I'm doing some tests, but have a questions about locking.

In a innodb table, if you issue an select for update lock for a row,
supposedly, it only locks that row, but if you don't issue a select for
update, and trow the update... does it locks the hole table?

The update goes over an indexed field, or the effect of locking the hole
table is due I'm updating an indexed field?

This is because I'm running into dead locks, but I know there is no select
for update to the row being updated.


Thanks.