[Tarantool-patches] [PATCH 6/6] sql: extend result set with alias

[Nikita Pettik]

On 28 Nov 23:41, Vladislav Shpilevoy wrote:
> Thanks for the patch!
> 
> On 27/11/2019 13:15, Nikita Pettik wrote:
> > Each column of result set can feature its name alias. For instance:
> > 
> > SELECT x + 1 AS add FROM ...;
> > 
> > In this case real name of resulting set column is "x + 1" meanwhile
> > "add" is its alias. This patch extends metadata with optional metadata
> > member which corresponds to column's alias.
> 
> I was always thinking that the alias should be returned as a
> name. And the real name should be returned as meta. And looks
> like it is so:
> 
>     tarantool> box.execute('SELECT 1 AS kek')
>     ---
>     - metadata:
>       - name: KEK
>         type: integer
>       rows:
>       - [1]
>     ...
> 
> That makes me think we should not break it. And
> meta should return the real name in case there is
> an alias. Because otherwise the aliases are useless
> in meta.

(ANSI parts which concern Java and CLI are quite complicated to read
 and understand, so I refer to Oracle docs).

https://docs.oracle.com/javase/8/docs/api/java/sql/ResultSetMetaData.html#getColumnLabel-int-

'The suggested title is usually specified by the SQL AS clause.'

https://stackoverflow.com/questions/4271152/getcolumnlabel-vs-getcolumnname

I assume that :getColumnLabel() returns name of label, not real name
(at least it seems to be rational).
 
> Btw the example above is executed on this commit. So
> now the results are inconsistent. Some queries return
> alias in 'name'. Some return a real name in 'name'. I
> think we should keep it as was, and return alias in
> 'name'.

Sorry, now it is fixed:

- metadata:
  - type: integer
    name: '1'
    alias: KEK
  rows:
  - [1]
...

I've extended commit message with doc bot request:

    sql: extend result set with alias
    
    Each column of result set can feature its name alias. For instance:
    
    SELECT x + 1 AS add FROM ...;
    
    In this case real name of resulting set column is "x + 1" meanwhile
    "add" is its alias. This patch extends metadata with optional metadata
    member which corresponds to column's alias.
    
    Closes #4407
    
    @TarantoolBot document
    Title: extended SQL metadata
    
    Before this patch metadata for SQL DQL contained only two fields:
    name and type of each column of result set. Now it may contain
    following properties:
     - collation (in case type of resulting set column is string and
                  collation is different from default "none");
       is encoded with IPROTO_FIELD_COLL key in IPROTO_METADATA map;
     - is_nullable (in case column of result set corresponds to space's
                    field; for expressions like x+1 for the sake of
                    simplicity nullability is omitted);
       is encoded with IPROTO_FIELD_IS_NULLABLE key in IPROTO_METADATA;
     - is_autoincrement (is set only for autoincrement column in result
                         set);
       is encoded with IPROTO_FIELD_IS_AUNTOINCREMENT key in IPROTO_METADATA;
     - alias (if column of result set is specified with AS label);
       is encoded with IPROTO_FIELD_ALIAS key in IPROTO_METADATA map.