Re: JDBC Transactions

On 01/11/10 18:08, Andy Colson wrote:
> 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

Hi Andy,

Thanks for your reply. Would the above code be classed as a single
transaction then? And if so, I could just simple leave out the line
which says "//Insert SQL here to lock table"?

Thanks