feat:add pool to init once

pkg/util/distance/calc_distance.go

@@ -155,8 +155,7 @@ func CalcFloatDistance(dim int64, left, right []float32, metric string) ([]float
 		waitGroup.Done()
 	}
 	// avoid too many goroutines by ants pool
-	pool := conc.NewDefaultPool[any]()
-	defer pool.Release()
+	pool := GetCalcPool()
 	for i := int64(0); i < leftNum; i++ {
 		waitGroup.Add(1)
 		index := i

pkg/util/distance/pool.go

@@ -0,0 +1,31 @@
+// Licensed to the LF AI & Data foundation 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.
+
+package distance
+
+var (
+	calcPool         *conc.Pool[any]
+	calcPoolInitOnce = new(sync.Once)
+)
+
+func initCalcPool() {
+	calcPool = conc.NewDefaultPool[any]()
+}
+
+func GetCalcPool() *conc.Pool[any] {
+	calcPoolInitOnce.Do(initCalcPool)
+	return calcPool
+}