Re: LOCKing method in my situation?

Alexander Popkov wrote:
> Hello PostgreSQL gurus!
>
> I am have question to you.
>
> I am have table 'chall_item' in my database.
> In many PHP scripts i am do 'SELECT * FROM chall_item....', but
> in one script (join.php) i do
>   a) SELECT COUNT(*) FROM chall_item WHERE chall_no = XXX;
>   b) if returned number less then 10, then i do INSERT INTO chall_item (chall_no, ...) VALUES (XXX, ...);
>
> But if beetwen a) and b) other instance of 'join.php' do part "a)" - then odd row are added ;(
>
> I can do LOCK TABLE chall_item IN ACCESS EXCLUSIVE MODE,
> but IMHO this is not true method in this situation, because i need lock only for 'join.php'
> not for all scripts. Help me plz. Which other methods are exist in this situation.
>



If I understand you question correctly you have to use a SERIALIZABLE
transaction to make sure that you can see the same snapshot during your
transaction.

    Regards,

        Hans


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