Erlang and PostgreSQL - postgresql

Question

I try to execute simple PostgreSQL query with erlang and epgsql.
I do:
{ok, C} = pgsql:connect("localhost", "shk", "qwerty", [{database, "mydb"}]).
>> {ok,<0.34.0>}
Then:
{ok, Cols, Rows} = pgsql:squery(C, "select * from users").
But i got error:
=ERROR REPORT==== 27-Apr-2012::17:58:23 ===
** State machine <0.34.0> terminating
** Last message in was {'EXIT',<0.32.0>,
{{badmatch,
{error,
{error,'ð\236ð¨ð\230ð\221ð\232ð\220',<<"42P01">>,
<<208,190,209,130,208,189,208,190,209,136,208,181,
208,189,208,184,208,181,32,34,109,121,100,98,34,
32,208,189,208,181,32,209,129,209,131,209,137,
208,181,209,129,209,130,208,178,209,131,208,181,
209,130>>,
[{position,<<"15">>}]}}},
[{erl_eval,expr,3}]}}
** When State == ready
** Data == {state,undefined,<0.35.0>,5000,
[{<<"application_name">>,<<>>},
{<<"client_encoding">>,<<"UTF8">>},
{<<"DateStyle">>,<<"ISO, DMY">>},
{<<"integer_datetimes">>,<<"on">>},
{<<"IntervalStyle">>,<<"postgres">>},
{<<"is_superuser">>,<<"off">>},
{<<"server_encoding">>,<<"UTF8">>},
{<<"server_version">>,<<"9.0.7">>},
{<<"session_authorization">>,<<"shk">>},
{<<"standard_conforming_strings">>,<<"off">>},
{<<"TimeZone">>,<<"posixrules">>}],
undefined,undefined,undefined,
{30932,488494147},
{statement,undefined,undefined,undefined},
73}
** Reason for termination =
** {{badmatch,{error,{error,'ð\236ð¨ð\230ð\221ð\232ð\220',<<"42P01">>,
<<208,190,209,130,208,189,208,190,209,136,208,181,
208,189,208,184,208,181,32,34,109,121,100,98,34,
32,208,189,208,181,32,209,129,209,131,209,137,
208,181,209,129,209,130,208,178,209,131,208,181,
209,130>>,
[{position,<<"15">>}]}}},
[{erl_eval,expr,3}]}
What's wrong i do? How can i fix it?
Thank you.

Answer 1

The error string seems to be in russian if I recognize the characters.
To view the response you can use the following command:
io:format("~ts",[<<208,190,209,130,208,189,208,190,209,136,208,181,
208,189,208,184,208,181,32,34,109,121,100,98,34,
32,208,189,208,181,32,209,129,209,131,209,137,
208,181,209,129,209,130,208,178,209,131,208,181,
209,130>>]).
отношение "mydb" не существует
A quick google translate makes me think the database mydb does not exist or you do not have permissions to use it.

Answer 2

try simply doing
Response = pgsql:squery(C, "select * from mydb"),
io:format("~p~n",[Response]).
And see what he is giving back from the server, maybe you have typo or table don't exists etc.
also check this out http://www.erlangatwork.com/2009/01/erlang-and-postgresql.html

Answer 3

From epgsql docs:
Errors
Errors originating from the PostgreSQL backend are returned as {error, #error{}},
see pgsql.hrl for the record definition. epgsql functions may also return
{error, What} where What is one of the following:
{unsupported_auth_method, Method} - required auth method is unsupported
timeout - request timed out
closed - connection was closed
sync_required - error occured and pgsql:sync must be called
Try to include pgsql.hrl, capture the error and print the error message, that should point you to the right direction.