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.ArrayList;
  import java.util.Collections;
  
  import org.apache.asterix.algebra.base.OperatorAnnotation;
  import org.apache.asterix.om.base.AInt32;
  import org.apache.asterix.om.constants.AsterixConstantValue;
  import org.apache.asterix.om.functions.BuiltinFunctions;
  import org.apache.asterix.om.typecomputer.impl.TypeComputeUtils;
  import org.apache.asterix.om.types.ARecordType;
  import org.apache.asterix.om.types.ATypeTag;
  import org.apache.asterix.om.types.IAType;
  import org.apache.asterix.om.utils.ConstantExpressionUtil;
  import org.apache.commons.lang3.mutable.Mutable;
  import org.apache.commons.lang3.mutable.MutableObject;
  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.LogicalVariable;
  import org.apache.hyracks.algebricks.core.algebra.expressions.AbstractFunctionCallExpression;
  import org.apache.hyracks.algebricks.core.algebra.expressions.ConstantExpression;
  import org.apache.hyracks.algebricks.core.algebra.expressions.IVariableTypeEnvironment;
  import org.apache.hyracks.algebricks.core.algebra.expressions.ScalarFunctionCallExpression;
  import org.apache.hyracks.algebricks.core.algebra.expressions.VariableReferenceExpression;
  import org.apache.hyracks.algebricks.core.algebra.operators.logical.AssignOperator;
  import org.apache.hyracks.algebricks.core.rewriter.base.IAlgebraicRewriteRule;
  import org.apache.hyracks.api.exceptions.SourceLocation;
  
  public class ByNameToByIndexFieldAccessRule implements IAlgebraicRewriteRule {
  
      private final boolean includeNameToIndexRewrite;
  
      public ByNameToByIndexFieldAccessRule(boolean includeNameToIndexRewrite) {
          this.includeNameToIndexRewrite = includeNameToIndexRewrite;
      }
  
      @Override
      public boolean rewritePre(Mutable<ILogicalOperator> opRef, IOptimizationContext context)
              throws AlgebricksException {
          return false;
      }
  
      @Override
      public boolean rewritePost(Mutable<ILogicalOperator> opRef, IOptimizationContext context)
              throws AlgebricksException {
          ILogicalOperator op = opRef.getValue();
          if (op.acceptExpressionTransform(exprRef -> rewriteExpressionReference(op, exprRef, context))) {
              op.removeAnnotation(OperatorAnnotation.PUSHED_FIELD_ACCESS);
              context.computeAndSetTypeEnvironmentForOperator(op);
              return true;
          }
          return false;
      }
  
      // Recursively rewrites expression reference.
      private boolean rewriteExpressionReference(ILogicalOperator op, Mutable<ILogicalExpression> exprRef,
              IOptimizationContext context) throws AlgebricksException {
          ILogicalExpression expr = exprRef.getValue();
          if (expr.getExpressionTag() != LogicalExpressionTag.FUNCTION_CALL) {
              return false;
          }
          boolean changed = false;
          AbstractFunctionCallExpression fce = (AbstractFunctionCallExpression) expr;
          for (Mutable<ILogicalExpression> funcArgRef : fce.getArguments()) {
              if (rewriteExpressionReference(op, funcArgRef, context)) {
                  changed = true;
              }
          }
          if (fce.getFunctionIdentifier() != BuiltinFunctions.FIELD_ACCESS_BY_NAME) {
              return changed;
          }
          changed |= extractFirstArg(fce, op, context);
          if (includeNameToIndexRewrite) {
              IVariableTypeEnvironment env = context.getOutputTypeEnvironment(op.getInputs().get(0).getValue());
              IAType t = (IAType) env.getType(fce.getArguments().get(0).getValue());
              changed |= rewriteFieldAccess(exprRef, fce, TypeComputeUtils.getActualType(t));
          }
          return changed;
      }
  
      // Extracts the first argument of a field-access expression into an separate assign operator.
      private boolean extractFirstArg(AbstractFunctionCallExpression fce, ILogicalOperator op,
              IOptimizationContext context) throws AlgebricksException {
          ILogicalExpression firstArg = fce.getArguments().get(0).getValue();
          if (firstArg.getExpressionTag() != LogicalExpressionTag.FUNCTION_CALL) {
              return false;
          }
          SourceLocation sourceLoc = firstArg.getSourceLocation();
          LogicalVariable var1 = context.newVar();
          AssignOperator assignOp = new AssignOperator(new ArrayList<>(Collections.singletonList(var1)),
                  new ArrayList<>(Collections.singletonList(new MutableObject<>(firstArg))));
          assignOp.setSourceLocation(sourceLoc);
          VariableReferenceExpression var1Ref = new VariableReferenceExpression(var1);
          var1Ref.setSourceLocation(sourceLoc);
          fce.getArguments().get(0).setValue(var1Ref);
          assignOp.getInputs().add(new MutableObject<>(op.getInputs().get(0).getValue()));
          op.getInputs().get(0).setValue(assignOp);
          context.computeAndSetTypeEnvironmentForOperator(assignOp);
          return true;
      }
  
      // Rewrites field-access-by-name into field-access-by-index if possible.
      private boolean rewriteFieldAccess(Mutable<ILogicalExpression> exprRef, AbstractFunctionCallExpression fce,
              IAType t) {
          if (t.getTypeTag() != ATypeTag.OBJECT) {
              return false;
          }
          ILogicalExpression fai = createFieldAccessByIndex((ARecordType) t, fce);
          boolean changed = fai != null;
          if (changed) {
              exprRef.setValue(fai);
          }
          return changed;
      }
  
      private static ILogicalExpression createFieldAccessByIndex(ARecordType recType,
              AbstractFunctionCallExpression fce) {
          String s = ConstantExpressionUtil.getStringArgument(fce, 1);
          if (s == null) {
              return null;
          }
          int k = recType.getFieldIndex(s);
          if (k < 0) {
              return null;
          }
          ScalarFunctionCallExpression faExpr = new ScalarFunctionCallExpression(
                  BuiltinFunctions.getBuiltinFunctionInfo(BuiltinFunctions.FIELD_ACCESS_BY_INDEX),
                  fce.getArguments().get(0),
                  new MutableObject<>(new ConstantExpression(new AsterixConstantValue(new AInt32(k)))));
          faExpr.setSourceLocation(fce.getSourceLocation());
          return faExpr;
      }
  }
  