Re: Taking trace () to the next level ...

H.Merijn Brand wrote:
> I've had a series of discussions with several DBD authors and others
> because I wanted to get better support for Driver-side trace message
> handling in a portable way.
> 
> My DBD::Unify supports $dbh->{dbd_verbose} since a *long* time, and Tim
> never saw the generic value of that, but now that John Scoles has used
> it for himself in DBD::Oracle and others showed interest too, it might
> be well worth to take the discussion to a wider board.
> 
> Here's a summary, '»' marked lines are proposed additions/changes. I
> hope I interpreted all opinions correctly.
> 
> DBI
> 
> 	$h->trace ($trace_setting [, $output ]);
> 
>    $h may be 'DBI'
> 
>    $trace_setting is a (combined) flag, which supports
> 
> 	1..15	Simple debug level
> 	"SQL"	All SQL statements executed (not yet implemented)
> 	"ALL"	All DBI *and* Driver flags
> »	"DBD"	All Driver flags
> 
> »	   $h->trace ("DBD=7") could be an alternative to set the level
> 
> 	"1|pglib"	Combinations of a DBI debug level and driver
> 			flags, which have to be parsed by
> 			parse_trace_flags ()
> »	"1|4"		Combination of a DBI debug level and a
> 			driver debug level
> »	"|4"		Driver-side only debug level, will NOT
> 			alter the current DBI debug level
> 
> 	$trace_setting can be stored in $ENV{DBI_TRACE}
> »	Driver side $trace_settings can be stored in $ENV{DBD_TRACE}
> 	(note that this /was/ DBD_VERBOSE in previous discussions, but
> 	DBD_TRACE is more in line with the above)
> 
> 	#define DBIc_TRACE_LEVEL_MASK   0x0000000F
> 	#define DBIc_TRACE_FLAGS_MASK   0xFFFFFF00
> 
> 	Is 0x00000000F0 supposed to be the Driver *level* mask?
> 
>    $output can be a filename or an output handle. The latter is very
>    nice in combination with perlIO
> 
> 	my $trace = "";
> 	open my $th, ">", \$trace;
> 	$dbh->trace (4, $th);
> 	...
> 	$dbh->trace (0);
> 	# Trace log now in $trace;
> 
>    Handles can get there own (inherited) $trace_setting using the
> 
> 	$h->{TraceLevel}  = "2|14";
> »	$h->{dbd_verbose} = 4;
> 
> »  the dbd_verbose attribute is internally implemented as uni_verbose,
> »  pg_verbose, ora_verbose, ... but offers a generic alias to
> »  dbd_verbose, so that writing cross-database portable scripts will be
> »  much easier.
> 
> There is no policy regarding DBD tracing. DBD::Unify uses a trace
> *level*, which is by default inherited from dbis->debug (XS), but
> DBD::Pg uses flags
> 
> DBI - Uses trace *level* (flags SQL or ALL set all)
>   0 - Trace disabled.
>   1 - Trace top-level DBI method calls returning with results or errors.
>   2 - As above, adding tracing of top-level method entry with parameters.
>   3 - As above, adding some high-level information from the driver
>       and some internal information from the DBI.
>   4 - As above, adding more detailed information from the driver.
>       This is the first level to trace all the rows being fetched.
>   5 to 15 - As above but with more and more internal information.
> 
> DBD::Unify - Uses trace *level*
>   0 - Trace disabled
>   1 - No messages defined (yet)
>   2 - Level 1 plus main method entry and exit points:
>   3 - Level 2 plus errors and additional return codes and field types
>       and values:
>   4 - Level 3 plus some content info:
>   5 - Level 4 plus internal coding for exchanges and low(er) level
>       return codes:
>   6 - Level 5 plus destroy/cleanup states:
>   7 - No messages (yet) set to level 7 and up.
> 
> DBD::Oracle - Uses trace *level*
>   Uses level 1..6, but does not document what the output is
> 
> DBD::Pg - uses trace *flags* AND *level* from DBI. Level 4 or higher
> 	  sets all flags
>   pglibpq	- Outputs the name of each libpq function (without
> 		  arguments) immediately before running it.
>   pgstart	- Outputs the name of each internal DBD::Pg function,
> 		  and other information such as the function arguments
> 		  or important global variables, as each function starts
>   pgend		- Outputs a simple message at the very end of
> 		  each internal DBD::Pg function.
>   pgprefix	- Forces each line of trace output to begin with the
> 		  string "dbdpg: "
>   pglogin	- Outputs a message showing the connection string
> 		  right before a new database connection is attempted
> 		  (on with level 5 or up)
> 
> DBD::MySQL - Cannot find anything in the docs about tracing
> 
> DBD::ODBC - Only supports one trace flag
>   odbcdev	- flag is used to output development tracing so it
> 		  should not be relevant in normal use.
>   DBD::ODBC outputs tracing at levels 3 and above (as levels 1 and 2
>   are reserved for DBI).
> 
> Where is it stated that levels 1 and 2 are DBI only?
> 
> All of the people I talked to agree that is is often useful to see
> Driver-only tracing/debugging, as by now we do trust that DBI is Doing
> The Right Thing (TM)
> 
> The problem with the current definition of the trace_flags, is that,
> even though most drivers still work with a trace *level*, it only
> supports trace *flags*. My implementation and suggestion of
> $h->{dbd_verbose} is a nice workaround to start with, but it would be
> easier to lift it to the trace method, so that Driver-only tracing is
> more standardized
> 
> http://search.cpan.org/~timb/DBI-1.607/lib/DBI/DBD.pm#Other_database_handle_methods
> 

Did anything come of this thread - perhaps I missed the tail end of it.

I'd still like to produce DBD-specific tracing without DBI tracing so 
would be interested in any result.

Martin
-- 
Martin J. Evans
Easysoft Limited
http://www.easysoft.com