Is it necessary to rollback if commit fails?

问题

This seems like a simple enough question, yet I couldn't find any definitive answers specific for MySQL. Look at this:

$mysqli->autocommit(false); //Start the transaction
$success = true;    

/* do a bunch of inserts here, which will be rolled back and
   set $success to false if they fail */

if ($success) {
    if ($mysqli->commit()) {
        /* display success message, possibly redirect to another page */
    }
    else {
        /* display error message */
        $mysqli->rollback(); //<----------- Do I need this?
    }
}

$mysqli->autocommit(true); //Turns autocommit back on (will be turned off again if needed)

//Keep running regardless, possibly executing more inserts

The thing is, most examples I have seen just end the script if commiting failed, either by letting it finish or by explicitly calling exit(), which apparently auto rolls back the transaction(?), but what if I need to keep running and possibly execute more database-altering operations later? If this commit failed and I didn't have that rollback there, would turning autocommit back on (which according to this comment on the PHP manual's entry on autocommit does commit pending operations) or even explicitly calling another $mysqli->commit() later on, attempt to commit the previous inserts again, since it failed before and they weren't rolled back?

I hope I've been clear enough and that I can get a definitive answer for this, which has been bugging me quite a lot.

Edit: OK, maybe I phrased my question wrong in that line comment. It's not really a matter of whether or not I need the rollback, which, as it was pointed out, would depend on my use case, but really what is the effect of having or not having a rollback in that line. Perhaps a simpler question would be: does a failed commit call discards pending operations or does it just leaves them in their pending state, waiting for a rollback or another commit?

来源：https://stackoverflow.com/questions/38133260/is-it-necessary-to-rollback-if-commit-fails

标签

php

mysql

commit

rollback