Jiabao-Sun commented on code in PR #1:
URL: 
https://github.com/apache/flink-connector-mongodb/pull/1#discussion_r1035041422


##########
flink-connector-mongodb/src/main/java/org/apache/flink/connector/mongodb/source/enumerator/splitter/MongoSplitters.java:
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@@ -0,0 +1,110 @@
+/*
+ * 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.
+ */
+
+package org.apache.flink.connector.mongodb.source.enumerator.splitter;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.connector.mongodb.common.config.MongoConnectionOptions;
+import org.apache.flink.connector.mongodb.common.utils.MongoUtils;
+import org.apache.flink.connector.mongodb.source.config.MongoReadOptions;
+import org.apache.flink.connector.mongodb.source.split.MongoScanSourceSplit;
+import org.apache.flink.connector.mongodb.source.split.MongoSourceSplit;
+
+import com.mongodb.MongoNamespace;
+import com.mongodb.client.MongoClient;
+import com.mongodb.client.MongoClients;
+import org.bson.BsonDocument;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.Closeable;
+import java.io.IOException;
+import java.io.Serializable;
+import java.util.Collection;
+
+import static 
org.apache.flink.connector.mongodb.common.utils.MongoConstants.ERROR_MESSAGE_FIELD;
+import static 
org.apache.flink.connector.mongodb.common.utils.MongoUtils.isCommandSucceed;
+
+/** To split collections of MongoDB to {@link MongoSourceSplit}s. */
+@Internal
+public class MongoSplitters implements Serializable, Closeable {
+
+    private static final long serialVersionUID = 1L;
+
+    private static final Logger LOG = 
LoggerFactory.getLogger(MongoSplitters.class);
+
+    private final MongoReadOptions readOptions;
+    private final boolean limitPushedDown;
+    private final MongoClient mongoClient;
+
+    public MongoSplitters(
+            MongoConnectionOptions connectionOptions,
+            MongoReadOptions readOptions,
+            boolean limitPushedDown) {
+        this.readOptions = readOptions;
+        this.limitPushedDown = limitPushedDown;
+        this.mongoClient = MongoClients.create(connectionOptions.getUri());
+    }
+
+    public Collection<MongoScanSourceSplit> split(MongoNamespace namespace) {
+        BsonDocument collStats = MongoUtils.collStats(mongoClient, namespace);
+        if (!isCommandSucceed(collStats)) {
+            LOG.error(
+                    "Execute command collStats failed: {}",
+                    collStats.getString(ERROR_MESSAGE_FIELD));
+            throw new IllegalStateException(String.format("Collection not 
found %s", namespace));
+        }
+
+        MongoSplitContext splitContext =
+                MongoSplitContext.of(readOptions, mongoClient, namespace, 
collStats);
+
+        if (limitPushedDown) {
+            LOG.info("Limit {} is applied, using single splitter", 
limitPushedDown);
+            return MongoSingleSplitter.INSTANCE.split(splitContext);
+        }

Review Comment:
   @zentol 
   I made some test for that case, the `Table` runtime indeed deal with the 
rest but the `DataStream` runtime seems not. 
   Is it necessary to allow limits under the `DataStream` API as well ?
   If necessary, where would it be appropriate to deal with the rest, maybe 
`RecordEmitter` ?



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