Hi,
WRT this bug entry http://code.google.com/p/ruby-sequel/issues/detail?id=317
I thought a primary key with multiple columns is more like an index
not a constraint.
When I add it to postgresql I get this....
Table "public.fn_call"
Column | Type | Modifiers
--------------+-----------------------------+-----------
user_id | integer | not null
store | character varying(32) | not null
object | character varying(32) | not null
fn | character varying(64) | not null
args | text |
priority | integer |
date_updated | timestamp without time zone |
Indexes:
"fn_call_pkey" PRIMARY KEY, btree (user_id, store, "object", fn)
Foreign-key constraints:
"fn_call_user_id_fkey" FOREIGN KEY (user_id) REFERENCES users(id)
and in mysql...
ysql> show index from fn_call;
+---------+------------+----------+--------------+-------------
+-----------+-------------+----------+--------+------+------------
+---------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name |
Collation | Cardinality | Sub_part | Packed | Null | Index_type |
Comment |
+---------+------------+----------+--------------+-------------
+-----------+-------------+----------+--------+------+------------
+---------+
| fn_call | 0 | PRIMARY | 1 | user_id |
A | NULL | NULL | NULL | | BTREE
| |
| fn_call | 0 | PRIMARY | 2 | store |
A | NULL | NULL | NULL | | BTREE
| |
| fn_call | 0 | PRIMARY | 3 | object |
A | NULL | NULL | NULL | | BTREE
| |
| fn_call | 0 | PRIMARY | 4 | fn |
A | 0 | NULL | NULL | | BTREE
| |
+---------+------------+----------+--------------+-------------
+-----------+-------------+----------+--------+------+------------
+---------+
4 rows in set (0.00 sec)
Which seems to show it as an index not a constraint, so if we have a
drop_index wouldn't drop_primary_key make sense?
I moved the discussion here so someone can explain to me why a multi
primary key is a constraint and not an index, seems to me it is
identical to a unique index?
Once I understand I would be happy to submit a patch to add
drop_primary_key [:one, :two, :three] (I have submitted several of the
alter_table patches in the past, actually I think I added the
constraint migrations :)
However I think it would be dangerous to allow it to drop a primary
key that was an autoindex column. I'd want it to just drop the index
not the column.
Thanks
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