Re: The same prepared query yield "-1" the first six times and then "-1.0"

On Tue, 22 Aug 2023 at 01:54, Edoardo Panfili <edoardopa(at)gmail(dot)com> wrote:

>
>
> Il giorno 21 ago 2023, alle ore 21:37, Dave Cramer
> <davecramer(at)postgres(dot)rocks> ha scritto:
>
>
>
> On Mon, 21 Aug 2023 at 14:42, Edoardo Panfili <edoardopa(at)gmail(dot)com> wrote:
>
>>
>>
>> > Il giorno 21 ago 2023, alle ore 20:13, Peter J. Holzer <
>> hjp-pgsql(at)hjp(dot)at> ha scritto:
>> >
>> > On 2023-08-21 17:27:20 +0200, Edoardo Panfili wrote:
>> >> The attended result was a sequence of ten equal values but this is the
>> actual result:
>> >> p: -1
>> >> p: -1
>> >> p: -1
>> >> p: -1
>> >> p: -1
>> >> p: -1.0
>> >> p: -1.0
>> >> p: -1.0
>> >> p: -1.0
>> >> p: -1.0
>> > [...]
>> >> 2023-08-21 11:51:50.633 CEST [1511] user(at)testdb LOG: execute
>> <unnamed>: SET extra_float_digits = 3
>> >> 2023-08-21 11:51:50.634 CEST [1511] user(at)testdb LOG: execute
>> <unnamed>: SET application_name = 'PostgreSQL JDBC Driver'
>> >> 2023-08-21 11:51:50.644 CEST [1511] user(at)testdb LOG: execute
>> <unnamed>: SELECT dim1 FROM number WHERE name='first'
>> >> 2023-08-21 11:51:50.648 CEST [1511] user(at)testdb LOG: execute
>> <unnamed>: SELECT dim1 FROM number WHERE name='first'
>> >> 2023-08-21 11:51:50.649 CEST [1511] user(at)testdb LOG: execute
>> <unnamed>: SELECT dim1 FROM number WHERE name='first'
>> >> 2023-08-21 11:51:50.650 CEST [1511] user(at)testdb LOG: execute
>> <unnamed>: SELECT dim1 FROM number WHERE name='first'
>> >> 2023-08-21 11:51:50.651 CEST [1511] user(at)testdb LOG: execute S_1:
>> SELECT dim1 FROM number WHERE name='first'
>> >> 2023-08-21 11:51:50.651 CEST [1511] user(at)testdb LOG: execute S_1:
>> SELECT dim1 FROM number WHERE name='first'
>> >> 2023-08-21 11:51:50.653 CEST [1511] user(at)testdb LOG: execute S_1:
>> SELECT dim1 FROM number WHERE name='first'
>> >> 2023-08-21 11:51:50.653 CEST [1511] user(at)testdb LOG: execute S_1:
>> SELECT dim1 FROM number WHERE name='first'
>> >> 2023-08-21 11:51:50.654 CEST [1511] user(at)testdb LOG: execute S_1:
>> SELECT dim1 FROM number WHERE name='first'
>> >> 2023-08-21 11:51:50.656 CEST [1511] user(at)testdb LOG: execute S_1:
>> SELECT dim1 FROM number WHERE name=‘first'
>> >
>> > Are these outputs from the same run?
>> Yes
>>
>> >
>> > I notice that the output from the program switches after 5 queries from
>> > "-1" to "-1-0", but the logged query name switches after 4 queries from
>> > "<unnamed>" to "S_1”.
>>
>> You’re right. It seem a JDBC side problem. I am doing some tests using
>> suggestions from pgsql-jdbc list.
>>
>> What sounds strange to me is that switching from “mode_X” to “mode_Y” I
>> obtain different representation of the same value,
>>
>> I know the value is semantically the same.. but… in some way I like to
>> see.. "a perfect postgresql env” (as it absolutely is)
>>
>> Edoardo
>>
>>
> I have confirmed that this behaviour is by design either by postgres or
> the driver. When postgres provides us the data using text mode we see -1
>
> (psql)
> select * from number ;
> name | dim1
> -------+------
> first | -1
>
> This is the way the data is presented by the text output function.
>
> And I expected to obtain the same from the JDBC connection
>
>
> In binary mode we see -1.0. This is an artifact of the binary output
> function.
>
> If ResultSet.getDouble is used the data is the same ... -1 for both text
> and binary
>
> Using getString we see the problem.
>
> So you have a few options to stop this: Set prepareThreshold to 0 and the
> driver will not switch to named statements or binary,
>
> Properties props = new Properties();
> props.setProperty("prepareThreshold", "0");
> Connection conn = DriverManager.getConnection(
> "jdbc:postgresql://192.168.64.7:5432/testdb?user=user&password=password”,
> props);
>
> Obtains “-1” all the times
>

You do give up the advantage of named statements which is that DESCRIBE
won't be necessary, but that does appear to be less of a problem than
returning a different representation.

Dave