[tarantool-patches] Re: [PATCH 2/6] sql: rework ALTER TABLE grammar

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

Thanks for the patch! See 5 comments below.

On 09/01/2019 15:13, Nikita Pettik wrote:
> Since ALTER TABLE ADD CONSTRAINT can be used to add various constraint
> types (foreign key, unique etc), we should rework its grammar.

1. But you still can not add a unique constraint via ADD CONSTRAINT ...
The reworked grammar can be used for foreign keys only, until the last
commit.

> As a reference for it lets use one from ANSI.
> 
> Needed for #3097
> ---
>   src/box/sql/parse.y | 44 +++++++++++++++++++++++++++++---------------
>   1 file changed, 29 insertions(+), 15 deletions(-)
> 
> diff --git a/src/box/sql/parse.y b/src/box/sql/parse.y
> index f4fdf58f2..874a67a9b 100644
> --- a/src/box/sql/parse.y
> +++ b/src/box/sql/parse.y
> @@ -318,10 +318,8 @@ tcons ::= UNIQUE LP sortlist(X) RP.
>                                                      SQL_INDEX_TYPE_CONSTRAINT_UNIQUE);}
>   tcons ::= CHECK LP expr(E) RP onconf.
>                                    {sql_add_check_constraint(pParse,&E);}
> -tcons ::= FOREIGN KEY LP eidlist(FA) RP
> -          REFERENCES nm(T) eidlist_opt(TA) refargs(R) defer_subclause_opt(D). {
> -    sql_create_foreign_key(pParse, FA, &T, TA, D, R);
> -}
> +tcons ::= foreign_key_def.

2. Sorry for a nit, but I do not like _def for non-struct things. Why not
just foreign_key? For example, 'expr' rule is just 'expr', not 'expr_def'.
The same about other new _def prefixes here and in the last commit.

> +
>   %type defer_subclause_opt {int}
>   defer_subclause_opt(A) ::= .                    {A = 0;}
>   defer_subclause_opt(A) ::= defer_subclause(A).
> @@ -1444,22 +1442,38 @@ cmd ::= ANALYZE.                {sqlite3Analyze(pParse, 0);}
>   cmd ::= ANALYZE nm(X).          {sqlite3Analyze(pParse, &X);}
>   
>   //////////////////////// ALTER TABLE table ... ////////////////////////////////
> -cmd ::= ALTER TABLE fullname(X) RENAME TO nm(Z). {
> -  pParse->constraint->table_name = X;
> +cmd ::= alter_table_start alter_table_action .

3. The same. How about 'alter_table_action' -> 'alter_table'?
Also, as I understand, you did not inline alter_table_start here
because you need its C code be executed before alter_table_action,
right? Then how about a comment on it?

> +
> +alter_table_start ::= ALTER TABLE fullname(Z) . {
> +  pParse->constraint->table_name = Z;
> +  pParse->constraint->name.n = 0;
> +}
> +
> +alter_table_action ::= add_constraint_def.
> +alter_table_action ::= drop_constraint_def.
> +/** RENAME is ANSI extension, so it comes as a very special case. */
> +alter_table_action ::= rename.

4. It is an extension but why is it special? It is just one of
the ways of table alteration.

> +
> +rename ::= RENAME TO nm(Z). {
>     sql_alter_table_rename(pParse, &Z);
>   }
>   
> -cmd ::= ALTER TABLE fullname(X) ADD CONSTRAINT nm(Z) FOREIGN KEY
> -        LP eidlist(FA) RP REFERENCES nm(T) eidlist_opt(TA) refargs(R)
> -        defer_subclause_opt(D). {
> -    pParse->constraint->table_name = X;
> -    pParse->constraint->name = Z;
> -    sql_create_foreign_key(pParse, FA, &T, TA, D, R);
> +add_constraint_def ::= add_constraint_start constraint_def.
> +
> +add_constraint_start ::= ADD CONSTRAINT nm(Z). {
> +  pParse->constraint->name = Z;
>   }
>   
> -cmd ::= ALTER TABLE fullname(X) DROP CONSTRAINT nm(Z). {
> -    pParse->constraint->table_name = X;
> -    sql_drop_foreign_key(pParse, &Z);
> +constraint_def ::= foreign_key_def.
> +
> +foreign_key_def ::= FOREIGN KEY LP eidlist(FA) RP REFERENCES nm(T)
> +                    eidlist_opt(TA) refargs(R) defer_subclause_opt(D). {
> +  sql_create_foreign_key(pParse, FA, &T, TA, D, R);
> +}
> +
> +

5. Double empty-line.

> +drop_constraint_def ::= DROP CONSTRAINT nm(Z). {
> +  sql_drop_foreign_key(pParse, &Z);
>   }
>   
>   //////////////////////// COMMON TABLE EXPRESSIONS ////////////////////////////
>