Transaction Questions

Hi,

Following on from my last question, I'm attempting to write a function that inserts periods. Periods are either bookings, available, or unavailable, each stored in a seperate table, and all have start date and end date columns, all of which inherit a table 'calendar_entries'.

The function needs to check that there are no overlapping periods, so I need to check all three tables - I need to prevent entries being added in parrell for the duration of the function. My question is - Is it sufficient to LOCK calendar_entries IN EXCLUSIVE MODE, or do I need to lock all three tables individually?

Also, inside the function I need to use a transaction in order to DELETE one row, and UPDATE another. Will this 'inner' transaction have write access to all 3 tables?

Just trying to get my head around concurrency - Have a good weekend!

Ta,

Neil.

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