Improve device mgt core performance #394

When device count is exceeding more than 300,000 DM_DEVICE table and DM_ENROLMENT table related queries are taking more than 30s to execute. In order to resolve this downgraded DB normalization level to 2 from 3 and added DEVICE_TYPE and DEVICE_IDENTIFICATION columns to DM_ENROLMENT table, in order to minimize the requirement of joining DM_DEVICE table always for DM_ENROLMENT related queries.

Data migration:

ALTER TABLE `DM_ENROLMENT`
ADD COLUMN `DEVICE_TYPE` VARCHAR(300) NOT NULL AFTER `DEVICE_ID`,
ADD COLUMN `DEVICE_IDENTIFICATION` VARCHAR(300) NOT NULL AFTER `DEVICE_TYPE`,
DROP INDEX `IDX_ENROLMENT_DEVICE_ID_TENANT_ID`,
DROP INDEX `IDX_ENROLMENT_DEVICE_ID_TENANT_ID_STATUS`;

CREATE INDEX IDX_ENROLMENT_DATE_OF_LAST_UPDATE ON DM_ENROLMENT(DATE_OF_LAST_UPDATE);
CREATE INDEX IDX_ENROLMENT_DEVICE_IDENTIFICATION ON DM_ENROLMENT(DEVICE_IDENTIFICATION);
CREATE INDEX IDX_ENROLMENT_DEVICE_TYPE ON DM_ENROLMENT(DEVICE_TYPE);
CREATE INDEX IDX_ENROLMENT_STATUS ON DM_ENROLMENT(STATUS);
CREATE INDEX IDX_ENROLMENT_TENANT_ID ON DM_ENROLMENT(TENANT_ID);

UPDATE `DM_ENROLMENT` e
	JOIN `DM_DEVICE` d ON e.DEVICE_ID = d.ID
	JOIN `DM_DEVICE_TYPE` dt ON dt.ID = d.DEVICE_TYPE_ID
SET
e.DEVICE_TYPE = dt.NAME,
e.DEVICE_IDENTIFICATION = d.DEVICE_IDENTIFICATION;


CREATE INDEX IDX_DM_DEVICE_DEVICE_IDENTIFICATION ON DM_DEVICE(DEVICE_IDENTIFICATION);
CREATE INDEX IDX_DM_DEVICE_LAST_UPDATED_TIMESTAMP ON DM_DEVICE(LAST_UPDATED_TIMESTAMP);