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.lang.sqlpp.visitor;
  
  import java.util.Collections;
  
  import org.apache.asterix.common.metadata.DataverseName;
  import org.apache.asterix.common.metadata.Namespace;
  import org.apache.asterix.lang.common.base.Expression;
  import org.apache.asterix.lang.common.clause.WhereClause;
  import org.apache.asterix.lang.common.expression.CallExpr;
  import org.apache.asterix.lang.common.expression.VariableExpr;
  import org.apache.asterix.lang.common.statement.DeleteStatement;
  import org.apache.asterix.lang.common.statement.Query;
  import org.apache.asterix.lang.common.util.FunctionUtil;
  import org.apache.asterix.lang.sqlpp.clause.FromClause;
  import org.apache.asterix.lang.sqlpp.clause.FromTerm;
  import org.apache.asterix.lang.sqlpp.clause.SelectBlock;
  import org.apache.asterix.lang.sqlpp.clause.SelectClause;
  import org.apache.asterix.lang.sqlpp.clause.SelectElement;
  import org.apache.asterix.lang.sqlpp.clause.SelectSetOperation;
  import org.apache.asterix.lang.sqlpp.expression.SelectExpression;
  import org.apache.asterix.lang.sqlpp.struct.SetOperationInput;
  import org.apache.asterix.lang.sqlpp.visitor.base.AbstractSqlppAstVisitor;
  import org.apache.asterix.metadata.declared.MetadataProvider;
  
  /**
   * This class rewrites delete statement to contain a query that specifying
   * what to delete.
   */
  public class SqlppDeleteRewriteVisitor extends AbstractSqlppAstVisitor<Void, MetadataProvider> {
  
      public static final SqlppDeleteRewriteVisitor INSTANCE = new SqlppDeleteRewriteVisitor();
  
      private SqlppDeleteRewriteVisitor() {
      }
  
      @Override
      public Void visit(DeleteStatement deleteStmt, MetadataProvider metadataProvider) {
          DataverseName dataverseName = deleteStmt.getDataverseName();
          String databaseName = deleteStmt.getDatabaseName();
          if (dataverseName == null) {
              Namespace defaultNamespace = metadataProvider.getDefaultNamespace();
              dataverseName = defaultNamespace.getDataverseName();
              databaseName = defaultNamespace.getDatabaseName();
          }
          String datasetName = deleteStmt.getDatasetName();
          CallExpr callExpression = FunctionUtil.makeDatasetCallExpr(databaseName, dataverseName, datasetName);
          callExpression.setSourceLocation(deleteStmt.getSourceLocation());
  
          // From clause.
          VariableExpr var = deleteStmt.getVariableExpr();
          FromTerm fromTerm = new FromTerm(callExpression, var, null, null);
          fromTerm.setSourceLocation(var.getSourceLocation());
          FromClause fromClause = new FromClause(Collections.singletonList(fromTerm));
          fromClause.setSourceLocation(var.getSourceLocation());
  
          // Where clause.
          WhereClause whereClause = null;
          Expression condition = deleteStmt.getCondition();
          if (condition != null) {
              whereClause = new WhereClause(condition);
              whereClause.setSourceLocation(condition.getSourceLocation());
          }
  
          // Select clause.
          VariableExpr returnExpr = new VariableExpr(var.getVar());
          returnExpr.setIsNewVar(false);
          returnExpr.setSourceLocation(var.getSourceLocation());
          SelectElement selectElement = new SelectElement(returnExpr);
          selectElement.setSourceLocation(deleteStmt.getSourceLocation());
          SelectClause selectClause = new SelectClause(selectElement, null, false);
          selectClause.setSourceLocation(deleteStmt.getSourceLocation());
  
          // Construct the select expression.
          SelectBlock selectBlock = new SelectBlock(selectClause, fromClause,
                  whereClause != null ? Collections.singletonList(whereClause) : null, null, null);
          selectBlock.setSourceLocation(var.getSourceLocation());
          SelectSetOperation selectSetOperation = new SelectSetOperation(new SetOperationInput(selectBlock, null), null);
          selectSetOperation.setSourceLocation(var.getSourceLocation());
          SelectExpression selectExpression = new SelectExpression(null, selectSetOperation, null, null, false);
          selectExpression.setSourceLocation(var.getSourceLocation());
          Query query = new Query(false, false, false, selectExpression, 0);
          query.setBody(selectExpression);
          query.setSourceLocation(deleteStmt.getSourceLocation());
  
          // return the delete statement.
          deleteStmt.setQuery(query);
          return null;
      }
  }
  