MDEV-10825 Feature Request: Persist exact view definitions DDL10.6-mdev-10825

MDEV-13805 SHOW CREATE VIEW don't provide formating in .frm file

This patch extends I_S.views with an extra column called SOURCE.
"SOURCE" is a verbatim copy of the view's frm field source=...

TODO
A few feature details need to be ironed out:
* Should we make sure that SOURCE is a verbatim copy of create view?
  Currently we only present the select statement.

https://database.guide/4-ways-to-get-a-view-definition-using-transact-sql/

SQL Server for the "definition" column has the following:

SELECT definition
FROM sys.sql_modules
WHERE object_id = object_id('Website.Customers');

+--------------+
| definition   |
|--------------|
|
CREATE VIEW Website.Customers
AS
SELECT s.CustomerID,
       s.CustomerName,
       sc.CustomerCategoryName,
       pp.FullName AS PrimaryContact,
       ap.FullName AS AlternateContact,
       s.PhoneNumber,
       s.FaxNumber,
       bg.BuyingGroupName,
       s.WebsiteURL,
       dm.DeliveryMethodName AS DeliveryMethod,
       c.CityName AS CityName,
       s.DeliveryLocation AS DeliveryLocation,
       s.DeliveryRun,
       s.RunPosition
FROM Sales.Customers AS s
LEFT OUTER JOIN Sales.CustomerCategories AS sc
ON s.CustomerCategoryID = sc.CustomerCategoryID
LEFT OUTER JOIN [Application].People AS pp
ON s.PrimaryContactPersonID = pp.PersonID
LEFT OUTER JOIN [Application].People AS ap
ON s.AlternateContactPersonID = ap.PersonID
LEFT OUTER JOIN Sales.BuyingGroups AS bg
ON s.BuyingGroupID = bg.BuyingGroupID
LEFT OUTER JOIN [Application].DeliveryMethods AS dm
ON s.DeliveryMethodID = dm.DeliveryMethodID
LEFT OUTER JOIN [Application].Cities AS c
ON s.DeliveryCityID = c.CityID
              |
+--------------+
(1 row affected)

1 files changed, 5 insertions, 0 deletions

diff --git a/sql/sql_show.cc b/sql/sql_show.cc
index b1cc696e9fe..b4d91b050bc 100644
--- a/sql/sql_show.cc
+++ b/sql/sql_show.cc
@@ -6867,6 +6867,10 @@ static int get_schema_views_record(THD *thd, TABLE_LIST *tables,
 
     table->field[10]->store(view_algorithm(tables), cs);
 
+    if (tables->allowed_show)
+      table->field[11]->store(tables->source.str, tables->source.length,
+                              tables->view_creation_ctx->get_client_cs());
+
     if (schema_table_store_record(thd, table))
       DBUG_RETURN(1);
     if (unlikely(res && thd->is_error()))
@@ -9125,6 +9129,7 @@ ST_FIELD_INFO view_fields_info[]=
   Column("CHARACTER_SET_CLIENT", CSName(),   NOT_NULL, OPEN_FRM_ONLY),
   Column("COLLATION_CONNECTION", CSName(),   NOT_NULL, OPEN_FRM_ONLY),
   Column("ALGORITHM",            Varchar(10),NOT_NULL, OPEN_FRM_ONLY),
+  Column("SOURCE",          Longtext(65535), NOT_NULL, OPEN_FRM_ONLY),
   CEnd()
 };