Re: [Tarantool-patches] [PATCH] box: remove unicode_ci for functions

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

Hi, thanks for the review!

On 30/11/2019 21:34, Konstantin Osipov wrote:
> * Chris Sosnin <k.sosnin@tarantool.org> [19/11/30 07:03]:
>> Unicode_ci collation breaks the general
>> rule for objects naming, so we remove it
>> in version 2.3.1
> 
> The code works according to RFC.
> 
> There is a justification for this behaviour in RFC.
> 
> 

Yeah, RFC is cool and all, but 'this is in an RFC' is not
a good justification, don't you think? Especially taking
into account, that this is our own RFC. It is not a
standard or something.

With Chris we did a little investigation, and here is what
we've found:

- The RFC does not explain why we need a case-insensitive
  index. This has nothing to do with conflicts. SQL always
  is and will be able to choose one name - the uppercased
  one;

- Despite the index is case insensitive, I still get an error
  when call a not uppercased function from SQL:

      box.cfg{}
      box.schema.func.create('func1', {language = 'Lua', is_deterministic = true,
                                       body = 'function(a) return a end',
                                       param_list = {'any'}, returns = 'string',
                                       exports = {'LUA', 'SQL'}})
      box.execute('SELECT func1(\'str\')')
      ---
      - null
      - Function 'FUNC1' does not exist
      ...

      box.execute('SELECT "func1"(\'str\')')
      ---
      - metadata:
        - name: '"func1"(''str'')'
          type: string
        rows:
        - ['str']
      ...

  As you can see, the index's case does not matter. It is
  insensitive, but I still need to write functions in a
  special register.

- Lua box.func.* is also case sensitive:

      tarantool> box.schema.func.create('func1')
      ---
      ...

      tarantool> box.schema.func.create('FUNC1')
      ---
      - error: Function 'FUNC1' already exists
      ...

      tarantool> box.func['FUNC1']
      ---
      - null
      ...

  The error message is really confusing. It says, that
  such a function already exists, but nonetheless I can't
  get it. This is ridiculous.

- As Peter said, _func behaves inconsistent with all the
  other system spaces.

- As Peter said, we did it just for SQL, but it affects
  non-SQL front ends. As you can see from the box.func.*
  example.

On the summary, this collation is clearly useless - its
case insensitivity does not help any of the listed problems.
Therefore, it is a bug.

I think the collation should be dropped.