I think you're missing the concept of a transaction in the database sense. The idea behind a transaction is that you can perform multiple steps and if you don't complete all steps, any changes are reversed. The reversal process is handled by the database. A good example is moving money from bank account A to B. You specify how much to move and that amount is debited from account A and credited to account B, 2 steps. If the first step happens, but not the second, then the first step needs to be reversed. Until the transaction is complete, anything querying the data needs to see bank account in it's state before any transaction started, a type of versioning. You seem to be trying implement all this manually, which you would need to do if you are using MyISAM based tables. But you may not need to use transactions at all if your data does not have real time dependencies.
On 6/4/07, David T. Ashley <[EMAIL PROTECTED]> wrote:
I decided to go with a simple paradigm for my web-based database. Rather than transactions, each process locks the entire database while it is changing something, then unlocks it. This just serializes access (all other processes will block until the one modifying the database has finished). The method I was using is something like: LOCK TABLE thistable, thattable, theothertable, goshthislistcangetlongtable; Do whatever is needed; UNLOCK TABLES; I probably botched the syntax above. Rather than enumerate every table in the database (which could get to be a long list), I wondered if it is possible to just lock one table, with the gentleman's agreement that in order to modify the database, every process must first lock that particular table. For example: #1)LOCK TABLE x; #2)Make modifications to tables x, y, and z; #3)UNLOCK TABLES; Are there any race conditions in just using one table for this purpose? For example, SQL guarantees that a given SQL statement is atomic. But it is guaranteed that #2 will complete before #3 above? If every process uses the same rule, can anything unexpected happen? One more note: I'm sure that many of the skilled users on this list will be tempted to advocate more sophisticated methods. I appreciate all advice, but I'm just looking for an easy way to serialize access to my database and guarantee mutual exclusion. Each operation I want to do would take at most half a second, so another web process waiting that long won't make a difference. Simpler is easier for me. Thanks.
