Hi Anel!

I've reviewed your patch and generally things look good. You do some good analysis usually and I think we should highlight your work to the broader developer scene. I've thus CC'ed this email to the maria-developers mailing list. This gives us a chance to get feedback from outside, particularly as this feature is of general interest to the community.

Please include the .result files in future versions as it makes reviewing a lot easier.

Serg: coding style and implementation aside, I'll do the review on that bit, please have a look at Anel's patch and suggest if you think the current table header for I_S.check_constraints is good enough for our needs or if you have more input on this task.

Relevant bit:

+ST_FIELD_INFO check_constraints_fields_info[]=
+{
+  {"CONSTRAINT_CATALOG", FN_REFLEN, MYSQL_TYPE_STRING, 0, 0, 0, OPEN_FULL_TABLE},
+  {"CONSTRAINT_SCHEMA", NAME_CHAR_LEN, MYSQL_TYPE_STRING, 0, 0, 0,
+   OPEN_FULL_TABLE},
+  {"CONSTRAINT_NAME", NAME_CHAR_LEN, MYSQL_TYPE_STRING, 0, 0, 0,
+   OPEN_FULL_TABLE},
+  {"TABLE_SCHEMA", NAME_CHAR_LEN, MYSQL_TYPE_STRING, 0, 0, 0, OPEN_FULL_TABLE},
+  {"TABLE_NAME", NAME_CHAR_LEN, MYSQL_TYPE_STRING, 0, 0, 0, OPEN_FULL_TABLE},
+  {"CHECK_CLAUSE", NAME_CHAR_LEN, MYSQL_TYPE_STRING, 0, 0, 0,
+   OPEN_FULL_TABLE},
+  {0, 0, MYSQL_TYPE_STRING, 0, 0, 0, SKIP_OPEN_TABLE}
+};

Vicențiu
 
On Thu, 29 Mar 2018 at 12:01 Anel Husakovic <anel@mariadb.org> wrote:
Hi Vin,

I'm pleased to announce my new patch prototype for MDEV 14474 where are implemented field and table constraints: 

According to the standard there are only 4 column to represent.
CONSTRAINT_CATALOG, CONSTRAINT_SCHEMA, CONSTRAINT_NAME,CHECK_CLAUSE
But because Serg mentioned that alternative would be to change information_schema.table_constraints with adding only 1 column (check_clause) I also used 2 additional columns which are represented also in table_constraints and they are TABLE_SHEMA , TABLE_NAME.
 
Function of interest is: get_check_constraints_record

Also I added 2 test cases:

One that works with only 1 table:  MDEV14474-one_table_play.test
Second that works with more tables:  MDEV14474-I_S_check_constraint.test

Last night I had a problem with field constraints. 
As a reference I used only way how currently all check constraints are shown and its obtained via show create table t;

Bellow is shown that  field constraints were not visible as well as that name used for them is NULL, at least this is how show create table represented them ( there is no way to give a name to a field constraint for example: f int constraint name check(f<0)). According to my opinion, because this constraint belongs to the field, it should be also called as a name of a field and not NULL.
As an argument to my opinion here is mariadb  kb  https://mariadb.com/kb/en/library/constraint/
Please take a look at constraint name, which is field constraint and error message.
INSERT INTO t2(name, start_date, end_date) VALUES('Io', '2003-12-15', '2014-11-09');
ERROR 4022 (23000): CONSTRAINT `name` failed for `test`.`t2`
If the name of constraint = name of the field , than definitely it is not consistent with show create table output, and show create table output needs to be changed,  , but this is question that I would like to discuss with you ?!  

When you try to use show create table x
image.png


I'm waiting on your reply for global temporary tables as well as check_constraints and how to proceed further 

Not understand yet a concept:

In sql/table.h
There is a struct st_schema_table which has fill data and process data.

How they work, and how to use that on other database for example PSI.

Regards,

Anel