[tarantool-patches] Re: [PATCH v2 1/5] sql: introduce structs assembling DDL arguments during parsing

[Vladislav Shpilevoy <v.shpilevoy@tarantool.org>]

On 27/03/2019 16:00, n.pettik wrote:
> 
> 
>> On 26 Mar 2019, at 21:06, Vladislav Shpilevoy <v.shpilevoy@tarantool.org> wrote:
>>
>> Thanks for the fixes! This commit LGTM.
>> Lets proceed to the next patches, and start
>> with a rebase, which is going to be hard.
> 
> Ok. Then I would like to clarify some details to avoid wasting time.
> In previous patch version, I used next (reworked) grammar to add
> FK constraints using ALTER:
> 
> cmd ::= alter_table_start alter_table_action .
> 
> alter_table_start ::= ALTER TABLE fullname(Z) . (1)
> 
> alter_table_action ::= add_constraint_def.
> alter_table_action ::= drop_constraint_def.
> alter_table_action ::= rename.
> 
> add_constraint_def ::= add_constraint_start constraint_def.
> 
> add_constraint_start(N) ::= ADD CONSTRAINT nm(Z). (2)
> constraint_def ::= foreign_key_def.
> 
> foreign_key_def ::= FOREIGN KEY LP eidlist(FA) RP REFERENCES nm(T)
>                        eidlist_opt(TA) matcharg(M) refargs(R) defer_subclause_opt(D).
> 
> Now obviously I can’t use it since foreign_key_def should call
> create_fk_def_init() which in turn requires table name and name
> of constraint defined in rules (1) and (2).
> 
> Why I want to use grammar mentioned above: it allows to remove
> code duplication. Rules to parse constraints are defined three times:
> 
> 1. ccons rule - that is part of column definition: …, a INT REFERENCES t1);
> 2. tcons rule - that is part of CREATE TABLE: …, CONSTRAINT c FOREIGN KEY …);
> 3. ALTER TABLE statement
> 
> All of them use the same grammar to parse statement starting from
> REFERENCES keyword. The same applies to UNIQUE and CHECK
> constraints. 
> 
> IDK how to avoid using alter_entity_def_init() and create_constraint_def_init()
> and at the same time divide constraint definition into several stages.
> 
> Ofc, we can still use simple approach like:
> 
> cmd ::= ALTER TABLE fullname(Z) ADD CONSTRAINT nm(Z)  FOREIGN KEY
>              LP eidlist(FA) RP REFERENCES nm(T) eidlist_opt(TA) matcharg(M)
>              refargs(R) defer_subclause_opt(D)
> 
> cmd ::= ALTER TABLE fullname(Z) ADD CONSTRAINT nm(Z)  UNIQUE
>              LP sortlist(X) RP
> 
> cmd ::= ALTER TABLE fullname(Z) ADD CONSTRAINT nm(Z)  PRIMARY KEY
>              LP sortlist(X) RP
> 
> cmd ::= ALTER TABLE fullname(Z) ADD CONSTRAINT nm(Z) CHECK …
> 
> cmd ::= ALTER TABLE fullname(Z) RENAME TO nm(N) .
> 
> Is this OK?
> 

Obviously, it is not. Why can't you define this?

alter_table_start(T) ::= ALTER TABLE fullname(T)
alter_add_constraint(T, N) ::= alter_table_start(T) ADD CONSTRAINT nm(N).

cmd ::= alter_add_constraint(T, N) FOREIGN KEY ...
cmd ::= alter_add_constraint(T, N) UNIQUE LP sortlist(X) RP
cmd ::= alter_add_constraint(T, N) PRIMARY KEY LP sortlist(X) RP
cmd ::= alter_add_constraint(T, N) CHECK ...
cmd ::= alter_table_start RENAME TO nm(N) .

Then inside each cmd you have both table and constraint names.