Updating a System Versioned Table always causes a row to be updated, regardless if the data is the same or not

Good Morning,

If you run an update on a non-system versioned table, and the column(s) you update contain the same data, then no rows are updated. However, if you add system versioning to a table, then an update will always update the rows selected by the WHERE clause; regardless of if the values were updated or not.

This has the side effect of unnecessarily increasing the size of the history, as a new history row is created, despite there being no change. I am not certain if this is intended behaviour or not, so I believe as a minimum this should be documented (as SV tables behave differently to normal tables) - however ideally this would be changed, or a configuration option added to control if an no change UPDATE causes a new history row or not.

Test Script

/* Setup */

CREATE TABLE `bugTest`.`nsvTable` (

  `i` INT UNSIGNED NOT NULL,

  PRIMARY KEY (`i`)

) ENGINE = INNODB;

INSERT INTO `nsvTable` (`i`) VALUES(1);

CREATE TABLE `bugTest`.`svTable` (

  `i` INT UNSIGNED NOT NULL,

  PRIMARY KEY (`i`)

) ENGINE = INNODB WITH SYSTEM VERSIONING;

INSERT INTO `svTable` (`i`) VALUES(1);

/* Test Updates */

UPDATE `nsvTable` SET `i` = 1 WHERE `i` = 1;

/* 0 row(s) affected */

UPDATE `svTable` SET `i` = 1 WHERE `i` = 1;

/* 1 row(s) affected */

/* Cleanup */

DROP TABLE `nsvTable`, `svTable`;