Question

I am making a webservice in PHP which does a series of calculations based on a select from a table and then updates the table afterwards with the new results.

However i want to prevent the case where another person is making a call to the same webservice while another person’s session is still doing an update.

Is it the right thing here to lock that entire table and then unlock it again? If so, how do i lock and unlock a mysql table using PHP pdo?

Answer 1

I posted a comment:

Not a direct answer, but I don’t think this is any problem. The
calculations and fetching data from the database is done within a few
milliseconds. The chances or two people interacting at the same time
is soooo small that most people don’t bother making a lock like this.

But if these calculations are critical you could prevent this problem by adding a new field and simply call it occupied, busy or something like that.

When you run your script, check if this field is set to for example 1, if it is, make the script sleep for 1-2-3 seconds and then retry. If this field is set to 0, update it to 1, do the calculations and set it back to 0 again.

This would prevent two people from accessing the same values at the same time.