ai7ch / lib_fsm Goto Github PK

• must be a verb

• verb tense must be either at the simple past (+ed) or at present progressive (+ing)

• lower-case

• snake_case if multiple words (e.g. locked_out)

Examples: opened, loading, loaded, recorded, closed, locked, dumped, shipped, finished, running, failed, entered, enabled, disabled, approved, published, archived, activated, pending, pending_renewal, expired, ordered, canceled, returned, refunded, checked_out

• should be a single word (use snake_case otherwise)

• must be a verb

• verb tense must be infinitive

• lower-case

Examples: start, open, close, lock, unlock, load, unload, dump, ship, fail, enter, enable, disable, run, return, order, cancel, refund, confirm

Why did they do that?

I would not have done this way

A trigger on every tables that listen to the table state column and that have a custom type like lib_fsm.state_machine to know it must be monitored.

• Cons:

  • Custom types in PostgreSQL requires a C extension

  • C extensions are not supported in PostgreSQL managed environments

Rejected.

The previous idea but instead of a custom type, we rely on a composite type (last_state, abstract_machine__id).

• Pros:

  • Easier to maintain

  • Does not need column names convention

• Cons:

  • No foreign key on abstract_machine__id (ensure referential integrity with a trigger)

  • No foreign key on abstract_machine__id (ensuring referential integrity with a trigger would require a schema introspection to retrieve all columns of type lib_fsm.state_machine.abstract_machine\__id === old.abstract_machine__id)

Rejected.

Externalize each machine current states to an independent table. Each state is linked to a finite state machine (see abstract state machine).

• Pros:

  • The table schema explicitly states that one of more columns are each linked to their state machine

  • Supports multiple state (e.g. a contract might two columns, a signed_status and a writing_status)

• Cons:

  • Looking at a table, you don’t know the value of the current state (e.g. a contract status attribute). It requires an extra join.