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   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
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   * 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
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   *
   *   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
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  package org.apache.asterix.optimizer.rules;
  
  import java.util.ArrayList;
  import java.util.HashSet;
  import java.util.Iterator;
  import java.util.LinkedList;
  import java.util.List;
  
  import org.apache.asterix.algebra.base.OperatorAnnotation;
  import org.apache.asterix.common.exceptions.CompilationException;
  import org.apache.asterix.common.exceptions.ErrorCode;
  import org.apache.asterix.lang.common.util.FunctionUtil;
  import org.apache.asterix.om.base.AInt32;
  import org.apache.asterix.om.base.AString;
  import org.apache.asterix.om.constants.AsterixConstantValue;
  import org.apache.asterix.om.functions.BuiltinFunctions;
  import org.apache.asterix.om.types.ARecordType;
  import org.apache.asterix.om.utils.ConstantExpressionUtil;
  import org.apache.asterix.optimizer.base.AnalysisUtil;
  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.ILogicalPlan;
  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.base.LogicalVariable;
  import org.apache.hyracks.algebricks.core.algebra.expressions.AbstractFunctionCallExpression;
  import org.apache.hyracks.algebricks.core.algebra.expressions.AbstractLogicalExpression;
  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.VariableReferenceExpression;
  import org.apache.hyracks.algebricks.core.algebra.functions.AlgebricksBuiltinFunctions;
  import org.apache.hyracks.algebricks.core.algebra.functions.FunctionIdentifier;
  import org.apache.hyracks.algebricks.core.algebra.operators.logical.AbstractLogicalOperator;
  import org.apache.hyracks.algebricks.core.algebra.operators.logical.AbstractOperatorWithNestedPlans;
  import org.apache.hyracks.algebricks.core.algebra.operators.logical.AssignOperator;
  import org.apache.hyracks.algebricks.core.algebra.operators.logical.NestedTupleSourceOperator;
  import org.apache.hyracks.algebricks.core.algebra.operators.logical.SelectOperator;
  import org.apache.hyracks.algebricks.core.algebra.operators.logical.visitors.VariableUtilities;
  import org.apache.hyracks.algebricks.core.algebra.properties.FunctionalDependency;
  import org.apache.hyracks.algebricks.core.algebra.util.OperatorPropertiesUtil;
  import org.apache.hyracks.algebricks.core.algebra.visitors.ILogicalExpressionReferenceTransform;
  import org.apache.hyracks.algebricks.core.rewriter.base.IAlgebraicRewriteRule;
  
  public class LoadRecordFieldsRule implements IAlgebraicRewriteRule {
  
      private final ExtractFieldLoadExpressionVisitor exprVisitor = new ExtractFieldLoadExpressionVisitor();
  
      @Override
      public boolean rewritePre(Mutable<ILogicalOperator> opRef, IOptimizationContext context) {
          return false;
      }
  
      @Override
      public boolean rewritePost(Mutable<ILogicalOperator> opRef, IOptimizationContext context)
              throws AlgebricksException {
          AbstractLogicalOperator op1 = (AbstractLogicalOperator) opRef.getValue();
          if (context.checkIfInDontApplySet(this, op1)) {
              return false;
          }
  
          if (op1.getOperatorTag() == LogicalOperatorTag.ASSIGN) {
              AssignOperator a1 = (AssignOperator) op1;
              ILogicalExpression expr = getFirstExpr(a1);
              if (AnalysisUtil.isAccessToFieldRecord(expr)) {
                  boolean res = findAndEliminateRedundantFieldAccess(a1, context);
                  context.addToDontApplySet(this, op1);
                  return res;
              }
          }
          exprVisitor.setTopOp(op1);
          exprVisitor.setContext(context);
          boolean res = op1.acceptExpressionTransform(exprVisitor);
          if (!res) {
              context.addToDontApplySet(this, op1);
          }
          if (res && op1.getOperatorTag() == LogicalOperatorTag.SELECT) {
              // checking if we can annotate a Selection as using just one field
              // access
              SelectOperator sigma = (SelectOperator) op1;
              List<LogicalVariable> vars = new ArrayList<>();
              VariableUtilities.getUsedVariables(sigma, vars);
              if (vars.size() == 1) {
                  // we can annotate Selection
                  AssignOperator assign1 = (AssignOperator) op1.getInputs().get(0).getValue();
                  ILogicalExpression expr1 = getFirstExpr(assign1);
                  if (FunctionUtil.isFieldAccessFunction(expr1)) {
                      AbstractFunctionCallExpression f = (AbstractFunctionCallExpression) expr1;
                      // f should be a call to a field/data access kind of
                      // function
                      sigma.getAnnotations().put(OperatorAnnotation.FIELD_ACCESS, f.getArguments().get(0));
                  }
              }
          }
  
          // TODO: avoid having to recompute type env. here
          if (res) {
              OperatorPropertiesUtil.typeOpRec(opRef, context);
          }
          return res;
      }
  
      private static boolean pushFieldLoads(Mutable<ILogicalExpression> exprRef, AbstractLogicalOperator topOp,
              IOptimizationContext context) throws AlgebricksException {
          ILogicalExpression expr = exprRef.getValue();
          if (expr == null) {
              return false;
          }
          switch (expr.getExpressionTag()) {
              case FUNCTION_CALL: {
                  AbstractFunctionCallExpression f = (AbstractFunctionCallExpression) expr;
                  FunctionIdentifier fi = f.getFunctionIdentifier();
                  if (AlgebricksBuiltinFunctions.isComparisonFunction(fi)) {
                      boolean b1 = pushFieldLoads(f.getArguments().get(0), topOp, context);
                      boolean b2 = pushFieldLoads(f.getArguments().get(1), topOp, context);
                      return b1 || b2;
                  }
                  if (fi.equals(BuiltinFunctions.FIELD_ACCESS_BY_NAME)) {
                      if (AnalysisUtil.numberOfVarsInExpr(f) == 0) {
                          return false;
                      }
                      // create an assign
                      LogicalVariable v = context.newVar();
                      AssignOperator a2 = new AssignOperator(v, new MutableObject<>(f));
                      a2.setSourceLocation(expr.getSourceLocation());
                      pushFieldAssign(a2, topOp, context);
                      context.computeAndSetTypeEnvironmentForOperator(a2);
                      ILogicalExpression arg = f.getArguments().get(0).getValue();
                      if (arg.getExpressionTag() == LogicalExpressionTag.VARIABLE) {
                          VariableReferenceExpression ref = (VariableReferenceExpression) arg;
                          LogicalVariable var = ref.getVariableReference();
                          List<LogicalVariable> keys = context.findPrimaryKey(var);
                          if (keys != null) {
                              List<LogicalVariable> tail = new ArrayList<>();
                              tail.add(v);
                              FunctionalDependency pk = new FunctionalDependency(keys, tail);
                              context.addPrimaryKey(pk);
                          }
                      }
                      VariableReferenceExpression varRef = new VariableReferenceExpression(v);
                      varRef.setSourceLocation(expr.getSourceLocation());
                      exprRef.setValue(varRef);
                      return true;
                  } else {
                      boolean pushed = false;
                      for (Mutable<ILogicalExpression> argRef : f.getArguments()) {
                          if (pushFieldLoads(argRef, topOp, context)) {
                              pushed = true;
                          }
                      }
                      return pushed;
                  }
              }
              case CONSTANT:
              case VARIABLE: {
                  return false;
              }
              default: {
                  assert false;
                  throw new IllegalArgumentException();
              }
          }
      }
  
      private static void pushFieldAssign(AssignOperator a2, AbstractLogicalOperator topOp, IOptimizationContext context)
              throws AlgebricksException {
          if (topOp.getInputs().size() == 1 && !topOp.hasNestedPlans()) {
              Mutable<ILogicalOperator> topChild = topOp.getInputs().get(0);
              // plugAccessAboveOp(a2, topChild, context);
              List<Mutable<ILogicalOperator>> a2InptList = a2.getInputs();
              a2InptList.clear();
              a2InptList.add(topChild);
              // and link it as child in the op. tree
              topOp.getInputs().set(0, new MutableObject<>(a2));
              findAndEliminateRedundantFieldAccess(a2, context);
          } else { // e.g., a join
              LinkedList<LogicalVariable> usedInAccess = new LinkedList<LogicalVariable>();
              VariableUtilities.getUsedVariables(a2, usedInAccess);
  
              LinkedList<LogicalVariable> produced2 = new LinkedList<LogicalVariable>();
              VariableUtilities.getProducedVariables(topOp, produced2);
  
              if (OperatorPropertiesUtil.disjoint(produced2, usedInAccess)) {
                  for (Mutable<ILogicalOperator> inp : topOp.getInputs()) {
                      HashSet<LogicalVariable> v2 = new HashSet<LogicalVariable>();
                      VariableUtilities.getLiveVariables(inp.getValue(), v2);
                      if (!OperatorPropertiesUtil.disjoint(usedInAccess, v2)) {
                          pushAccessAboveOpRef(a2, inp, context);
                          return;
                      }
                  }
                  if (topOp.hasNestedPlans()) {
                      AbstractOperatorWithNestedPlans nestedOp = (AbstractOperatorWithNestedPlans) topOp;
                      for (ILogicalPlan plan : nestedOp.getNestedPlans()) {
                          for (Mutable<ILogicalOperator> root : plan.getRoots()) {
                              HashSet<LogicalVariable> v2 = new HashSet<LogicalVariable>();
                              VariableUtilities.getLiveVariables(root.getValue(), v2);
                              if (!OperatorPropertiesUtil.disjoint(usedInAccess, v2)) {
                                  pushAccessAboveOpRef(a2, root, context);
                                  return;
                              }
                          }
                      }
                  }
                  throw new CompilationException(ErrorCode.COMPILATION_ERROR, a2.getSourceLocation(),
                          "Field access " + getFirstExpr(a2) + " does not correspond to any input");
              }
          }
      }
  
      /**
       * Pushes one field-access assignment above toPushThroughChildRef
       *
       * @param toPush
       * @param toPushThroughChildRef
       */
      private static void pushAccessAboveOpRef(AssignOperator toPush, Mutable<ILogicalOperator> toPushThroughChildRef,
              IOptimizationContext context) throws AlgebricksException {
          List<Mutable<ILogicalOperator>> tpInpList = toPush.getInputs();
          tpInpList.clear();
          tpInpList.add(new MutableObject<>(toPushThroughChildRef.getValue()));
          toPushThroughChildRef.setValue(toPush);
          findAndEliminateRedundantFieldAccess(toPush, context);
      }
  
      /**
       * Rewrite
       * assign $x := field-access($y, "field")
       * assign $y := record-constructor { "field": Expr, ... }
       * into
       * assign $x := Expr
       * assign $y := record-constructor { "field": Expr, ... }
       */
      private static boolean findAndEliminateRedundantFieldAccess(AssignOperator assign, IOptimizationContext context)
              throws AlgebricksException {
          ILogicalExpression expr = getFirstExpr(assign);
          AbstractFunctionCallExpression f = (AbstractFunctionCallExpression) expr;
          ILogicalExpression arg0 = f.getArguments().get(0).getValue();
          if (arg0.getExpressionTag() != LogicalExpressionTag.VARIABLE) {
              return false;
          }
          VariableReferenceExpression vre = (VariableReferenceExpression) arg0;
          LogicalVariable recordVar = vre.getVariableReference();
          ILogicalExpression arg1 = f.getArguments().get(1).getValue();
          if (arg1.getExpressionTag() != LogicalExpressionTag.CONSTANT) {
              return false;
          }
          IVariableTypeEnvironment typeEnvironment = context.getOutputTypeEnvironment(assign);
          ConstantExpression ce = (ConstantExpression) arg1;
          ILogicalExpression fldExpr;
          if (f.getFunctionIdentifier().equals(BuiltinFunctions.FIELD_ACCESS_BY_NAME)) {
              String fldName = ((AString) ((AsterixConstantValue) ce.getValue()).getObject()).getStringValue();
              fldExpr = findFieldExpression(assign, recordVar, fldName, typeEnvironment,
                      (name, expression, env) -> findFieldByNameFromRecordConstructor(name, expression));
          } else if (f.getFunctionIdentifier().equals(BuiltinFunctions.FIELD_ACCESS_BY_INDEX)) {
              Integer fldIdx = ((AInt32) ((AsterixConstantValue) ce.getValue()).getObject()).getIntegerValue();
              fldExpr = findFieldExpression(assign, recordVar, fldIdx, typeEnvironment,
                      LoadRecordFieldsRule::findFieldByIndexFromRecordConstructor);
          } else if (f.getFunctionIdentifier().equals(BuiltinFunctions.FIELD_ACCESS_NESTED)) {
              return false;
          } else {
              throw new IllegalStateException();
          }
  
          if (fldExpr == null) {
              return false;
          }
          // check the liveness of the new expression
          List<LogicalVariable> usedVariables = new ArrayList<>();
          fldExpr.getUsedVariables(usedVariables);
          List<LogicalVariable> liveInputVars = new ArrayList<>();
          VariableUtilities.getLiveVariables(assign, liveInputVars);
          usedVariables.removeAll(liveInputVars);
          if (usedVariables.isEmpty()) {
              assign.getExpressions().get(0).setValue(fldExpr.cloneExpression());
              return true;
          } else {
              return false;
          }
      }
  
      @FunctionalInterface
      private interface FieldResolver {
          ILogicalExpression resolve(Object accessKey, AbstractFunctionCallExpression funcExpr,
                  IVariableTypeEnvironment typeEnvironment) throws AlgebricksException;
      }
  
      // Finds a field expression.
      private static ILogicalExpression findFieldExpression(AbstractLogicalOperator op, LogicalVariable recordVar,
              Object accessKey, IVariableTypeEnvironment typeEnvironment, FieldResolver resolver)
              throws AlgebricksException {
          List<Mutable<ILogicalOperator>> inputs = op.getInputs();
          int inputIdxLimit;
          if (op.getOperatorTag() == LogicalOperatorTag.LEFTOUTERJOIN) {
              // do not search in the right branch of a left outer join
              inputIdxLimit = 1;
          } else {
              inputIdxLimit = inputs.size();
          }
  
          for (int inputIdx = 0; inputIdx < inputIdxLimit; inputIdx++) {
              Mutable<ILogicalOperator> child = inputs.get(inputIdx);
              AbstractLogicalOperator opChild = (AbstractLogicalOperator) child.getValue();
              if (opChild.getOperatorTag() == LogicalOperatorTag.ASSIGN) {
                  AssignOperator op2 = (AssignOperator) opChild;
                  int i = op2.getVariables().indexOf(recordVar);
                  if (i >= 0) {
                      AbstractLogicalExpression constr =
                              (AbstractLogicalExpression) op2.getExpressions().get(i).getValue();
                      return resolveFieldExpression(constr, accessKey, typeEnvironment, resolver);
                  }
              } else if (opChild.getOperatorTag() == LogicalOperatorTag.NESTEDTUPLESOURCE) {
                  NestedTupleSourceOperator nts = (NestedTupleSourceOperator) opChild;
                  AbstractLogicalOperator opWithNestedPlan =
                          (AbstractLogicalOperator) nts.getDataSourceReference().getValue();
                  ILogicalExpression expr1 =
                          findFieldExpression(opWithNestedPlan, recordVar, accessKey, typeEnvironment, resolver);
                  if (expr1 != null) {
                      return expr1;
                  }
              }
              ILogicalExpression expr2 = findFieldExpression(opChild, recordVar, accessKey, typeEnvironment, resolver);
              if (expr2 != null) {
                  return expr2;
              }
          }
          return null;
      }
  
      // Resolves field expression from an access key and a field resolver.
      private static ILogicalExpression resolveFieldExpression(AbstractLogicalExpression constr, Object accessKey,
              IVariableTypeEnvironment typeEnvironment, FieldResolver resolver) throws AlgebricksException {
          if (constr.getExpressionTag() != LogicalExpressionTag.FUNCTION_CALL) {
              return null;
          }
          AbstractFunctionCallExpression fce = (AbstractFunctionCallExpression) constr;
          if (!fce.getFunctionIdentifier().equals(BuiltinFunctions.OPEN_RECORD_CONSTRUCTOR)
                  && !fce.getFunctionIdentifier().equals(BuiltinFunctions.CLOSED_RECORD_CONSTRUCTOR)) {
              return null;
          }
          return resolver.resolve(accessKey, fce, typeEnvironment);
      }
  
      // Resolves field expression by name-based access.
      private static ILogicalExpression findFieldByNameFromRecordConstructor(Object fldName,
              AbstractFunctionCallExpression fce) {
          Iterator<Mutable<ILogicalExpression>> fldIter = fce.getArguments().iterator();
          while (fldIter.hasNext()) {
              ILogicalExpression fldExpr = fldIter.next().getValue();
              if (fldName.equals(ConstantExpressionUtil.getStringConstant(fldExpr))) {
                  return fldIter.next().getValue();
              }
              fldIter.next();
          }
          return null;
      }
  
      // Resolves field expression by index-based access.
      private static ILogicalExpression findFieldByIndexFromRecordConstructor(Object index,
              AbstractFunctionCallExpression fce, IVariableTypeEnvironment typeEnvironment) throws AlgebricksException {
          Integer fieldIndex = (Integer) index;
          ARecordType recordType = (ARecordType) typeEnvironment.getType(fce);
          String[] closedFieldNames = recordType.getFieldNames();
          return closedFieldNames.length > fieldIndex
                  ? findFieldByNameFromRecordConstructor(closedFieldNames[fieldIndex], fce) : null;
      }
  
      private final class ExtractFieldLoadExpressionVisitor implements ILogicalExpressionReferenceTransform {
  
          private AbstractLogicalOperator topOp;
          private IOptimizationContext context;
  
          public void setTopOp(AbstractLogicalOperator topOp) {
              this.topOp = topOp;
          }
  
          public void setContext(IOptimizationContext context) {
              this.context = context;
          }
  
          @Override
          public boolean transform(Mutable<ILogicalExpression> exprRef) throws AlgebricksException {
              return pushFieldLoads(exprRef, topOp, context);
          }
  
      }
  
      private static ILogicalExpression getFirstExpr(AssignOperator assign) {
          return assign.getExpressions().get(0).getValue();
      }
  }
  