| Author |
Message |
< Advanced Erlang/OTP ~ Problems getting Mnesia Ref Manual Example working |
| brett hallett |
 Posted: Tue Aug 21, 2007 12:30 am |
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User
Joined: 21 Aug 2007
Posts: 21
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Hi,
I'm trying to get the example shown in "Mnesia Database Managment System (Mnesia) version 4.3" manual
1.2.2 page 5 .. etc.. working.
(BTW this section is NOT very clear !), for example, its not at all clear whether you should enter the "insert_emp" code directly into
the erl session or create a seperate function on a file ( I chose to file it)
All appears to go well until step ">7" below in the execution script, where Mnsesia cannot find the record structures,
which I've just defined -- I think !!
Can someone please advise my on where I'm going wrong ?
Thank you,
Brett
====================
I created a number of files thus:
=== file === company.hrl
-record(employee, {emp_no,
name,
salary,
sex,
phone,
room_no}).
-record(dept, {id,
name}).
-record(project, {name,
number}).
-record(manager, {emp,
dept}).
-record(at_dep, {emp,
dept_id}).
-record(in_proj, {emp,
proj_name}).
=== file === define.erl ==========
-module(define).
-export([init/0]).
-include("company.hrl").
init() ->
mnesia:create_table(employee,
[{attributes, record_info(fields, employee)}]),
mnesia:create_table(dept,
[{attributes, record_info(fields, dept)}]),
mnesia:create_table(project,
[{attributes, record_info(fields, project)}]),
mnesia:create_table(manager, [{type, bag},
{attributes, record_info(fields, manager)}]),
mnesia:create_table(at_dep,
[{attributes, record_info(fields, at_dep)}]),
mnesia:create_table(in_proj, [{type, bag},
{attributes, record_info(fields, in_proj)}]).
=== file === insert_command.txt ( to save retyping the commands 
Emp = #employee{emp_no=104732, name=klacke, salary=7, sex=male, phone= 989898, room_no = {221, 015}},
insert_emp(Brett, 'B/SFR', [Erlang, mnesia, opt ]).
================================================
execution transcript from konsole
================================================
=========================
$ erl -mnesia dir '"Mnesia.Company"'
Erlang (BEAM) emulator version 5.5 [source] [async-threads:0] [kernel-poll:false]
Eshell V5.5 (abort with ^G)
1> mnesia:create_schema([node()]).
ok
2> mnesia:start().
ok
3> c(define.erl).
{ok,define}
4> ======= < made a typo here so removed the error report
5> define:init().
{atomic,ok}
6> mnesia:info().
---> Processes holding locks <---
---> Processes waiting for locks <---
---> Participant transactions <---
---> Coordinator transactions <---
---> Uncertain transactions <---
---> Active tables <---
in_proj : with 0 records occupying 279 words of mem
at_dep : with 0 records occupying 279 words of mem
manager : with 0 records occupying 279 words of mem
project : with 0 records occupying 279 words of mem
dept : with 0 records occupying 279 words of mem
employee : with 0 records occupying 279 words of mem
schema : with 7 records occupying 1064 words of mem
===> System info in version "4.3.1", debug level = none <===
opt_disc. Directory "/home/brett/Erlang_Mnesia/Mnesia.Company" is used.
use fallback at restart = false
running db nodes = [nonode@nohost]
stopped db nodes = []
master node tables = []
remote = []
ram_copies = [at_dep,dept,employee,in_proj,manager,project]
disc_copies = [schema]
disc_only_copies = []
[{nonode@nohost,disc_copies}] = [schema]
[{nonode@nohost,ram_copies}] = [employee,dept,project,manager,at_dep,in_proj]
8 transactions committed, 0 aborted, 0 restarted, 6 logged to disc
0 held locks, 0 in queue; 0 local transactions, 0 remote
0 transactions waits for other nodes: []
ok
7> c(insert_emp).
./insert_emp.erl:5: record employee undefined
./insert_emp.erl:8: record at_dep undefined
./insert_emp.erl:16: record in_proj undefined
./insert_emp.erl:4: Warning: variable 'DeptId' is unused
./insert_emp.erl:15: Warning: variable 'ProjName' is unused
error
8>
=============== end ==============
--
Brett S Hallett
dragoncity@impulse.net.au |
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| khigia |
| Posted: Tue Aug 21, 2007 1:10 am |
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Joined: 27 Mar 2007
Posts: 52
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You didn't post the file "insert_emp.erl" so it's a bit tricky to guess what can be wrong  .
First thoughts, it could be a missing include header, or a path problem. |
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| brett hallett |
| Posted: Tue Aug 21, 2007 5:20 am |
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User
Joined: 21 Aug 2007
Posts: 21
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Sorry about that ! Hopefully its the same code as
shown in the manual.
======== insert_emp.erl ========
-module(insert).
-export([insert_emp/3, mk_projs/2 ]).
insert_emp(Emp, DeptId, ProjNames) ->
Ename = Emp#employee.name,
Fun = fun() ->
mnesia:write(Emp),
AtDep = #at_dep{emp = Ename, dept_id = DeptId},
mnesia:write(AtDep),
mk_projs(Ename, ProjNames)
end,
mnesia:transaction(Fun).
mk_projs(Ename, [ProjName|Tail]) ->
mnesia:write(#in_proj{emp = Ename, proj_name = ProjName}),
mk_projs(Ename, Tail);
mk_projs(_, []) -> ok.
================================= |
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| khigia |
| Posted: Tue Aug 21, 2007 6:48 am |
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Joined: 27 Mar 2007
Posts: 52
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Oups! I should have read the manual then
Anyway, have you try to add the include declaration in insert_emp.erl ? Because when you try to compile (with c(insert_emp) the compiler complains that it doesn't know the record.
Adding this line after module declaration should fix this:
-include("company.hrl"). |
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| brett hallett |
| Posted: Wed Aug 22, 2007 12:02 am |
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Joined: 21 Aug 2007
Posts: 21
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Well actually I'm working from the manual
However I must admitt that I assumed that as I was working interactively that prior definitions would have been defined
as compamy.hrl had been compiled in.
The manual code does not show all the necessary code
required for this example.
Thank you for your help, now I hopeto progress !
Cheers,
Brett |
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| smithjolin |
| Posted: Wed Jul 25, 2012 1:09 am |
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Joined: 25 Jul 2012
Posts: 11
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Station Using?? Ten collection inside of just 2009 item scene
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| vaitty |
| Posted: Thu Jul 26, 2012 2:14 am |
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| trapples |
| Posted: Wed Aug 01, 2012 7:48 am |
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| What you said it is so interesting. |
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