content: /*
   * 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.asterix.optimizer.rules;
  
  import org.apache.asterix.om.functions.BuiltinFunctions;
  import org.apache.asterix.om.functions.IFunctionToDataSourceRewriter;
  import org.apache.commons.lang3.mutable.Mutable;
  import org.apache.hyracks.algebricks.common.exceptions.AlgebricksException;
  import org.apache.hyracks.algebricks.core.algebra.base.ILogicalExpression;
  import org.apache.hyracks.algebricks.core.algebra.base.ILogicalOperator;
  import org.apache.hyracks.algebricks.core.algebra.base.IOptimizationContext;
  import org.apache.hyracks.algebricks.core.algebra.base.LogicalExpressionTag;
  import org.apache.hyracks.algebricks.core.algebra.base.LogicalOperatorTag;
  import org.apache.hyracks.algebricks.core.algebra.expressions.AbstractFunctionCallExpression;
  import org.apache.hyracks.algebricks.core.algebra.operators.logical.AbstractLogicalOperator;
  import org.apache.hyracks.algebricks.core.algebra.operators.logical.UnnestOperator;
  import org.apache.hyracks.algebricks.core.rewriter.base.IAlgebraicRewriteRule;
  
  public class UnnestToDataScanRule implements IAlgebraicRewriteRule {
  
      @Override
      public boolean rewritePre(Mutable<ILogicalOperator> opRef, IOptimizationContext context)
              throws AlgebricksException {
          return false;
      }
  
      @Override
      public boolean rewritePost(Mutable<ILogicalOperator> opRef, IOptimizationContext context)
              throws AlgebricksException {
          AbstractFunctionCallExpression f = getFunctionCall(opRef);
          if (f == null) {
              return false;
          }
          IFunctionToDataSourceRewriter transformer =
                  BuiltinFunctions.getDatasourceTransformer(f.getFunctionIdentifier());
          if (transformer == null) {
              return false;
          }
          return transformer.rewrite(opRef, context);
      }
  
      public static AbstractFunctionCallExpression getFunctionCall(Mutable<ILogicalOperator> opRef) {
          AbstractLogicalOperator op = (AbstractLogicalOperator) opRef.getValue();
          if (op.getOperatorTag() != LogicalOperatorTag.UNNEST) {
              return null;
          }
          UnnestOperator unnest = (UnnestOperator) op;
          ILogicalExpression unnestExpr = unnest.getExpressionRef().getValue();
          if (unnestExpr.getExpressionTag() != LogicalExpressionTag.FUNCTION_CALL) {
              return null;
          }
          return (AbstractFunctionCallExpression) unnestExpr;
      }
  
  }
  