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Posted by Joseph Brenner on April 4, 2005, 12:33 pm
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I've written a module that I'm getting set to upload to CPAN,
but I'd like to write some decent tests for it first.
The module is probably going to be called "GraphViz::DBI::General" [1].
What the module does is let you automatically generate a graph of
table relationships given a DBI database handle. This poses a
few problems for testing, one of which is that the data to be
plotted is table relationships, not something simple like the
contents of a table. MockDBI and SQLite are probably out of the
question.
But what's the alternative? Check for the availability of a real
database (somehow), check that I've got the permissions to do
things like "CREATE DATABASE" (somehow), and do a full blown run?
Any suggestions?
[1] My "GraphViz::DBI::General" is a subclass of the existing
"GraphViz::DBI" which is intended to work with a wider range of
databases. In particular Postgresql, for which "GraphViz::DBI" is
pretty useless (it has no concept of schemas). Also the original
module relies on a naming convention to find foreign keys, and I
prefer the DBI method "foreign_key_info" (even if it is labeled
"experimental").
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Posted by Ron Savage on April 5, 2005, 9:25 pm
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On Tue, 5 Apr 2005 04:33:33 +1000, Joseph Brenner wrote:
Hi Joseph
> [1] My "GraphViz::DBI::General" is a subclass of the existing
> "GraphViz::DBI" which is intended to work with a wider range of
> databases. In particular Postgresql, for which "GraphViz::DBI" is
> pretty useless (it has no concept of schemas). Also the original
> module relies on a naming convention to find foreign keys, and I
> prefer the DBI method "foreign_key_info" (even if it is labeled
> "experimental").
Is this of any relevance:
http://savage.net.au/Ron/html/graphing-database-schema.html
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Posted by Joseph Brenner on April 5, 2005, 6:23 pm
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> Joseph Brenner wrote:
>> [1] My "GraphViz::DBI::General" is a subclass of the existing
>> "GraphViz::DBI" which is intended to work with a wider range of
>> databases. In particular Postgresql, for which "GraphViz::DBI" is
>> pretty useless (it has no concept of schemas). Also the original
>> module relies on a naming convention to find foreign keys, and I
>> prefer the DBI method "foreign_key_info" (even if it is labeled
>> "experimental").
>
> Is this of any relevance:
http://savage.net.au/Ron/html/graphing-database-schema.html
Well, it's not *irrelevant*, but I see that you're take on the
problem just uses a *different* naming convention for foreign
keys:
The default implementation of GraphViz::DBI assumes that for a
column called t_id, then it is a foreign key if t is the name
of a table. This does not match my convention, so I wrote a
replacement for the sub, which uses my own table and column
naming convention to determine if a column is in fact a
foreign key. That convention is documented elsewhere. See
below for the link.
My take is that now that there's a DBI method that you can use to
get info about foreign keys, it's better to use that so the code
will work with any naming convention. And won't break if you
decide to deviate from the naming convention...
For example, I like the convention of using the table name as
the foreign key name (so my WHERE clauses look like
"person = person.id"). But what if I decide to create a
"freinds" table, that links together records in my person
table in pairs?
CREATE TABLE friends (
id SERIAL PRIMARY KEY,
person_1 REFERENCES person(id),
person_2 REFERENCES person(id)
);
Then I can't rigorously stick to the naming convention. I think
that's probably the case for most such naming conventions.
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