Erlang和PostgreSQL

Question

我尝试使用erlang和epgsql执行简单的PostgreSQL查询。

我做：

{ok, C} = pgsql:connect("localhost", "shk", "qwerty", [{database, "mydb"}]).
>> {ok,<0.34.0>}

然后：

{ok, Cols, Rows} = pgsql:squery(C, "select * from users").

但是我得到了错误：

=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}]}

我怎么了 我该如何解决？

谢谢。

Answer 1

如果我识别出字符，错误字符串似乎是俄语。

要查看响应，可以使用以下命令：

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

快速谷歌翻译使我认为数据库mydb不存在或您没有使用它的权限。

Answer 2

尝试简单地做

Response = pgsql:squery(C, "select * from mydb"), 
io:format("~p~n",[Response]).

并查看他从服务器还给了什么，也许您有错字或表格不存在等。

还可以查看此http://www.erlangatwork.com/2009/01/erlang-and-postgresql.html

Answer 3

从epgsql 文档 ：

失误

来自PostgreSQL后端的错误以{error，#error {}}的形式返回，有关记录的定义，请参见pgsql.hrl。 epgsql函数还可能返回{error，What}其中以下之一：

{unsupported_auth_method，方法}-不支持必需的auth方法超时-请求超时关闭-连接已关闭sync_required-发生错误，必须调用pgsql：sync

尝试包含pgsql.hrl，捕获错误并打印错误消息，这应该为您指明正确的方向。