On 11/1/2010 12:37 PM, Jonathan Tripathy wrote:
> Hi Everyone,
>
> I'm trying to create a server for a database system which will be used
> by multiple clients. Of course, table locking is very important. Reading
> the Postgresql docs, locking occurs on a transaction-by-transaction basis.
>
> In our java code, we are doing this:
>
> //Start Code Block
>
> Connection con = "..."
> con.setAutoComitt(false);
>
> //Insert SQL here to lock table
>
> String qry1 = "..."
> pst1 = con.prepareStatement(qry1)
> //Insert code here to add values to prepared statement pst1
> pst1.executequery();
>
> String qry2 = "..."
> pst2 = con.prepareStatement(qry2)
> //Insert code here to add values to prepared statement pst2
> pst2.executequery();
>
> con.comitt();
>
> //End Code Block
>
> My question is, would the above block of code be classed as a single
> transaction, and would the locking work correctly?
>
> Thanks
>
> Jonny
>
>
Table locking is very bad for concurrent access. When a table is
locked, its one user at a time.
PG usually does not need any locks at all. As long as you use
transactions as they were meant to be used (as an atomic operation),
things usually work really well, with no locking at all. You could read
up on MVCC is you were interested.
Without knowing what sql you are running, I can _totally guarantee_
it'll work perfectly with NO table locking. :-)
-Andy