MySQL compatibility: TO_DAYS function

[slvrtrn]

This one is a minor one but is still used by Tableau online when converting DateTime columns during the table column types introspection stage.

Sample generated query:

SELECT `cell_towers`.`area`                        AS `area`,
       `cell_towers`.`averageSignal`               AS `averageSignal`,
       `cell_towers`.`cell`                        AS `cell`,
       `cell_towers`.`changeable`                  AS `changeable`,
       `cell_towers`.`created`                     AS `created`,
       `cell_towers`.`lat`                         AS `lat`,
       `cell_towers`.`lon`                         AS `lon`,
       `cell_towers`.`mcc`                         AS `mcc`,
       `cell_towers`.`net`                         AS `net`,
       `cell_towers`.`radio`                       AS `radio`,
       `cell_towers`.`range`                       AS `range`,
       `cell_towers`.`samples`                     AS `samples`,
       `cell_towers`.`unit`                        AS `unit`,
       (TO_DAYS(`cell_towers`.`updated`) - 693961) AS `updated`
FROM `cell_towers`
LIMIT 100

which fails, because

Code: 46. DB::Exception: Unknown function TO_DAYS

How to reproduce

• Which ClickHouse server version to use: latest master
• Which interface to use, if matters: MySQL
• Sample data for all these tables: cell_towers sample dataset

Expected behavior

TO_DAYS function works like in MySQL