Hello:
I have one question about prepared statement.
I use Java via JDBC, then send prepared statement to execute.
I thought that the pg_prepared_statments view will have one record after my execution.
But I can't find.
Is the JDBC's prepared statement differ from SQL execute by prepare command ?
http://www.postgresql.org/docs/current/static/sql-prepare.html
My simple java program is the following:
import java.sql.*;
public class Test01 {
public static void main(String argsv[]){
try
{
Class.forName("org.postgresql.Driver").newInstance();
String url = "" ;
Connection con = DriverManager.getConnection(url,"postgres","postgres" );
///Phase 1:-------------Select data from table-----------------------
System.out.println("Phase 1------------------------start");
String strsql = " select * from customers where cust_id = ?";
PreparedStatement pst=con.prepareStatement(strsql);
pst.setInt(1,3); //find the customer with cust_id of 3.
ResultSet rs = pst.executeQuery();
while (rs.next())
{
System.out.print("cust_id:"+rs.getInt( "cust_id"));
System.out.println("...cust_name:"+rs.getString( "cust_name" ));
}
System.out.println("Phase 1------------------------end\n");
///Phase 2:-------------Use connection again,to select data from data dictionary-----------------------
System.out.println("Phase 2------------------------start");
strsql = "select * from pg_prepared_statements";
pst=con.prepareStatement(strsql);
rs = pst.executeQuery();
while (rs.next())
{
System.out.println("statement:"+rs.getString( "statement"));
}
System.out.println("Phase 2------------------------end\n");
///Phase 3:-------------Use connection again,to select data from table-----------------------
System.out.println("Phase 3------------------------start");
strsql = "select * from customers";
pst=con.prepareStatement(strsql);
rs = pst.executeQuery();
while (rs.next())
{
System.out.print("cust_id:"+rs.getInt( "cust_id"));
System.out.println("...cust_name:"+rs.getString( "cust_name" ));
}
System.out.println("Phase 3------------------------end\n");
rs.close();
pst.close();
con.close();
}
catch (Exception ee)
{
System.out.print(ee.getMessage());
}
}
}
The result of it's execution is:
Phase 1------------------------start
cust_id:3...cust_name:Taylor
Phase 1------------------------end
Phase 2------------------------start
Phase 2------------------------end
Phase 3------------------------start
cust_id:1...cust_name:Smith
cust_id:2...cust_name:Brown
cust_id:3...cust_name:Taylor
Phase 3------------------------end
That is to say: my prepared statement is not cached by PG?
Then how to write a java program to made it's prepared statement realized by PG to treat it as a "prepared statement"?
Thank you.
