MySQL Forums :: Transactions :: Problem: A SELECT ... FOR UPDATE statement locking all rows in a table

MySQL Server version 5.1.41 with InnoDB plugin enabled. I have the following three tables for invoices: invoices, invoice_components and invoice_expenses. Table invoices has invoice_id primary key. Both invoice_components and invoice_expenses are linked to table invoices with invoice_id as a non-unique foreign_key (each invoice can have more than one component and more than one expense). Both tables have a BTREE index for this foreign key.

I have the following transactions:

transaction 1:
START TRANSACTION;
SELECT * FROM invoices WHERE invoice_id = 18 FOR UPDATE;
SELECT * FROM invoice_components WHERE invoice = 18 FOR UPDATE;
SELECT * FROM invoice_expenses WHERE invoice = 18 FOR UPDATE;

EVerything works ok for the first transaction and the rows are selected and locked.

transaction 2:
START TRANSACTION;
SELECT * FROM invoices WHERE invoice_id = 19 FOR UPDATE;
SELECT * FROM invoices WHERE invoice = 19 FOR UPDATE;
SELECT * FROM invoice_expenses WHERE invoice = 19 FOR UPDATE;

The second transaction returns "ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction" for the third query.

The same happens when I try to SELECT ... FOR UPDATE other invoices and their components and expenses. It seems the first transaction has locked all the rows in invoice_expenses table. Any ideas why this is happening?