Programming the Perl DBI

Name

trace

Synopsis

$h->trace($trace_level);
$h->trace($trace_level, $trace_filename);

DBI trace information can be enabled for a specific handle (and any future children of that handle) by setting the trace level using the trace method.

Trace level 1 is best for a simple overview of what’s happening. Trace level 2 is a good choice for general-purpose tracing. Levels 3 and above (up to 9) are best reserved for investigating a specific problem, when you need to see “inside” the driver and DBI. Set $trace_level to 0 to disable the trace.

The trace output is detailed and typically very useful. Much of the trace output is formatted using the neat function, so strings may be edited and truncated.

Initially, trace output is written to STDERR. If $trace_filename is specified, then the file is opened in append mode and all trace output (including that from other handles) is redirected to that file. Further calls to trace without a $trace_filename do not alter where the trace output is sent. If $trace_filename is undefined, then trace output is sent to STDERR and the previous trace file is closed.

See also the DBI->trace method for information about the DBI_TRACE environment variable.