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RowDataCursor.java

/*
 Copyright (c) 2002, 2010, Oracle and/or its affiliates. All rights reserved.
 

  The MySQL Connector/J is licensed under the terms of the GPLv2
  <http://www.gnu.org/licenses/old-licenses/gpl-2.0.html>, like most MySQL Connectors.
  There are special exceptions to the terms and conditions of the GPLv2 as it is applied to
  this software, see the FLOSS License Exception
  <http://www.mysql.com/about/legal/licensing/foss-exception.html>.

  This program is free software; you can redistribute it and/or modify it under the terms
  of the GNU General Public License as published by the Free Software Foundation; version 2
  of the License.

  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 for more details.

  You should have received a copy of the GNU General Public License along with this
  program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth
  Floor, Boston, MA 02110-1301  USA
 */

package com.mysql.jdbc;

import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

/**
 * Model for result set data backed by a cursor. Only works for forward-only
 * result sets (but still works with updatable concurrency).
 * 
 * @version $Id: CursorRowProvider.java,v 1.1.2.1 2005/05/19 18:31:49 mmatthews
 *          Exp $
 */
00037 public class RowDataCursor implements RowData {

      private final static int BEFORE_START_OF_ROWS = -1;

      /**
       * The cache of rows we have retrieved from the server.
       */
00044       private List fetchedRows;

      /**
       * Where we are positionaly in the entire result set, used mostly to
       * facilitate easy 'isBeforeFirst()' and 'isFirst()' methods.
       */
00050       private int currentPositionInEntireResult = BEFORE_START_OF_ROWS;

      /**
       * Position in cache of rows, used to determine if we need to fetch more
       * rows from the server to satisfy a request for the next row.
       */
00056       private int currentPositionInFetchedRows = BEFORE_START_OF_ROWS;

      /**
       * The result set that we 'belong' to.
       */
00061       private ResultSetImpl owner;

      /**
       * Have we been told from the server that we have seen the last row?
       */
00066       private boolean lastRowFetched = false;

      /**
       * Field-level metadata from the server. We need this, because it is not
       * sent for each batch of rows, but we need the metadata to unpack the
       * results for each field.
       */
00073       private Field[] metadata;

      /**
       * Communications channel to the server
       */
00078       private MysqlIO mysql;

      /**
       * Identifier for the statement that created this cursor.
       */
00083       private long statementIdOnServer;

      /**
       * The prepared statement that created this cursor.
       */
00088       private ServerPreparedStatement prepStmt;

      /**
       * The server status for 'last-row-sent'...This might belong in mysqldefs,
       * but it it only ever referenced from here.
       */
00094       private static final int SERVER_STATUS_LAST_ROW_SENT = 128;

      /**
       * Have we attempted to fetch any rows yet?
       */
00099       private boolean firstFetchCompleted = false;

      private boolean wasEmpty = false;

      private boolean useBufferRowExplicit = false;
      
      /**
       * Creates a new cursor-backed row provider.
       * 
       * @param ioChannel
       *            connection to the server.
       * @param creatingStatement
       *            statement that opened the cursor.
       * @param metadata
       *            field-level metadata for the results that this cursor covers.
       */
00115       public RowDataCursor(MysqlIO ioChannel,
                  ServerPreparedStatement creatingStatement, Field[] metadata) {
            this.currentPositionInEntireResult = BEFORE_START_OF_ROWS;
            this.metadata = metadata;
            this.mysql = ioChannel;
            this.statementIdOnServer = creatingStatement.getServerStatementId();
            this.prepStmt = creatingStatement;
            this.useBufferRowExplicit = MysqlIO.useBufferRowExplicit(this.metadata);
            
      }

      /**
       * Returns true if we got the last element.
       * 
       * @return DOCUMENT ME!
       */
00131       public boolean isAfterLast() {
            return lastRowFetched
                        && this.currentPositionInFetchedRows > this.fetchedRows.size();
      }

      /**
       * Only works on non dynamic result sets.
       * 
       * @param index
       *            row number to get at
       * @return row data at index
       * @throws SQLException
       *             if a database error occurs
       */
00145       public ResultSetRow getAt(int ind) throws SQLException {
            notSupported();

            return null;
      }

      /**
       * Returns if iteration has not occured yet.
       * 
       * @return true if before first row
       * @throws SQLException
       *             if a database error occurs
       */
00158       public boolean isBeforeFirst() throws SQLException {
            return this.currentPositionInEntireResult < 0;
      }

      /**
       * Moves the current position in the result set to the given row number.
       * 
       * @param rowNumber
       *            row to move to
       * @throws SQLException
       *             if a database error occurs
       */
00170       public void setCurrentRow(int rowNumber) throws SQLException {
            notSupported();
      }

      /**
       * Returns the current position in the result set as a row number.
       * 
       * @return the current row number
       * @throws SQLException
       *             if a database error occurs
       */
00181       public int getCurrentRowNumber() throws SQLException {
            return this.currentPositionInEntireResult + 1;
      }

      /**
       * Returns true if the result set is dynamic.
       * 
       * This means that move back and move forward won't work because we do not
       * hold on to the records.
       * 
       * @return true if this result set is streaming from the server
       */
00193       public boolean isDynamic() {
            return true;
      }

      /**
       * Has no records.
       * 
       * @return true if no records
       * @throws SQLException
       *             if a database error occurs
       */
00204       public boolean isEmpty() throws SQLException {
            return this.isBeforeFirst() && this.isAfterLast();
      }

      /**
       * Are we on the first row of the result set?
       * 
       * @return true if on first row
       * @throws SQLException
       *             if a database error occurs
       */
00215       public boolean isFirst() throws SQLException {
            return this.currentPositionInEntireResult == 0;
      }

      /**
       * Are we on the last row of the result set?
       * 
       * @return true if on last row
       * @throws SQLException
       *             if a database error occurs
       */
00226       public boolean isLast() throws SQLException {
            return this.lastRowFetched
                        && this.currentPositionInFetchedRows == (this.fetchedRows
                                    .size() - 1);
      }

      /**
       * Adds a row to this row data.
       * 
       * @param row
       *            the row to add
       * @throws SQLException
       *             if a database error occurs
       */
00240       public void addRow(ResultSetRow row) throws SQLException {
            notSupported();
      }

      /**
       * Moves to after last.
       * 
       * @throws SQLException
       *             if a database error occurs
       */
00250       public void afterLast() throws SQLException {
            notSupported();
      }

      /**
       * Moves to before first.
       * 
       * @throws SQLException
       *             if a database error occurs
       */
00260       public void beforeFirst() throws SQLException {
            notSupported();
      }

      /**
       * Moves to before last so next el is the last el.
       * 
       * @throws SQLException
       *             if a database error occurs
       */
00270       public void beforeLast() throws SQLException {
            notSupported();
      }

      /**
       * We're done.
       * 
       * @throws SQLException
       *             if a database error occurs
       */
00280       public void close() throws SQLException {

            this.metadata = null;
            this.owner = null;
      }

      /**
       * Returns true if another row exists.
       * 
       * @return true if more rows
       * @throws SQLException
       *             if a database error occurs
       */
00293       public boolean hasNext() throws SQLException {

            if (this.fetchedRows != null && this.fetchedRows.size() == 0) {
                  return false;
            }

            if (this.owner != null && this.owner.owningStatement != null) {
                  int maxRows = this.owner.owningStatement.maxRows;
                  
                  if (maxRows != -1 && this.currentPositionInEntireResult + 1 > maxRows) {
                        return false;
                  }     
            }
            
            if (this.currentPositionInEntireResult != BEFORE_START_OF_ROWS) {
                  // Case, we've fetched some rows, but are not at end of fetched
                  // block
                  if (this.currentPositionInFetchedRows < (this.fetchedRows.size() - 1)) {
                        return true;
                  } else if (this.currentPositionInFetchedRows == this.fetchedRows
                              .size()
                              && this.lastRowFetched) {
                        return false;
                  } else {
                        // need to fetch to determine
                        fetchMoreRows();

                        return (this.fetchedRows.size() > 0);
                  }
            }

            // Okay, no rows _yet_, so fetch 'em

            fetchMoreRows();

            return this.fetchedRows.size() > 0;
      }

      /**
       * Moves the current position relative 'rows' from the current position.
       * 
       * @param rows
       *            the relative number of rows to move
       * @throws SQLException
       *             if a database error occurs
       */
00339       public void moveRowRelative(int rows) throws SQLException {
            notSupported();
      }

      /**
       * Returns the next row.
       * 
       * @return the next row value
       * @throws SQLException
       *             if a database error occurs
       */
00350       public ResultSetRow next() throws SQLException {
            if (this.fetchedRows == null && this.currentPositionInEntireResult != BEFORE_START_OF_ROWS) {
                  throw SQLError.createSQLException(
                              Messages
                                          .getString("ResultSet.Operation_not_allowed_after_ResultSet_closed_144"), //$NON-NLS-1$
                              SQLError.SQL_STATE_GENERAL_ERROR, mysql.getExceptionInterceptor());
            }
            
            if (!hasNext()) {
                  return null;
            }
            
            this.currentPositionInEntireResult++;
            this.currentPositionInFetchedRows++;

            // Catch the forced scroll-passed-end
            if (this.fetchedRows != null && this.fetchedRows.size() == 0) {
                  return null;
            }

            if (this.currentPositionInFetchedRows > (this.fetchedRows.size() - 1)) {
                  fetchMoreRows();
                  this.currentPositionInFetchedRows = 0;
            }

            ResultSetRow row = (ResultSetRow) this.fetchedRows
                        .get(this.currentPositionInFetchedRows);

            row.setMetadata(this.metadata);
            
            return row;
      }

      /**
       * 
       */
      private void fetchMoreRows() throws SQLException {
            if (this.lastRowFetched) {
                  this.fetchedRows = new ArrayList(0);
                  return;
            }

            synchronized (this.owner.connection) {
                  boolean oldFirstFetchCompleted = this.firstFetchCompleted;
                  
                  if (!this.firstFetchCompleted) {
                        this.firstFetchCompleted = true;
                  }

                  int numRowsToFetch = this.owner.getFetchSize();

                  if (numRowsToFetch == 0) {
                        numRowsToFetch = this.prepStmt.getFetchSize();
                  }
                  
                  if (numRowsToFetch == Integer.MIN_VALUE) {
                        // Handle the case where the user used 'old'
                        // streaming result sets

                        numRowsToFetch = 1;
                  }

                  this.fetchedRows = this.mysql.fetchRowsViaCursor(this.fetchedRows,
                              this.statementIdOnServer, this.metadata, numRowsToFetch, 
                              this.useBufferRowExplicit);
                  this.currentPositionInFetchedRows = BEFORE_START_OF_ROWS;

                  if ((this.mysql.getServerStatus() & SERVER_STATUS_LAST_ROW_SENT) != 0) {
                        this.lastRowFetched = true;
                        
                        if (!oldFirstFetchCompleted && this.fetchedRows.size() == 0) {
                              this.wasEmpty  = true;
                        }
                  }
            }
      }

      /**
       * Removes the row at the given index.
       * 
       * @param index
       *            the row to move to
       * @throws SQLException
       *             if a database error occurs
       */
00435       public void removeRow(int ind) throws SQLException {
            notSupported();
      }

      /**
       * Only works on non dynamic result sets.
       * 
       * @return the size of this row data
       */
00444       public int size() {
            return RESULT_SET_SIZE_UNKNOWN;
      }

      private void nextRecord() throws SQLException {

      }

      private void notSupported() throws SQLException {
            throw new OperationNotSupportedException();
      }

      /*
       * (non-Javadoc)
       * 
       * @see com.mysql.jdbc.RowProvider#setOwner(com.mysql.jdbc.ResultSet)
       */
00461       public void setOwner(ResultSetImpl rs) {
            this.owner = rs;
      }

      /*
       * (non-Javadoc)
       * 
       * @see com.mysql.jdbc.RowProvider#getOwner()
       */
00470       public ResultSetInternalMethods getOwner() {
            return this.owner;
      }

00474       public boolean wasEmpty() {
            return this.wasEmpty;
      }
      
00478       public void setMetadata(Field[] metadata) {
            this.metadata = metadata;
      }

}

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