Thread: ResultSet problem in JDBC

ResultSet problem in JDBC

From

Zhipan Wang

Date:

02 December 2010, 04:14:58

p { margin: 0; }

Hi all,
I am writing a Java program using postgres. When I run my program, I got the following error message:

Exception in thread "main" org.postgresql.util.PSQLException: Can't infer the SQL type to use for
an instance of org.postgresql.jdbc4.Jdbc4ResultSet. Use setObject() with an explicit Types value to specify the type to use.
    at org.postgresql.jdbc2.AbstractJdbc2Statement.setObject(AbstractJdbc2Statement.java:1772)
    at org.postgresql.jdbc3g.AbstractJdbc3gStatement.setObject(AbstractJdbc3gStatement.java:37)
    at org.postgresql.jdbc4.AbstractJdbc4Statement.setObject(AbstractJdbc4Statement.java:46)
    at Cracking.testMethod(Cracking.java:619)
    at GetConnection.main(GetConnection.java:97)

My code that caused this problem is:

Statement st = c.createStatement();
ResultSet r = st.executeQuery("select unnest(col0) from relation2_col1 where keyValue<500");
PreparedStatement sql = c.prepareStatement( "SELECT col1 FROM relation2 WHERE col0 IN ?");
sql.setObject(1, r);
ResultSet result = sql.executeQuery();

I am using Eclipse, and there is no warning for this code.
Can't a result set be used in another query? How do I correct it?

Re: ResultSet problem in JDBC

From

Craig Ringer

Date:

02 December 2010, 05:44:46

On 02/12/10 13:14, Zhipan Wang wrote:

> Statement st = c.createStatement();
> ResultSet r = st.executeQuery("select unnest(col0) from relation2_col1
> where keyValue<500");
> PreparedStatement sql = c.prepareStatement( "SELECT col1 FROM relation2
> WHERE col0 IN ?");
> sql.setObject(1, r);
> ResultSet result = sql.executeQuery();

You appear to be trying to implement a subquery client-side. Why not
just use:

PreparedStatement sql = c.prepareStatement(
          "SELECT col1 FROM relation2 WHERE col0 IN "+
          "(SELECT unnest(col0) from relation2_col1 where keyValue<500"
          );

? It's hard to know whether the above is correct because you've failed
to provide your schema, but something along those lines seems to fit
your intent from the code above.

> I am using Eclipse, and there is no warning for this code.

No, Eclipse can't know the details of how every JDBC driver works.

> Can't a result set be used in another query? How do I correct it?

Either build an array with the contents of the resultset and pass that,
or avoid the weirdness by using a subquery directly.

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