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  package org.apache.cayenne.access.jdbc;
  
  import java.sql.ResultSet;
  import java.sql.SQLException;
  import java.util.List;
  
  import org.apache.cayenne.access.DataNode;
  import org.apache.cayenne.access.OperationObserver;
  import org.apache.cayenne.access.jdbc.reader.RowReader;
  import org.apache.cayenne.query.Query;
  import org.apache.cayenne.query.QueryMetadata;
  import org.apache.cayenne.query.SQLAction;
  
  /**
   * A convenience superclass for SQLAction implementations.
   * 
   * @since 1.2
   */
  public abstract class BaseSQLAction implements SQLAction {
  
      protected DataNode dataNode;
  
      /**
       * @since 4.0
       */
      public BaseSQLAction(DataNode dataNode) {
          this.dataNode = dataNode;
      }
  
      /**
       * Helper method to process a ResultSet.
       */
      @SuppressWarnings({ "rawtypes", "unchecked" })
      protected void readResultSet(ResultSet resultSet, RowDescriptor descriptor, Query query, OperationObserver delegate)
              throws SQLException, Exception {
  
          long t1 = System.currentTimeMillis();
  
          QueryMetadata metadata = query.getMetaData(dataNode.getEntityResolver());
  
          RowReader<?> rowReader = dataNode.rowReader(descriptor, metadata);
  
          JDBCResultIterator resultReader = new JDBCResultIterator(null, resultSet, rowReader);
  
          LimitResultIterator it = new LimitResultIterator(resultReader, getInMemoryOffset(metadata.getFetchOffset()),
                  metadata.getFetchLimit());
  
          if (!delegate.isIteratedResult()) {
              List resultRows = it.allRows();
              dataNode.getJdbcEventLogger().logSelectCount(resultRows.size(), System.currentTimeMillis() - t1);
  
              delegate.nextRows(query, resultRows);
          } else {
              try {
                  delegate.nextRows(query, it);
              } catch (Exception ex) {
                  it.close();
                  throw ex;
              }
          }
      }
  
      /**
       * Returns a value of the offset that will be used to rewind the ResultSet
       * within the SQL action before reading the result rows. The default
       * implementation returns 'queryOffset' argument. If the adapter supports
       * setting offset at the SQL level, this method must be overridden to return
       * zero to suppress manual offset.
       * 
       * @since 3.0
       */
      protected int getInMemoryOffset(int queryOffset) {
          return queryOffset;
      }
  }
  