Sequence.java :  » Database-DBMS » mckoi » com » mckoi » database » interpret » Java Open Source

/**
 * com.mckoi.database.interpret.Sequence  07 Apr 2003
 *
 * Mckoi SQL Database ( http://www.mckoi.com/database )
 * Copyright (C) 2000, 2001, 2002  Diehl and Associates, Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * Version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License Version 2 for more details.
 *
 * You should have received a copy of the GNU General Public License
 * Version 2 along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * Change Log:
 * 
 * 
 */

package com.mckoi.database.interpret;

import com.mckoi.database.*;
import com.mckoi.debug.*;

/**
 * A statement tree for creating and dropping sequence generators.
 *
 * @author Tobias Downer
 */

public class Sequence extends Statement {

  String type;
  
  TableName seq_name;
  
  Expression increment;
  Expression min_value;
  Expression max_value;
  Expression start_value;
  Expression cache_value;
  boolean cycle;
  
  // ----------- Implemented from Statement ----------
  
  public void prepare() throws DatabaseException {
    type = (String) cmd.getObject("type");
    String sname = (String) cmd.getObject("seq_name");
    String schema_name = database.getCurrentSchema();
    seq_name = TableName.resolve(schema_name, sname);
    seq_name = database.tryResolveCase(seq_name);

    if (type.equals("create")) {
      // Resolve the function name into a TableName object.    
      increment = (Expression) cmd.getObject("increment");
      min_value = (Expression) cmd.getObject("min_value");
      max_value = (Expression) cmd.getObject("max_value");
      start_value = (Expression) cmd.getObject("start");
      cache_value = (Expression) cmd.getObject("cache");
      cycle = cmd.getObject("cycle") != null;
    }

  }

  public Table evaluate() throws DatabaseException {
    
    DatabaseQueryContext context = new DatabaseQueryContext(database);

    // Does the schema exist?
    boolean ignore_case = database.isInCaseInsensitiveMode();
    SchemaDef schema =
              database.resolveSchemaCase(seq_name.getSchema(), ignore_case);
    if (schema == null) {
      throw new DatabaseException("Schema '" + seq_name.getSchema() +
                                  "' doesn't exist.");
    }
    else {
      seq_name = new TableName(schema.getName(), seq_name.getName());
    }

    if (type.equals("create")) {

      // Does the user have privs to create this sequence generator?
      if (!database.getDatabase().canUserCreateSequenceObject(context,
                                                              user, seq_name)) {
        throw new UserAccessException(
                        "User not permitted to create sequence: " + seq_name);
      }

      // Does a table already exist with this name?
      if (database.tableExists(seq_name)) {
        throw new DatabaseException("Database object with name '" + seq_name +
                                    "' already exists.");
      }

      // Resolve the expressions,
      long v_start_value = 0;
      if (start_value != null) {
        v_start_value =
           start_value.evaluate(null, null, context).toBigNumber().longValue();
      }
      long v_increment_by = 1;
      if (increment != null) {
        v_increment_by =
             increment.evaluate(null, null, context).toBigNumber().longValue();
      }
      long v_min_value = 0;
      if (min_value != null) {
        v_min_value =
             min_value.evaluate(null, null, context).toBigNumber().longValue();
      }
      long v_max_value = Long.MAX_VALUE;
      if (max_value != null) {
        v_max_value =
             max_value.evaluate(null, null, context).toBigNumber().longValue();
      }
      long v_cache = 16;
      if (cache_value != null) {
        v_cache =
           cache_value.evaluate(null, null, context).toBigNumber().longValue();
        if (v_cache <= 0) {
          throw new DatabaseException("Cache size can not be <= 0");
        }
      }

      if (v_min_value >= v_max_value) {
        throw new DatabaseException("Min value can not be >= the max value.");
      }
      if (v_start_value < v_min_value ||
          v_start_value >= v_max_value) {
        throw new DatabaseException(
                       "Start value is outside the min/max sequence bounds.");
      }

      database.createSequenceGenerator(seq_name,
             v_start_value, v_increment_by, v_min_value, v_max_value,
             v_cache, cycle);

      // The initial grants for a sequence is to give the user who created it
      // full access.
      database.getGrantManager().addGrant(
           Privileges.PROCEDURE_ALL_PRIVS, GrantManager.TABLE,
           seq_name.toString(), user.getUserName(), true,
           Database.INTERNAL_SECURE_USERNAME);

    }
    else if (type.equals("drop")) {

      // Does the user have privs to create this sequence generator?
      if (!database.getDatabase().canUserDropSequenceObject(context,
                                                            user, seq_name)) {
        throw new UserAccessException(
                        "User not permitted to drop sequence: " + seq_name);
      }

      database.dropSequenceGenerator(seq_name);

      // Drop the grants for this object
      database.getGrantManager().revokeAllGrantsOnObject(
                                    GrantManager.TABLE, seq_name.toString());

    }
    else {
      throw new RuntimeException("Unknown type: " + type);
    }

    // Return an update result table.
    return FunctionTable.resultTable(context, 0);

  }

}