maria-developers team mailing list archive

[Sergei Golubchik <serg@xxxxxxxxxxx>]

Hi, Peter!

On Dec 30, Peter Laursen wrote:
> Compare "generated columns" in MySQL 5.7.5 labs (refer
> http://mysqlserverteam.com/generated-columns-in-mysql-5-7-5/).  It has
> instrumentation in SHOW and I_S.  Please admit that this is a bug and an
> oversight from MariaDB to forget about this!

Agree, these could be useful.

On the other hand, virtual columns were implemented in MariaDB-5.2, in 2010.
And in these almost five years nobody ever requested these features for
SHOW and I_S, as far as I remember.

So, I don't believe I can be a judge of what is useful and what is not,
I got it wrong oh so many times.

Do you need these SHOW/I_S extensions? Please, create an issue in Jira
for them, if you do.

Regards,
Sergei

> Field    Type     Null    Key
> 
> 
> select version(); -- 5.7.5-labs-preview
> 
> create table comments(
>   userid int AS (ExtractValue(comment,'/comment/userid')) STORED,
>   comment TEXT,
>   KEY(userid));
> 
> 
> show columns from comments;
> /*Default  Extra
> -------  -------  ------  ------  -------  ---------
> userid   int(11)  YES     MUL     (NULL)   VIRTUAL
> comment  text     YES             (NULL)
> */
> 
> describe comments;
> /*
> Field    Type     Null    Key     Default  Extra
> -------  -------  ------  ------  -------  ---------
> userid   int(11)  YES     MUL     (NULL)   VIRTUAL
> comment  text     YES             (NULL)
> */
> 
> show full fields from comments;
> /*
> Field    Type     Collation          Null    Key     Default  Extra
>  Privileges                       Comment
> -------  -------  -----------------  ------  ------  -------  -------
>  -------------------------------  ---------
> userid   int(11)  (NULL)             YES     MUL     (NULL)   VIRTUAL
>  select,insert,update,references
> comment  text     latin1_swedish_ci  YES             (NULL)
>  select,insert,update,references
> */
> 
> select * from information_schema.`COLUMNS` where TABLE_NAME = 'comments';
> 
> /*
> TABLE_CATALOG  TABLE_SCHEMA  TABLE_NAME  COLUMN_NAME  ORDINAL_POSITION
>  COLUMN_DEFAULT  IS_NULLABLE  DATA_TYPE  CHARACTER_MAXIMUM_LENGTH
>  CHARACTER_OCTET_LENGTH  NUMERIC_PRECISION  NUMERIC_SCALE
>  DATETIME_PRECISION  CHARACTER_SET_NAME  COLLATION_NAME     COLUMN_TYPE
>  COLUMN_KEY  EXTRA    PRIVILEGES                       COLUMN_COMMENT
>  GENERATION_EXPRESSION
> -------------  ------------  ----------  -----------  ----------------
>  --------------  -----------  ---------  ------------------------
>  ----------------------  -----------------  -------------
>  ------------------  ------------------  -----------------  -----------
>  ----------  -------  -------------------------------  --------------
>  -----------------------------------------
> def            test          comments    userid                      1
>  (NULL)          YES          int                          (NULL)
>        (NULL)                 10              0              (NULL)  (NULL)
>              (NULL)             int(11)      MUL         VIRTUAL
>  select,insert,update,references
>  ExtractValue(comment,'/comment/userid')
> def            test          comments    comment                     2
>  (NULL)          YES          text                          65535
>         65535             (NULL)         (NULL)              (NULL)  latin1
>              latin1_swedish_ci  text
>  select,insert,update,references
> 
> */