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 java.util.Collections;
  import java.util.List;
  
  import org.apache.asterix.om.typecomputer.base.TypeCastUtils;
  import org.apache.asterix.om.types.IAType;
  import org.apache.asterix.optimizer.rules.typecast.StaticTypeCastUtil;
  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.expressions.AbstractFunctionCallExpression;
  import org.apache.hyracks.algebricks.core.algebra.expressions.IVariableTypeEnvironment;
  import org.apache.hyracks.algebricks.core.algebra.operators.logical.AbstractAssignOperator;
  import org.apache.hyracks.algebricks.core.algebra.operators.logical.AbstractLogicalOperator;
  import org.apache.hyracks.algebricks.core.algebra.operators.logical.AbstractUnnestOperator;
  import org.apache.hyracks.algebricks.core.rewriter.base.IAlgebraicRewriteRule;
  
  /**
   * This class is to enforce types for function expressions which contain list constructor function calls.
   * The List constructor is very special because a nested list is of type List<ANY>.
   * However, the bottom-up type inference (InferTypeRule in algebricks) did not infer that so we need this method to enforce the type.
   * We do not want to break the generality of algebricks so this method is called in an ASTERIX rule: @ IntroduceEnforcedListTypeRule} .
   */
  public class IntroduceEnforcedListTypeRule 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 {
          if (context.checkIfInDontApplySet(this, opRef.getValue()))
              return false;
          AbstractLogicalOperator op = (AbstractLogicalOperator) opRef.getValue();
          context.addToDontApplySet(this, opRef.getValue());
  
          /**
           * rewrite list constructor types for list constructor functions
           */
          List<Mutable<ILogicalExpression>> expressions;
          // TODO(ali): what about other operators that could have list expressions?
          switch (op.getOperatorTag()) {
              case ASSIGN:
                  AbstractAssignOperator assignOp = (AbstractAssignOperator) op;
                  expressions = assignOp.getExpressions();
                  break;
              case UNNEST:
                  AbstractUnnestOperator unnestOp = (AbstractUnnestOperator) op;
                  expressions = Collections.singletonList(unnestOp.getExpressionRef());
                  break;
              default:
                  return false;
          }
          IVariableTypeEnvironment env = op.computeOutputTypeEnvironment(context);
          return rewriteExpressions(expressions, env);
      }
  
      private boolean rewriteExpressions(List<Mutable<ILogicalExpression>> expressions, IVariableTypeEnvironment env)
              throws AlgebricksException {
          boolean changed = false;
          for (Mutable<ILogicalExpression> exprRef : expressions) {
              ILogicalExpression expr = exprRef.getValue();
              if (expr.getExpressionTag() == LogicalExpressionTag.FUNCTION_CALL) {
                  AbstractFunctionCallExpression argFuncExpr = (AbstractFunctionCallExpression) expr;
                  IAType exprType = (IAType) env.getType(argFuncExpr);
                  if (StaticTypeCastUtil.rewriteListExpr(argFuncExpr, exprType, exprType, env)) {
                      TypeCastUtils.resetRequiredAndInputTypes(argFuncExpr);
                      changed = true;
                  }
              }
          }
          return changed;
      }
  
  }
  