On Mon, 21 Aug 2023 at 14:42, Edoardo Panfili <edoardopa@xxxxxxxxx> wrote:
> Il giorno 21 ago 2023, alle ore 20:13, Peter J. Holzer <hjp-pgsql@xxxxxx> 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@testdb LOG: execute <unnamed>: SET extra_float_digits = 3
>> 2023-08-21 11:51:50.634 CEST [1511] user@testdb LOG: execute <unnamed>: SET application_name = 'PostgreSQL JDBC Driver'
>> 2023-08-21 11:51:50.644 CEST [1511] user@testdb LOG: execute <unnamed>: SELECT dim1 FROM number WHERE name='first'
>> 2023-08-21 11:51:50.648 CEST [1511] user@testdb LOG: execute <unnamed>: SELECT dim1 FROM number WHERE name='first'
>> 2023-08-21 11:51:50.649 CEST [1511] user@testdb LOG: execute <unnamed>: SELECT dim1 FROM number WHERE name='first'
>> 2023-08-21 11:51:50.650 CEST [1511] user@testdb LOG: execute <unnamed>: SELECT dim1 FROM number WHERE name='first'
>> 2023-08-21 11:51:50.651 CEST [1511] user@testdb LOG: execute S_1: SELECT dim1 FROM number WHERE name='first'
>> 2023-08-21 11:51:50.651 CEST [1511] user@testdb LOG: execute S_1: SELECT dim1 FROM number WHERE name='first'
>> 2023-08-21 11:51:50.653 CEST [1511] user@testdb LOG: execute S_1: SELECT dim1 FROM number WHERE name='first'
>> 2023-08-21 11:51:50.653 CEST [1511] user@testdb LOG: execute S_1: SELECT dim1 FROM number WHERE name='first'
>> 2023-08-21 11:51:50.654 CEST [1511] user@testdb LOG: execute S_1: SELECT dim1 FROM number WHERE name='first'
>> 2023-08-21 11:51:50.656 CEST [1511] user@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.
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, Or remove double from binary transfer.
Regards,
Dave
