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   * 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 java.util.List;
  
  import org.apache.asterix.common.exceptions.CompilationException;
  import org.apache.asterix.common.exceptions.ErrorCode;
  import org.apache.asterix.metadata.functions.ExternalFunctionCompilerUtil;
  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.VariableReferenceExpression;
  import org.apache.hyracks.algebricks.core.algebra.functions.IFunctionInfo;
  import org.apache.hyracks.algebricks.core.algebra.operators.logical.AbstractLogicalOperator;
  import org.apache.hyracks.algebricks.core.algebra.operators.logical.AssignOperator;
  import org.apache.hyracks.algebricks.core.algebra.util.OperatorManipulationUtil;
  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;
  import org.apache.hyracks.api.exceptions.SourceLocation;
  
  public class ExtractBatchableExternalFunctionCallsRule implements IAlgebraicRewriteRule {
  
      private final ExtractFunctionCallsVisitor extractVisitor = new ExtractFunctionCallsVisitor();
  
      private Boolean isRuleEnabled;
  
      @Override
      public boolean rewritePre(Mutable<ILogicalOperator> opRef, IOptimizationContext context) {
          return false;
      }
  
      @Override
      public boolean rewritePost(Mutable<ILogicalOperator> opRef, IOptimizationContext context)
              throws AlgebricksException {
          if (isRuleEnabled == null) {
              isRuleEnabled = SetAsterixPhysicalOperatorsRule.isBatchAssignEnabled(context);
          }
          if (!isRuleEnabled) {
              return false;
          }
  
          AbstractLogicalOperator op = (AbstractLogicalOperator) opRef.getValue();
          List<Mutable<ILogicalExpression>> assignTopExprRefs = Collections.emptyList();
          switch (op.getOperatorTag()) {
              case ASSIGN:
                  assignTopExprRefs = ((AssignOperator) op).getExpressions();
                  break;
              case SELECT:
                  break;
              default:
                  return false;
          }
  
          if (context.checkIfInDontApplySet(this, op)) {
              return false;
          }
          context.addToDontApplySet(this, op);
  
          extractVisitor.reset(context, assignTopExprRefs);
          if (!op.acceptExpressionTransform(extractVisitor)) {
              return false;
          }
          SourceLocation sourceLoc = op.getSourceLocation();
  
          ILogicalOperator inputOp = op.getInputs().get(0).getValue();
          for (int i = 0, ln = extractVisitor.assignVars.size(); i < ln; i++) {
              List<LogicalVariable> assignVarList = extractVisitor.assignVars.get(i);
              List<Mutable<ILogicalExpression>> assignExprList = extractVisitor.assignExprs.get(i);
              AssignOperator assignOp = new AssignOperator(assignVarList, assignExprList);
              assignOp.setSourceLocation(sourceLoc);
              assignOp.getInputs().add(new MutableObject<>(inputOp));
              context.computeAndSetTypeEnvironmentForOperator(assignOp);
              assignOp.recomputeSchema();
              OperatorPropertiesUtil.markMovable(assignOp, false);
  
              context.addToDontApplySet(this, assignOp);
              for (LogicalVariable assignVar : assignVarList) {
                  context.addNotToBeInlinedVar(assignVar);
              }
  
              inputOp = assignOp;
          }
  
          op.getInputs().clear();
          op.getInputs().add(new MutableObject<>(inputOp));
          context.computeAndSetTypeEnvironmentForOperator(op);
          op.recomputeSchema();
          return true;
      }
  
      private static final class ExtractFunctionCallsVisitor implements ILogicalExpressionReferenceTransform {
  
          private final List<List<LogicalVariable>> assignVars = new ArrayList<>();
  
          private final List<List<Mutable<ILogicalExpression>>> assignExprs = new ArrayList<>();
  
          private final List<LogicalVariable> usedVarList = new ArrayList<>();
  
          private IOptimizationContext context;
  
          private List<Mutable<ILogicalExpression>> dontExtractFromExprRefs;
  
          public void reset(IOptimizationContext context, List<Mutable<ILogicalExpression>> dontExtractFromExprRefs) {
              this.context = context;
              this.dontExtractFromExprRefs = dontExtractFromExprRefs;
              assignVars.clear();
              assignExprs.clear();
          }
  
          @Override
          public boolean transform(Mutable<ILogicalExpression> exprRef) throws AlgebricksException {
              ILogicalExpression expr = exprRef.getValue();
              switch (expr.getExpressionTag()) {
                  case FUNCTION_CALL:
                      AbstractFunctionCallExpression callExpr = (AbstractFunctionCallExpression) expr;
                      boolean applied = false;
                      for (Mutable<ILogicalExpression> argRef : callExpr.getArguments()) {
                          applied |= transform(argRef);
                      }
                      AbstractFunctionCallExpression.FunctionKind fnKind = callExpr.getKind();
                      IFunctionInfo fnInfo = callExpr.getFunctionInfo();
                      if (ExternalFunctionCompilerUtil.supportsBatchInvocation(fnKind, fnInfo)
                              && callExpr.isFunctional()) {
                          // need to extract non-variable arguments into separate ASSIGNS
                          // because batched assign can only operate on columns
                          for (Mutable<ILogicalExpression> argRef : callExpr.getArguments()) {
                              ILogicalExpression argExpr = argRef.getValue();
                              if (argExpr.getExpressionTag() != LogicalExpressionTag.VARIABLE) {
                                  LogicalVariable newArgVar = context.newVar();
                                  VariableReferenceExpression newArgVarRef = new VariableReferenceExpression(newArgVar);
                                  newArgVarRef.setSourceLocation(expr.getSourceLocation());
                                  saveAssignVar(newArgVar, argExpr);
                                  argRef.setValue(newArgVarRef);
                                  applied = true;
                              }
                          }
                          // need extract function call itself into a separate ASSIGN
                          // (unless it's already a top level expression of the ASSIGN operator we're visiting)
                          boolean dontExtractExprRef = indexOf(dontExtractFromExprRefs, exprRef) >= 0;
                          if (!dontExtractExprRef) {
                              LogicalVariable newVar = context.newVar();
                              VariableReferenceExpression newVarRef = new VariableReferenceExpression(newVar);
                              newVarRef.setSourceLocation(expr.getSourceLocation());
                              saveAssignVar(newVar, expr);
                              exprRef.setValue(newVarRef);
                              applied = true;
                          }
                      }
                      return applied;
                  case VARIABLE:
                  case CONSTANT:
                      return false;
                  default:
                      throw new CompilationException(ErrorCode.COMPILATION_ILLEGAL_STATE, expr.getSourceLocation(),
                              expr.getExpressionTag().toString());
              }
          }
  
          private void saveAssignVar(LogicalVariable var, ILogicalExpression expr) {
              List<LogicalVariable> assignVarList = null;
              List<Mutable<ILogicalExpression>> assignExprList = null;
  
              if (!assignVars.isEmpty()) {
                  usedVarList.clear();
                  expr.getUsedVariables(usedVarList);
                  int candidateVarListIdx = assignVars.size() - 1;
                  List<LogicalVariable> candidateVarList = assignVars.get(candidateVarListIdx);
                  if (OperatorPropertiesUtil.disjoint(candidateVarList, usedVarList)) {
                      assignVarList = candidateVarList;
                      assignExprList = assignExprs.get(candidateVarListIdx);
                  }
              }
  
              if (assignVarList == null) {
                  // first time, or couldn't find a disjoint var list
                  assignVarList = new ArrayList<>();
                  assignExprList = new ArrayList<>();
                  assignVars.add(assignVarList);
                  assignExprs.add(assignExprList);
              }
  
              assignVarList.add(var);
              assignExprList.add(new MutableObject<>(expr));
          }
  
          public static int indexOf(List<Mutable<ILogicalExpression>> exprList, Mutable<ILogicalExpression> exprRef) {
              return OperatorManipulationUtil.indexOf(exprList,
                      (listItemExprRef, paramExprRef) -> listItemExprRef == paramExprRef, exprRef);
          }
      }
  }
  