[GitHub] [flink] aljoscha commented on a change in pull request #8695: [FLINK-12805][FLINK-12808][FLINK-12809][table-api] Introduce PartitionableTableSource and PartitionableTableSink and OverwritableTableSink

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aljoscha commented on a change in pull request #8695: [FLINK-12805][FLINK-12808][FLINK-12809][table-api] Introduce PartitionableTableSource and PartitionableTableSink and OverwritableTableSink
URL: https://github.com/apache/flink/pull/8695#discussion_r298952675
 
 

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 File path: flink-table/flink-table-common/src/main/java/org/apache/flink/table/sinks/PartitionableTableSink.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.sinks;
+
+import org.apache.flink.annotation.Experimental;
+
+import java.util.List;
+import java.util.Map;
+
+/**
+ * An interface for partitionable {@link TableSink}. A partitionable sink can writes
+ * query results to partitions.
+ *
+ * <p>Partition columns are defined via {@link #getPartitionFieldNames()} and the field names
+ * should be sorted in a strict order. And all the partition fields should exist in the
+ * {@link TableSink#getTableSchema()}.
+ *
+ * <p>For example, a partitioned table named {@code my_table} with a table schema
+ * {@code [a INT, b VARCHAR, c DOUBLE, dt VARCHAR, country VARCHAR]} is partitioned on columns
+ * {@code dt, country}. Then {@code dt} is the first partition column, and
+ * {@code country} is the secondary partition column.
+ *
+ * <p>We can insert data into table partitions using INSERT INTO PARTITION syntax, for example:
+ * <pre>
+ * <code>
+ *     INSERT INTO my_table PARTITION (dt='2019-06-20', country='bar') select a, b, c from my_view
+ * </code>
+ * </pre>
+ * When all the partition columns are set a value in PARTITION clause, it is inserting into a
+ * static partition. It will writes the query result into a static partition,
+ * i.e. {@code dt='2019-06-20', country='bar'}. The user specified static partitions will be told
+ * to the sink via {@link #setStaticPartition(Map)}.
+ *
+ * <p>The INSERT INTO PARTITION syntax also supports dynamic partition inserts.
+ * <pre>
+ * <code>
+ *     INSERT INTO my_table PARTITION (dt='2019-06-20') select a, b, c, country from another_view
+ * </code>
+ * </pre>
+ * When partial partition columns (prefix part of all partition columns) are set a value in
+ * PARTITION clause, it is writing the query result into a dynamic partition. In the above example,
+ * the static partition part is {@code dt='2019-06-20'} which will be told to the sink via
+ * {@link #setStaticPartition(Map)}. And the {@code country} is the dynamic partition which will be
+ * get from each record.
+ */
+@Experimental
+public interface PartitionableTableSink {
+
+	/**
+	 * Gets the partition field names of the table. The partition field names should be sorted in
+	 * a strict order, i.e. they have the order as specified in the PARTITION statement in DDL.
+	 * This should be an empty set if the table is not partitioned.
+	 *
+	 * <p>All the partition fields should exist in the {@link TableSink#getTableSchema()}.
+	 *
+	 * @return partition field names of the table, empty if the table is not partitioned.
+	 */
+	List<String> getPartitionFieldNames();
+
+	/**
+	 * Sets the static partition into the {@link TableSink}. The static partition may be partial
+	 * of all partition columns. See the class Javadoc for more details.
+	 *
+	 * <p>The static partition is represented as a {@code Map<String, String>} which maps from
+	 * partition field name to partition value. The partition values are all encoded as strings,
+	 * i.e. encoded using String.valueOf(...). For example, there is a static partition
 
 Review comment:
   ```suggestion
   	 * i.e. encoded using String.valueOf(...). For example, if we have static partitions
   ```

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