JDBC provides a variety of methods to retrieve data from a result set, such as getInt, getString, and getObject. The getObject method is the most generic and provides the worst performance when the non-default mappings are specified. This is because the JDBC driver must do extra processing to determine the type of the value being retrieved and generate the appropriate mapping. Always use the specific method for the data type.
To further improve performance, provide the column number of the column being retrieved, for example, getString(1), getLong(2), and getInt(3), instead of the column name. If the column names are not specified, network traffic is unaffected, but costly conversions and lookups increase. For example, suppose you use:
getString("foo")...
The JDBC driver may have to convert foo to uppercase (if necessary), and then compare foo with all the columns in the column list. That is costly. If, instead, the driver was able to go directly to result column 23, then a lot of processing would be saved.
For example, suppose you have a result set that has 15 columns and 100 rows, and the column names are not included in the result set. You are interested in three columns, EMPLOYEENAME (a string), EMPLOYEENUMBER (a long integer), and SALARY (an integer). If you specify getString("EmployeeName"), getLong("EmployeeNumber"), and getInt("Salary"), each column name must be converted to uppercase, and lookups would increase considerably. Performance would improve significantly if you specify getString(1), getLong(2), and getInt(15).
