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 ...
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