Speed up uuid UDF (40x faster)

datafusion/functions/Cargo.toml

@@ -108,6 +108,11 @@ harness = false
 name = "encoding"
 required-features = ["encoding_expressions"]
 
+[[bench]]
+harness = false
+name = "uuid"
+required-features = ["string_expressions"]
+
 [[bench]]
 harness = false
 name = "regx"

datafusion/functions/benches/uuid.rs

@@ -0,0 +1,31 @@
+// 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.
+
+extern crate criterion;
+
+use criterion::{black_box, criterion_group, criterion_main, Criterion};
+use datafusion_functions::string;
+
+fn criterion_benchmark(c: &mut Criterion) {
+    let uuid = string::uuid();
+    c.bench_function("uuid", |b| {
+        b.iter(|| black_box(uuid.invoke_batch(&[], 1024)))
+    });
+}
+
+criterion_group!(benches, criterion_benchmark);
+criterion_main!(benches);

datafusion/functions/src/string/uuid.rs

@@ -18,9 +18,10 @@
 use std::any::Any;
 use std::sync::Arc;
 
-use arrow::array::GenericStringArray;
+use arrow::array::GenericStringBuilder;
 use arrow::datatypes::DataType;
 use arrow::datatypes::DataType::Utf8;
+use rand::Rng;
 use uuid::Uuid;
 
 use datafusion_common::{internal_err, Result};
@@ -87,9 +88,25 @@ impl ScalarUDFImpl for UuidFunc {
         if !args.is_empty() {
             return internal_err!("{} function does not accept arguments", self.name());
         }
-        let values = std::iter::repeat_with(|| Uuid::new_v4().to_string()).take(num_rows);
-        let array = GenericStringArray::<i32>::from_iter_values(values);
-        Ok(ColumnarValue::Array(Arc::new(array)))
+
+        // Generate random u128 values
+        let mut rng = rand::thread_rng();
+        let mut randoms = vec![0u128; num_rows];
+        rng.fill(&mut randoms[..]);
+
+        let mut builder =
+            GenericStringBuilder::<i32>::with_capacity(num_rows, num_rows * 36);
+
+        let mut buffer = [0u8; 36];
+        for x in &mut randoms {
+            // From Uuid::new_v4(): Mask out the version and variant bits
+            *x = *x & 0xFFFFFFFFFFFF4FFFBFFFFFFFFFFFFFFF | 0x40008000000000000000;
+            let uuid = Uuid::from_u128(*x);
+            let fmt = uuid::fmt::Hyphenated::from_uuid(uuid);
+            builder.append_value(fmt.encode_lower(&mut buffer));
+        }
+
+        Ok(ColumnarValue::Array(Arc::new(builder.finish())))
     }
 
     fn documentation(&self) -> Option<&Documentation> {

datafusion/sqllogictest/test_files/functions.slt

@@ -720,6 +720,14 @@ select count(distinct u) from uuid_table;
 ----
 2
 
+# must be valid uuidv4 format
+query B
+SELECT REGEXP_LIKE(uuid(),
+       '^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$')
+       AS is_valid;
+----
+true
+
 statement ok
 drop table uuid_table