[BugFix] Use a separate thread pool for dictionary collection (backport

StarRocks#54454) (StarRocks#54511)

Co-authored-by: stdpain <[email protected]>

fe/fe-core/src/main/java/com/starrocks/common/Config.java

@@ -2146,6 +2146,9 @@ public class Config extends ConfigBase {
     @ConfField
     public static long statistic_dict_columns = 100000;
 
+    @ConfField
+    public static int dict_collect_thread_pool_size = 16;
+
     /**
      * The column statistic cache update interval
      */

fe/fe-core/src/main/java/com/starrocks/sql/optimizer/statistics/CacheDictManager.java

@@ -25,6 +25,7 @@
 import com.starrocks.common.Config;
 import com.starrocks.common.Pair;
 import com.starrocks.common.Status;
+import com.starrocks.common.ThreadPoolManager;
 import com.starrocks.memory.MemoryTrackable;
 import com.starrocks.qe.ConnectContext;
 import com.starrocks.server.GlobalStateMgr;
@@ -54,7 +55,7 @@ public class CacheDictManager implements IDictManager, MemoryTrackable {
 
     public static final Integer LOW_CARDINALITY_THRESHOLD = 255;
 
-    private CacheDictManager() {
+    public CacheDictManager() {
     }
 
     private static final CacheDictManager INSTANCE = new CacheDictManager();
@@ -107,6 +108,8 @@ public CompletableFuture<Optional<ColumnDict>> asyncReload(
 
     private final AsyncLoadingCache<ColumnIdentifier, Optional<ColumnDict>> dictStatistics = Caffeine.newBuilder()
             .maximumSize(Config.statistic_dict_columns)
+            .executor(ThreadPoolManager.newDaemonCacheThreadPool(Config.dict_collect_thread_pool_size, "cache-dict",
+                    false))
             .buildAsync(dictLoader);
 
     private Optional<ColumnDict> deserializeColumnDict(long tableId, ColumnId columnName, TStatisticData statisticData) {

fe/fe-core/src/test/java/com/starrocks/catalog/CacheDictManagerTest.java

@@ -0,0 +1,35 @@
+// Copyright 2021-present StarRocks, Inc. All rights reserved.
+//
+// Licensed 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
+//
+//     https://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 com.starrocks.catalog;
+
+import com.starrocks.sql.optimizer.statistics.CacheDictManager;
+import mockit.Expectations;
+import org.junit.Test;
+
+import java.util.Optional;
+
+public class CacheDictManagerTest {
+    @Test
+    public void test() {
+        CacheDictManager manager = new CacheDictManager();
+        new Expectations(manager) {
+            {
+                manager.getGlobalDict(anyLong, ColumnId.create("val"));
+                result = Optional.empty();
+            }
+        };
+        manager.getGlobalDict(1, ColumnId.create("val"));
+    }
+}