MySQL Cookbook

Determining Which Table Types the Server Supports

Problem

You want to know whether you can create a table using a given table type.

Solution

Ask the server which table types it supports.

Discussion

SHOW VARIABLES can tell you whether or not certain table types are available. For example, you can test the have_bdb, have_innodb, and have_gemini variables to see if the server supports transaction-safe tables. The following PHP code demonstrates how to check for a value of YES for the have_bdb variable, using a two-stage approach. First, make sure that the variable exists by testing for a nonempty result set. (The variable will not be present at all if your version of MySQL predates the inclusion of support for the table type.) Then, fetch the variable’s value to see if it’s YES:

$avail = FALSE;
# escape the variable name properly
$var_name = ereg_replace ("([%_])", "\\\\1", "have_bdb");
if ($result_id = mysql_query ("SHOW VARIABLES LIKE '$var_name'", $conn_id))
{
    if ($row = mysql_fetch_row ($result_id))
        $avail = ($row[1] == "YES" ? TRUE : FALSE);
    mysql_free_result ($result_id);
}

After this code executes, $avail will be TRUE or FALSE to indicate whether the server supports BDB tables. To check for a different table type, modify the code to test the appropriate server variable name.

A more general approach is to write a function that checks for all known handlers and returns a list of the ones that are supported. You cannot ask the server for a list of types directly, but if you know what ...