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Re^3: dbicdump and relationships

by zwon (Monsignor)
on Jan 14, 2013 at 15:01 UTC ( #1013229=note: print w/ replies, xml ) Need Help??


in reply to Re^2: dbicdump and relationships
in thread dbicdump and relationships

I see that DBIx::Class::Schema::Loader::DBI::mysql uses SHOW CREATE TABLE to get table definition, and then looking for

CONSTRAINT ... FOREIGN KEY ... REFERENCES ...
to get information about foreign keys. I tried to create some tables in mysql and check the output of SHOW CREATE TABLES:
mysql> create table foo (id integer primary key, name varchar(10)); Query OK, 0 rows affected (0.01 sec) mysql> create table boo (id integer primary key, foo_id integer refere +nces foo(id)); Query OK, 0 rows affected (0.00 sec) mysql> create table bar (id integer primary key, foo_id integer, const +raint foo_id_fk foreign key (foo_id) references foo(id)); Query OK, 0 rows affected (0.00 sec) mysql> show create table boo; +-------+------------------------------------------------------------- +--------------------------------------------------------------------- +----------+ | Table | Create Table + + | +-------+------------------------------------------------------------- +--------------------------------------------------------------------- +----------+ | boo | CREATE TABLE `boo` ( `id` int(11) NOT NULL, `foo_id` int(11) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 | +-------+------------------------------------------------------------- +--------------------------------------------------------------------- +----------+ 1 row in set (0.00 sec) mysql> show create table bar; +-------+------------------------------------------------------------- +--------------------------------------------------------------------- +--------------------------------------------------------------------- +--------------------------------------------+ | Table | Create Table + + + | +-------+------------------------------------------------------------- +--------------------------------------------------------------------- +--------------------------------------------------------------------- +--------------------------------------------+ | bar | CREATE TABLE `bar` ( `id` int(11) NOT NULL, `foo_id` int(11) DEFAULT NULL, PRIMARY KEY (`id`), KEY `foo_id_fk` (`foo_id`), CONSTRAINT `foo_id_fk` FOREIGN KEY (`foo_id`) REFERENCES `foo` (`id` +) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 | +-------+------------------------------------------------------------- +--------------------------------------------------------------------- +--------------------------------------------------------------------- +--------------------------------------------+ 1 row in set (0.00 sec) mysql> drop table foo; ERROR 1217 (23000): Cannot delete or update a parent row: a foreign ke +y constraint fails mysql> drop table bar; Query OK, 0 rows affected (0.00 sec) mysql> drop table foo; Query OK, 0 rows affected (0.00 sec)

As you can see, it looks like mysql silently ignores references in your SQL statements and doesn't create foreign keys. I would say it is rather nasty behaviour, if it doesn't accept your syntax it should throw an error.


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Re^4: dbicdump and relationships
by blue_cowdawg (Monsignor) on Jan 14, 2013 at 15:13 UTC
        As you can see, it looks like mysql silently ignores references in your SQL statements and doesn't create foreign keys. I would say it is rather nasty behaviour, if it doesn't accept your syntax it should throw an error.

    I knew there was something I didn't like about MySQL. I don't think I have that issue with PostgreSQL. :-(


    Peter L. Berghold -- Unix Professional
    Peter -at- Berghold -dot- Net; AOL IM redcowdawg Yahoo IM: blue_cowdawg
      :) sqlt -f MySQL -t MySQL < in > out
      ... INDEX (`sector`), PRIMARY KEY (`subsector_id`), CONSTRAINT `subsector_fk` FOREIGN KEY (`density`) REFERENCES `densit +y` (`density_id`), CONSTRAINT `subsector_fk_1` FOREIGN KEY (`sector`) REFERENCES `secto +r` (`sector_id`) ) ENGINE=InnoDB; SET foreign_key_checks=1;
Re^4: dbicdump and relationships
by blue_cowdawg (Monsignor) on Jan 14, 2013 at 15:46 UTC

    OK after massively modifications to my tables this now works. I wonder if I would have run into the same issues with PostgreSQL?


    Peter L. Berghold -- Unix Professional
    Peter -at- Berghold -dot- Net; AOL IM redcowdawg Yahoo IM: blue_cowdawg

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