Perform one-time migration of Test, Stage, Prod database for file modification time

[kburke]

Execute the SQL commands below to migrate existing databases for uuid-api #115, rather than dump and reload each database.

-- Add the new column in the DDL modifications for https://github.com/hubmapconsortium/uuid-api/issues/115
ALTER TABLE `hm_uuid`.`files`
ADD `LAST_MODIFIED` timestamp NOT NULL DEFAULT now() ON UPDATE now()
;

-- Change column to align with the DDL modifications for https://github.com/hubmapconsortium/uuid-api/issues/115
ALTER TABLE `hm_uuid`.`uuids` 
ALTER  `TIME_GENERATED` SET DEFAULT (now())
;

-- Revise column values set during ALTER statement above to a reasonable value pulled from UUID.TIME_GENERATED.
-- 2,989,892 rows in 98 seconds on Dev
-- 2,989,805 rows in 98 seconds on Test
-- 2,991,145 rows in 98 seconds on Prod
UPDATE `hm_uuid`.`files`
SET
`LAST_MODIFIED` = (SELECT `TIME_GENERATED` FROM `hm_uuid`.`uuids` where `uuids`.`UUID`=`files`.`UUID`)
;

-- verify times on two tables are the same after UPDATE
SELECT u.TIME_GENERATED, f.LAST_MODIFIED
FROM `hm_uuid`.`uuids` AS u
	INNER JOIN `hm_uuid`.`files` AS f ON u.`UUID`=f.`UUID`
WHERE u.`TIME_GENERATED` <> f.`LAST_MODIFIED`
;

-- verify no other outliers
SELECT *
FROM `hm_uuid`.`files` AS f
WHERE f.`LAST_MODIFIED` IS NULL OR f.`LAST_MODIFIED` > now() OR f.`LAST_MODIFIED` < (SELECT min(time_generated) FROM hm_uuid.uuids);

[kburke]

UPDATE command results.
-- 2,989,892 rows in 98 seconds on Dev
-- 2,989,805 rows in 98 seconds on Test

Stage still not running it's own uuid-api.

Will backup PROD and take offline for update around lunchtime.

[kburke]

UPDATE command results while in maintenance mode, announced on #hive-developers Slack channel:
-- 2,991,145 rows in 98 seconds on Prod