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Subject [GitHub] [flink] twalthr commented on a change in pull request #8062: [FLINK-11884][table] Implement expression resolution on top of new Expressions
Date Mon, 08 Apr 2019 16:19:50 GMT
twalthr commented on a change in pull request #8062:  [FLINK-11884][table] Implement expression
resolution on top of new Expressions
URL: https://github.com/apache/flink/pull/8062#discussion_r273070489
 
 

 ##########
 File path: flink-table/flink-table-planner/src/main/java/org/apache/flink/table/expressions/rules/OverWindowResolverRule.java
 ##########
 @@ -0,0 +1,105 @@
+/*
+ * 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.expressions.rules;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.table.api.ValidationException;
+import org.apache.flink.table.expressions.ApiExpressionDefaultVisitor;
+import org.apache.flink.table.expressions.BuiltInFunctionDefinitions;
+import org.apache.flink.table.expressions.CallExpression;
+import org.apache.flink.table.expressions.CurrentRange;
+import org.apache.flink.table.expressions.CurrentRow;
+import org.apache.flink.table.expressions.Expression;
+import org.apache.flink.table.expressions.PlannerExpression;
+import org.apache.flink.table.plan.logical.LogicalOverWindow;
+import org.apache.flink.table.typeutils.RowIntervalTypeInfo;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import static java.util.Arrays.asList;
+import static java.util.stream.Collectors.toList;
+
+/**
+ * Joins call to {@link BuiltInFunctionDefinitions#OVER} with corresponding over window
+ * and creates a fully resolved over aggregation.
+ */
+@Internal
+final class OverWindowResolverRule implements ResolverRule {
+
+	@Override
+	public List<Expression> apply(List<Expression> expression, ResolutionContext
context) {
+		return expression.stream()
+			.map(expr -> expr.accept(new ExpressionResolverVisitor(context)))
+			.collect(Collectors.toList());
+	}
+
+	private class ExpressionResolverVisitor extends ApiExpressionDefaultVisitor<Expression>
{
+
+		private final ResolutionContext context;
+
+		ExpressionResolverVisitor(ResolutionContext context) {
+			this.context = context;
+		}
+
+		@Override
+		public Expression visitCall(CallExpression call) {
+
+			if (call.getFunctionDefinition() == BuiltInFunctionDefinitions.OVER) {
+				List<Expression> children = call.getChildren();
+				Expression alias = children.get(1);
+
+				LogicalOverWindow referenceWindow = context.getOverWindow(alias)
+					.orElseThrow(() -> new ValidationException("Could not resolve over call."));
+
+				Expression following = calculateOverWindowFollowing(referenceWindow);
+				List<Expression> newArgs = new ArrayList<>(asList(
+					children.get(0),
+					referenceWindow.orderBy(),
+					referenceWindow.preceding(),
+					following));
+
+				newArgs.addAll(referenceWindow.partitionBy());
+				return new CallExpression(call.getFunctionDefinition(), newArgs);
+			} else {
+				return new CallExpression(
+					call.getFunctionDefinition(),
+					call.getChildren().stream().map(expr -> expr.accept(this)).collect(toList()));
+			}
+		}
+
+		private Expression calculateOverWindowFollowing(LogicalOverWindow referenceWindow) {
+			return referenceWindow.following().orElseGet(() -> {
+					PlannerExpression preceding = context.bridge(referenceWindow.preceding());
+					if (preceding.resultType() instanceof RowIntervalTypeInfo) {
+						return new CurrentRow();
 
 Review comment:
   Change to a call instead of planner expressions.

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