Supporting natural keys

[maiha]

This PR enhances Model.primary to accept auto option that works as a natural key if false.

Example (use RDB as KVS)

mysql> DESCRIBE kvss;
+-------+--------------+------+-----+---------+-------+
| Field | Type         | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| k     | varchar(255) | NO   | PRI | NULL    |       |
| v     | varchar(255) | YES  |     | NULL    |       |
+-------+--------------+------+-----+---------+-------+

class Kvs < Granite::ORM::Base
  adapter mysql
  primary k : String
  field   v : String
end

First, if you use a primary key other than Int as described above, it will give a compile error with following suggestion.

Failed to define Kvs#save: Primary key must be Int(32|64), or set `auto: false` for natural keys.

  primary k : String, auto: false

After adding auto: false that disables auto number feature, we can play with nartural keys.

class Kvs < Granite::ORM::Base
  adapter mysql
  primary k : String, auto: false
  field   v : String
end

## Create
port = Kvs.new(k: "mysql_port", v: "3306")
port.new_record? # => true
port.save        # => true
# INSERT INTO `kvs` (`v`, `k`) VALUES (?, ?): ["3306", "mysql_port"]
Kvs.count        # => 1

## Read
port = Kvs.find("mysql_port")
port.new_record? # => false
port.v           # => "3306"

## Update
port.v = "3307"
port.new_record? # => false
port.save        # => true
# UPDATE `kvs` SET `v`=? WHERE `k`=?: ["3307", "mysql_port"]

## Delete
port.destroy     # => true
Kvs.count        # => 0

Best regards,

[drujensen]

@maiha Excellent work! 💯

[Blacksmoke16]

port = Kvs.new(k: "mysql_port", v: "3306")
p port.inspect

"#<Kvs:0x5591aabc39c0 @new_record=true, @destroyed=false, @errors=[], @k=nil, @v=\"3306\", @updated_at=nil, @created_at=nil>"

@maiha
Shouldn't the k instance variable be set to "mysql_port" when inspecting the object?

[maiha]

Pushed -f to resolve conflicts.

[maiha]

@Blacksmoke16
Yep, I just added new with mass-assignment yesterday into this PR!
maiha:master + new(*mass-assignment*) → maiha:natural-key

If you are using maiha:master branch, could you try again with maiha:natural-key or this pr branch? This should work!

[Blacksmoke16]

Ah perfect! Was behind a few commits i guess :)

[drujensen]

👍

[robacarp]

@maiha thank you for this contribution