[tarantool-patches] Re: [PATCH 0/5] Move FK constraints to server

[Kirill Yukhin <kyukhin@tarantool.org>]

Hello,
On 13 июл 05:04, Nikita Pettik wrote:
> Branch: https://github.com/tarantool/tarantool/commits/np/move-fk-to-server
> Issue: https://github.com/tarantool/tarantool/issues/3271
> 
> The aim of this patch-set is to move foreign key constraint to server
> and them be closer to ANSI specification.
> 
> First patch is preliminary and enables additional restrictions
> for FK constraints (ban opportunity to drop space referenced space,
> create FK referencing VIEW etc).
> 
> In original SQLite FK constraints may appear only during CREATE TABLE
> statement. Thus, it was enough to hold string of CREATE TABLE statement
> and reparse it once on instance loading. This approach defers all
> resolutions until FK usage. For instance:
> 
> CREATE TABLE t1(id PRIMARY KEY REFERENCES t2);
> CREATE TABLE t2(id PRIMARY KEY);
> 
> We decided to use another approach - where FK constraints are always consistent
> and all DD links are kept up. For instance, if we attempted to satisfy all
> restrictions using SQLite schema - we wouldn't be able to create circular
> dependencies. To support circular dependecies, we must allow to create them
> after space itself. In turn, to create FK constraints outside CREATE STATEMENT,
> we must persist them.  To implement these steps, firstly _fk_constraint system
> space is added - it contains tuples describing FK. Then, separate SQL statement
> <ALTER TABLE name ADD CONSTRAINT ...> is introduced which processes insertion
> and deletion from this space. Finally, FK processing has been refactored to
> rely on new DD in server (struct fkey and struct fkey_def). It seems that
> perfomance of FK handling has become a little bit better: now we don't need
> find suitable index on each FK invocation - its id is held into FK struct
> itself.
> 
> The last patch is simple follow-up which removes obsolete define guard
> for FK constraints.
> 
> Nikita Pettik (5):
>   sql: prohibit creation of FK on unexisting tables
>   schema: add new system space for FK constraints
>   sql: introduce ADD CONSTRAINT statement
>   sql: display error on FK creation and drop failure
>   sql: remove SQLITE_OMIT_FOREIGN_KEY define guard
I've checked the whole patchset into 2.0 branch.

--
Regards, Kirill Yukhin