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Subject [GitHub] [flink] danny0405 commented on a change in pull request #8859: [FLINK-12905][table-planner] Enable querying CatalogViews in legacy planner
Date Wed, 27 Nov 2019 02:31:39 GMT
danny0405 commented on a change in pull request #8859: [FLINK-12905][table-planner] Enable
querying CatalogViews in legacy planner
URL: https://github.com/apache/flink/pull/8859#discussion_r351070890
 
 

 ##########
 File path: flink-table/flink-table-planner-blink/src/main/java/org/apache/flink/table/planner/catalog/SqlCatalogViewTable.java
 ##########
 @@ -0,0 +1,61 @@
+/*
+ * 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.catalog;
+
+import org.apache.flink.table.catalog.CatalogView;
+import org.apache.flink.table.planner.plan.schema.ExpandingPreparingTable;
+import org.apache.flink.table.planner.plan.stats.FlinkStatistic;
+
+import org.apache.calcite.plan.RelOptSchema;
+import org.apache.calcite.plan.RelOptUtil;
+import org.apache.calcite.rel.RelNode;
+import org.apache.calcite.rel.RelRoot;
+import org.apache.calcite.rel.type.RelDataType;
+
+import javax.annotation.Nullable;
+
+import java.util.List;
+
+/**
+ * A bridge between a Flink's specific {@link CatalogView} and a Calcite's
+ * {@link org.apache.calcite.plan.RelOptTable}. It implements parsing and conversion from
sql string to
+ * {@link org.apache.calcite.rel.RelNode}.
+ */
+public class SqlCatalogViewTable extends ExpandingPreparingTable {
+	private final CatalogView view;
+	private final List<String> viewPath;
+
+	public SqlCatalogViewTable(
+			@Nullable RelOptSchema relOptSchema,
+			RelDataType rowType,
+			Iterable<String> names,
+			FlinkStatistic statistic,
+			CatalogView view,
+			List<String> viewPath) {
+		super(relOptSchema, rowType, names, statistic);
+		this.view = view;
+		this.viewPath = viewPath;
+	}
+
+	@Override
+	public RelNode expandTopLevel(ToRelContext context) {
+		RelRoot root = context.expandView(rowType, view.getExpandedQuery(), viewPath, names);
+		return RelOptUtil.createCastRel(root.rel, rowType, true);
+	}
 
 Review comment:
   The only reason i can see is to fix the nullability, or rename the node (e.g. create view
with column alias), for the nullability, we should fix it from the source, we do not support
the view alias yet, so there is no need to add the casts.

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