[GitHub] [flink] godfreyhe commented on a change in pull request #8585: [FLINK-12690][table-api] Introduce a Planner interface

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godfreyhe commented on a change in pull request #8585:  [FLINK-12690][table-api] Introduce a Planner interface 
URL: https://github.com/apache/flink/pull/8585#discussion_r289703696
 
 

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 File path: flink-table/flink-table-api-java/src/main/java/org/apache/flink/table/planner/Planner.java
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+/*
+ * 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.table.planner;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.streaming.api.transformations.StreamTransformation;
+import org.apache.flink.table.operations.ModifyOperation;
+import org.apache.flink.table.operations.QueryOperation;
+import org.apache.flink.table.operations.TableOperation;
+
+import java.util.List;
+
+/**
+ * This interface serves two purposes:
+ * <ul>
+ * <li>SQL parser - transforms a SQL string into a Table API specific tree of
+ * {@link TableOperation}s</li>
+ * <li>relational planner - provides a way to plan, optimize and transform tree of
+ * {@link ModifyOperation} into a runnable form ({@link StreamTransformation})</li>
+ * </ul>.
+ *
+ * <p>The Planner is execution agnostic. It is up to the
+ * {@link org.apache.flink.table.api.TableEnvironment} to ensure that if any of the
+ * {@link QueryOperation} pull any runtime configuration, all those configurations are
+ * equivalent. Example: If some of the {@link QueryOperation}s scan DataStreams, all
+ * those DataStreams must come from the same StreamExecutionEnvironment, because the result
+ * of {@link Planner#translate(List)} will strip any execution configuration from
+ * the DataStream information.
+ *
+ * <p>All Tables referenced in either {@link Planner#parse(String)} or
+ * {@link Planner#translate(List)} should be previously registered in a
+ * {@link org.apache.flink.table.catalog.CatalogManager}, which will be provided during
+ * instantiation of the {@link Planner}.
+ */
+@Internal
+public interface Planner {
+
+	/**
+	 * Entry point for parsing sql queries expressed as a String.
+	 *
+	 * <p><b>Note:</b>If the created {@link TableOperation} is a {@link QueryOperation}
+	 * it must be in a form that will be understood by the
+	 * {@link Planner#translate(List)} method.
+	 *
+	 * <p>The produced Operation tree should already be validated.
+	 *
+	 * @param stmt the sql statement to evaluate
+	 * @return parsed query as a tree of relational {@link TableOperation}s
+	 */
+	TableOperation parse(String stmt);
+
+	/**
+	 * Converts a relational tree of {@link QueryOperation}s into a set of runnable
+	 * {@link StreamTransformation}s.
+	 *
+	 * <p>This method accepts a list of {@link QueryOperation}s to allow reusing common
+	 * subtrees of multiple relational queries.
+	 *
+	 * @param tableOperations list of relational operations to plan, optimize and convert in a
+	 * single run.
+	 * @return list of corresponding {@link StreamTransformation}s.
+	 */
+	List<StreamTransformation<?>> translate(List<ModifyOperation> tableOperations);
 
 Review comment:
   the argument and the comments are inconsistent: the argument is a list of `ModifyOperation`, while the comments describe a list of `QueryOperation`. 
   
   btw, if this method accepts a list of `ModifyOperation`, do we need implicitly add sink or output conversion for plan test queries? like queries in `CalcTest`

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