Question

What happens if I commit a pdo transaction where one or more entries are duplicates of already existing primary keys? Will the transaction insert all of the none duplicates or roll back?

If it is the latter, how can I prevent the rollback?

Answer 1

You won’t be able to commit such transaction, because you won’t be able to insert such rows in the first place.

See below
In MySQL console #1 we do this:

mysql> USE TEST;
Database changed
mysql> CREATE TABLE trTest(ID INT UNSIGNED PRIMARY KEY) ENGINE = InnoDB;
Query OK, 0 rows affected (0.46 sec)

mysql> START TRANSACTION;
Query OK, 0 rows affected (0.00 sec)

mysql> INSERT INTO trTest VALUES (1);
Query OK, 1 row affected (0.00 sec)

Then in console #2 we try:

mysql> USE TEST;
Database changed
mysql> START TRANSACTION;

Query OK, 0 rows affected (0.00 sec)
mysql> INSERT INTO trTest VALUES (1);

The prompt will not return here and the session will hang for a while until…

ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction