authored-by: Kumar Ujjawal <ujjawalpathak6@gmail.com>

Author: Rich-T-kid

datafusion/physical-plan/Cargo.toml

@@ -112,3 +112,7 @@ required-features = ["test_utils"]
 harness = false
 name = "aggregate_vectorized"
 required-features = ["test_utils"]
+
+[[bench]]
+harness = false
+name = "dictionary_group_values"

datafusion/physical-plan/benches/dictionary_group_values.rs

@@ -0,0 +1,176 @@
+// 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.
+
+//! Benchmarks for `GroupValues` over a single `Dictionary<Int32, Utf8>`
+//! column. Each iteration measures `intern` (once or N times) followed by
+//! `emit(EmitTo::All)`. The `Box<dyn GroupValues>` returned by
+//! `new_group_values` is constructed in the setup closure of
+//! `iter_batched_ref` and is not included in the timing.
+
+use arrow::array::{ArrayRef, DictionaryArray, PrimitiveArray, StringArray};
+use arrow::buffer::{Buffer, NullBuffer};
+use arrow::datatypes::{DataType, Field, Int32Type, Schema, SchemaRef};
+use criterion::{
+    BatchSize, BenchmarkId, Criterion, Throughput, criterion_group, criterion_main,
+};
+use datafusion_expr::EmitTo;
+use datafusion_physical_plan::aggregates::group_values::new_group_values;
+use datafusion_physical_plan::aggregates::order::GroupOrdering;
+use rand::rngs::StdRng;
+use rand::seq::SliceRandom;
+use rand::{Rng, SeedableRng};
+use std::hint::black_box;
+use std::sync::Arc;
+
+const SIZES: [usize; 2] = [8 * 1024, 64 * 1024];
+const CARDS_RELATIVE: [usize; 4] = [20, 75, 300, 1000];
+const N_BATCHES: usize = 4;
+// Fixed for reproducibility.
+const SEED: u64 = 0xD1C7;
+
+fn dict_schema() -> SchemaRef {
+    let dict_ty =
+        DataType::Dictionary(Box::new(DataType::Int32), Box::new(DataType::Utf8));
+    Arc::new(Schema::new(vec![Field::new("g", dict_ty, true)]))
+}
+
+/// Build a `Dictionary<Int32, Utf8>` column.
+fn make_dict(size: usize, cardinality: usize, null_density: f32, seed: u64) -> ArrayRef {
+    let strings: Vec<String> = (0..cardinality).map(|i| format!("v_{i:08}")).collect();
+    let values = Arc::new(StringArray::from(
+        strings.iter().map(String::as_str).collect::<Vec<_>>(),
+    ));
+
+    let mut rng = StdRng::seed_from_u64(seed);
+    let keys: Vec<i32> = if cardinality == size {
+        let mut perm: Vec<i32> = (0..size as i32).collect();
+        perm.shuffle(&mut rng);
+        perm
+    } else {
+        (0..size)
+            .map(|_| rng.random_range(0..cardinality) as i32)
+            .collect()
+    };
+    let keys_buf = Buffer::from_slice_ref(&keys);
+
+    let nulls: Option<NullBuffer> = (null_density > 0.0).then(|| {
+        (0..size)
+            .map(|_| !rng.random_bool(null_density as f64))
+            .collect()
+    });
+
+    let key_array = PrimitiveArray::<Int32Type>::new(keys_buf.into(), nulls);
+    Arc::new(DictionaryArray::<Int32Type>::try_new(key_array, values).unwrap())
+}
+
+fn bench_id(
+    label: &str,
+    size: usize,
+    cardinality: usize,
+    null_density: f32,
+) -> BenchmarkId {
+    BenchmarkId::new(
+        label,
+        format!("size_{size}_card_{cardinality}_null_{null_density:.2}"),
+    )
+}
+
+fn bench_intern_emit(c: &mut Criterion) {
+    let mut group = c.benchmark_group("dict_intern_emit");
+    let schema = dict_schema();
+    let null_density = 0.0;
+
+    for &size in &SIZES {
+        let mut cards = CARDS_RELATIVE.to_vec();
+        cards.push(size); // all-unique stress case
+        for cardinality in cards {
+            let array = make_dict(size, cardinality, null_density, SEED);
+            group.throughput(Throughput::Elements(size as u64));
+            group.bench_function(
+                bench_id("intern_emit", size, cardinality, null_density),
+                |b| {
+                    b.iter_batched_ref(
+                        || {
+                            (
+                                new_group_values(schema.clone(), &GroupOrdering::None)
+                                    .unwrap(),
+                                Vec::<usize>::with_capacity(size),
+                            )
+                        },
+                        |(gv, groups)| {
+                            gv.intern(std::slice::from_ref(&array), groups).unwrap();
+                            black_box(&*groups);
+                            black_box(gv.emit(EmitTo::All).unwrap());
+                        },
+                        BatchSize::SmallInput,
+                    );
+                },
+            );
+        }
+    }
+    group.finish();
+}
+
+fn bench_repeated_intern_emit(c: &mut Criterion) {
+    let mut group = c.benchmark_group("dict_repeated_intern_emit");
+    let schema = dict_schema();
+    let null_density = 0.10;
+
+    for &size in &SIZES {
+        let mut cards = CARDS_RELATIVE.to_vec();
+        cards.push(size);
+        for cardinality in cards {
+            let batches: Vec<ArrayRef> = (0..N_BATCHES)
+                .map(|i| {
+                    make_dict(
+                        size,
+                        cardinality,
+                        null_density,
+                        SEED.wrapping_add(i as u64),
+                    )
+                })
+                .collect();
+            group.throughput(Throughput::Elements((size * N_BATCHES) as u64));
+            group.bench_function(
+                bench_id("repeated_intern_emit", size, cardinality, null_density),
+                |b| {
+                    b.iter_batched_ref(
+                        || {
+                            (
+                                new_group_values(schema.clone(), &GroupOrdering::None)
+                                    .unwrap(),
+                                Vec::<usize>::with_capacity(size),
+                            )
+                        },
+                        |(gv, groups)| {
+                            for arr in &batches {
+                                gv.intern(std::slice::from_ref(arr), groups).unwrap();
+                                black_box(&*groups);
+                            }
+                            black_box(gv.emit(EmitTo::All).unwrap());
+                        },
+                        BatchSize::SmallInput,
+                    );
+                },
+            );
+        }
+    }
+    group.finish();
+}
+
+criterion_group!(benches, bench_intern_emit, bench_repeated_intern_emit);
+criterion_main!(benches);