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Re: Prepare Statement

From: "Jie Liang" <jie(at)stbernard(dot)com>
To: "Kris Jurka" <books(at)ejurka(dot)com>
Cc: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, <pgsql-sql(at)postgresql(dot)org>,<pgsql-jdbc(at)postgresql(dot)org>
Subject: Re: Prepare Statement
Date: 2004-06-17 22:50:33
Message-ID: E7E213858379814A9AE48CA6754F5ECB03451936@mail01.stbernard.com (view raw or flat)
Thread:
Lists: pgsql-jdbcpgsql-sql
Hmm, intersting.
I am using jdk 1.3.1, and pg74.213.jdbc2.jar driver, I hope this bug
could be fixed in later version.

Thanks.



Jie Liang

-----Original Message-----
From: Kris Jurka [mailto:books(at)ejurka(dot)com] 
Sent: Thursday, June 17, 2004 3:26 PM
To: Jie Liang
Cc: Tom Lane; pgsql-sql(at)postgresql(dot)org; pgsql-jdbc(at)postgresql(dot)org
Subject: Re: [JDBC] Prepare Statement




On Thu, 17 Jun 2004, Jie Liang wrote:

> Kris,
> You are right, I modified that piece of code a little bit, 
> CallableStatement stmt = conn.prepareCall("{?=call chr(?)}"); Then my 
> log file were: Select * from chr(65) as result;
> Select * from chr(66) as result;
> ......
> However, if I use:
> PrepareStatement stmt = conn.prepareStatement("SELECT chr(?)");
> Then my log file are same as yours.i.e. it use PREPARE and EXECUTE.
> 
> So, I am getting confusion.
> I think CallableStatement is extended from PrepareStatement, it should

> have same behaviou.
> 

What's happening here is that you can only use prepared statements for 
certain operations.  You can't for example prepare a CREATE TABLE 
statement.  The driver examines the query to see if it is valid for 
preparing and I believe the problem here is that with a callable
statement 
it is examinging the query with "call" before it is transformed to a 
SELECT, so it doesn't recognize it as a preparable.  This looks like a
bug 
to me.

Kris Jurka


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