mnesia_schema.erl

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%% ``The contents of this file are subject to the Erlang Public License,
%% Version 1.1, (the "License"); you may not use this file except in
%% compliance with the License. You should have received a copy of the
%% Erlang Public License along with this software. If not, it can be
%% retrieved via the world wide web at http://www.erlang.org/.
%% 
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%% the License for the specific language governing rights and limitations
%% under the License.
%% 
%% The Initial Developer of the Original Code is Ericsson Utvecklings AB.
%% Portions created by Ericsson are Copyright 1999, Ericsson Utvecklings
%% AB. All Rights Reserved.''
%% 
%%     $Id$
%%
%% In this module we provide a number of explicit functions
%% to maninpulate the schema. All these functions are called
%% within a special schema transaction.
%%
%% We also have an init/1 function defined here, this func is
%% used by mnesia:start() to initialize the entire schema.

-module(mnesia_schema).

-export([
         add_snmp/2,
         add_table_copy/3,
         add_table_index/2,
	 arrange_restore/3,
         attr_tab_to_pos/2,
         attr_to_pos/2,
         change_table_copy_type/3,
         change_table_access_mode/2,
         change_table_load_order/2,
	 change_table_frag/2,
	 clear_table/1,
         create_table/1,
	 cs2list/1,
         del_snmp/1,
         del_table_copy/2,
         del_table_index/2,
         delete_cstruct/2,
         delete_schema/1,
         delete_schema2/0,
         delete_table/1,
         delete_table_property/2,
         dump_tables/1,
         ensure_no_schema/1,
	 get_create_list/1,
         get_initial_schema/2,
	 get_table_properties/1,
         info/0,
         info/1,
         init/1,
         insert_cstruct/3,
	 is_remote_member/1,
         list2cs/1,
         lock_schema/0,
         merge_schema/0,
         move_table/3,
         opt_create_dir/2,
         prepare_commit/3,
         purge_dir/2,
         purge_tmp_files/0,
         ram_delete_table/2,
%         ram_delete_table/3,
	 read_cstructs_from_disc/0,
         read_nodes/0,
         remote_read_schema/0,
	 restore/1,
         restore/2,
         restore/3,
	 schema_coordinator/3,
	 set_where_to_read/3,
         transform_table/4,
         undo_prepare_commit/2,
         unlock_schema/0,
         version/0,
         write_table_property/2
        ]).

%% Exports for mnesia_frag
-export([
	 get_tid_ts_and_lock/2,
	 make_create_table/1,
         ensure_active/1,
	 pick/4,
	 verify/3,
	 incr_version/1,
	 check_keys/3,
	 check_duplicates/2,
	 make_delete_table/2
	]).

%% Needed outside to be able to use/set table_properties
%% from user (not supported) 
-export([schema_transaction/1,
	 insert_schema_ops/2,
	 do_create_table/1,
	 do_delete_table/1,
	 do_read_table_property/2,
	 do_delete_table_property/2,
 	 do_write_table_property/2]).

-include("mnesia.hrl").
-include_lib("kernel/include/file.hrl").

-import(mnesia_lib, [set/2, del/2, verbose/2, dbg_out/2]).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Here comes the init function which also resides in
%% this module, it is called upon by the trans server
%% at startup of the system
%% 
%% We have a meta table which looks like
%% {table, schema, 
%%    {type, set},
%%    {disc_copies, all},
%%    {arity, 2}
%%    {attributes, [key, val]}
%%
%% This means that we have a series of {schema, Name, Cs} tuples
%% in a table called schema !!

init(IgnoreFallback) ->
    Res = read_schema(true, IgnoreFallback),
    {ok, Source, _CreateList} = exit_on_error(Res),
    verbose("Schema initiated from: ~p~n", [Source]),
    set({schema, tables}, []),
    set({schema, local_tables}, []),
    Tabs = set_schema(?ets_first(schema)),
    lists:foreach(fun(Tab) -> clear_whereabouts(Tab) end, Tabs),
    set({schema, where_to_read}, node()),
    set({schema, load_node}, node()),
    set({schema, load_reason}, initial),
    mnesia_controller:add_active_replica(schema, node()).

exit_on_error({error, Reason}) ->
    exit(Reason);
exit_on_error(GoodRes) ->
    GoodRes.

val(Var) ->
    case ?catch_val(Var) of
	{'EXIT', Reason} -> mnesia_lib:other_val(Var, Reason); 
	Value -> Value 
    end.

%% This function traverses all cstructs in the schema and
%% sets all values in mnesia_gvar accordingly for each table/cstruct

set_schema('$end_of_table') -> 
    [];
set_schema(Tab) ->
    do_set_schema(Tab),
    [Tab | set_schema(?ets_next(schema, Tab))].

get_create_list(Tab) ->
    ?ets_lookup_element(schema, Tab, 3).

do_set_schema(Tab) ->
    List = get_create_list(Tab),
    Cs = list2cs(List),
    do_set_schema(Tab, Cs).

do_set_schema(Tab, Cs) ->
    Type = Cs#cstruct.type,
    set({Tab, setorbag}, Type),
    set({Tab, local_content}, Cs#cstruct.local_content),
    set({Tab, ram_copies}, Cs#cstruct.ram_copies),
    set({Tab, disc_copies}, Cs#cstruct.disc_copies),
    set({Tab, disc_only_copies}, Cs#cstruct.disc_only_copies),
    set({Tab, load_order}, Cs#cstruct.load_order),
    set({Tab, access_mode}, Cs#cstruct.access_mode),
    set({Tab, snmp}, Cs#cstruct.snmp),
    set({Tab, user_properties}, Cs#cstruct.user_properties),
    [set({Tab, user_property, element(1, P)}, P) || P <- Cs#cstruct.user_properties],
    set({Tab, frag_properties}, Cs#cstruct.frag_properties),
    mnesia_frag:set_frag_hash(Tab, Cs#cstruct.frag_properties),
    set({Tab, attributes}, Cs#cstruct.attributes),
    Arity = length(Cs#cstruct.attributes) + 1,
    set({Tab, arity}, Arity),
    RecName =  Cs#cstruct.record_name,
    set({Tab, record_name}, RecName),
    set({Tab, record_validation}, {RecName, Arity, Type}),
    set({Tab, wild_pattern}, wild(RecName, Arity)),
    set({Tab, index}, Cs#cstruct.index),
    %% create actual index tabs later
    set({Tab, cookie}, Cs#cstruct.cookie),
    set({Tab, version}, Cs#cstruct.version),
    set({Tab, cstruct}, Cs),
    Storage = mnesia_lib:schema_cs_to_storage_type(node(), Cs),
    set({Tab, storage_type}, Storage),
    mnesia_lib:add({schema, tables}, Tab),
    Ns = mnesia_lib:cs_to_nodes(Cs),
    case lists:member(node(), Ns) of
        true ->
            mnesia_lib:add({schema, local_tables}, Tab);
        false when Tab == schema ->
            mnesia_lib:add({schema, local_tables}, Tab);
        false ->
            ignore
    end.

wild(RecName, Arity) ->
    Wp0 = list_to_tuple(lists:duplicate(Arity, '_')),
    setelement(1, Wp0, RecName).

%% Temporarily read the local schema and return a list
%% of all nodes mentioned in the schema.DAT file
read_nodes() ->
    %% Ensure that we access the intended Mnesia
    %% directory. This function may not be called
    %% during startup since it will cause the
    %% application_controller to get into deadlock
    case mnesia_lib:ensure_loaded(?APPLICATION) of
	ok ->
	    case read_schema(false) of
		{ok, _Source, CreateList} ->
		    Cs = list2cs(CreateList),
		    {ok, Cs#cstruct.disc_copies ++ Cs#cstruct.ram_copies};
		{error, Reason} ->
		    {error, Reason}
	    end;
	{error, Reason} ->
	    {error, Reason}
    end.

%% Returns Version from the tuple {Version,MasterNodes}
version() ->
    case read_schema(false) of
        {ok, Source, CreateList} when Source /= default ->
	    Cs = list2cs(CreateList),
            {Version, _Details} = Cs#cstruct.version,
            Version;
        _ ->
            case dir_exists(mnesia_lib:dir()) of
                true -> {1,0};
                false -> {0,0}
            end
    end.

%% Calculate next table version from old cstruct
incr_version(Cs) ->
    {{Major, Minor}, _} = Cs#cstruct.version,
    Nodes = mnesia_lib:intersect(val({schema, disc_copies}),
                                 mnesia_lib:cs_to_nodes(Cs)), 
    V = 
        case Nodes -- val({Cs#cstruct.name, active_replicas}) of
            [] -> {Major + 1, 0};    % All replicas are active
            _ -> {Major, Minor + 1}  % Some replicas are inactive
        end,
    Cs#cstruct{version = {V, {node(), now()}}}.

%% Returns table name
insert_cstruct(Tid, Cs, KeepWhereabouts) ->
    Tab = Cs#cstruct.name,
    TabDef = cs2list(Cs),
    Val = {schema, Tab, TabDef},
    mnesia_checkpoint:tm_retain(Tid, schema, Tab, write),
    mnesia_subscr:report_table_event(schema, Tid, Val, write),
    Active = val({Tab, active_replicas}),

    case KeepWhereabouts of
        true ->
            ignore;
        false when Active == [] ->
            clear_whereabouts(Tab);
        false ->
            %% Someone else has initiated table
            ignore
    end,
    set({Tab, cstruct}, Cs),
    ?ets_insert(schema, Val),
    do_set_schema(Tab, Cs),
    Val.

clear_whereabouts(Tab) ->
    set({Tab, checkpoints}, []),
    set({Tab, subscribers}, []),
    set({Tab, where_to_read}, nowhere),
    set({Tab, active_replicas}, []),
    set({Tab, commit_work}, []),
    set({Tab, where_to_write}, []),
    set({Tab, where_to_commit}, []),
    set({Tab, load_by_force}, false),
    set({Tab, load_node}, unknown),
    set({Tab, load_reason}, unknown).

%% Returns table name
delete_cstruct(Tid, Cs) ->
    Tab = Cs#cstruct.name,
    TabDef = cs2list(Cs),
    Val = {schema, Tab, TabDef},
    mnesia_checkpoint:tm_retain(Tid, schema, Tab, delete),
    mnesia_subscr:report_table_event(schema, Tid, Val, delete),
    mnesia_controller:update(
      fun() ->
	      ?ets_match_delete(mnesia_gvar, {{Tab, '_'}, '_'}),
	      ?ets_match_delete(mnesia_gvar, {{Tab, '_', '_'}, '_'}),
	      del({schema, local_tables}, Tab),
	      del({schema, tables}, Tab),
	      ?ets_delete(schema, Tab)
      end),
    Val.

%% Delete the Mnesia directory on all given nodes
%% Requires that Mnesia is not running anywhere
%% Returns ok | {error,Reason}
delete_schema(Ns) when list(Ns), Ns /= [] ->
    RunningNs = mnesia_lib:running_nodes(Ns),
    Reason = "Cannot delete schema on all nodes",
    if
        RunningNs == [] ->
	    case rpc:multicall(Ns, ?MODULE, delete_schema2, []) of
		{Replies, []} ->
		    case [R || R <- Replies, R /= ok]  of
			[] ->
			    ok;
			BadReplies ->
			    verbose("~s: ~p~n", [Reason, BadReplies]),
			    {error, {"All nodes not running", BadReplies}}
		    end;
		{_Replies, BadNs} ->
                    verbose("~s: ~p~n", [Reason, BadNs]),
                    {error, {"All nodes not running", BadNs}}
            end;
        true ->
            verbose("~s: ~p~n", [Reason, RunningNs]),
            {error, {"Mnesia is not stopped everywhere", RunningNs}}
    end;
delete_schema(Ns) ->
    {error, {badarg, Ns}}.

delete_schema2() ->
    %% Ensure that we access the intended Mnesia
    %% directory. This function may not be called
    %% during startup since it will cause the
    %% application_controller to get into deadlock
    case mnesia_lib:ensure_loaded(?APPLICATION) of
	ok ->
	    case mnesia_lib:is_running() of
		no ->
		    Dir = mnesia_lib:dir(),
		    purge_dir(Dir, []),
		    ok;
		_ ->
		    {error, {"Mnesia still running", node()}}
	    end;
	{error, Reason} ->
	    {error, Reason}
    end.
    
ensure_no_schema([H|T]) when atom(H) ->
    case rpc:call(H, ?MODULE, remote_read_schema, []) of
        {badrpc, Reason} ->
            {H, {"All nodes not running", H, Reason}};
        {ok,Source, _} when Source /= default ->
            {H, {already_exists, H}};
        _ ->
            ensure_no_schema(T)
    end;
ensure_no_schema([H|_]) ->
    {error,{badarg, H}};
ensure_no_schema([]) ->
    ok.

remote_read_schema() ->
    %% Ensure that we access the intended Mnesia
    %% directory. This function may not be called
    %% during startup since it will cause the
    %% application_controller to get into deadlock
    case mnesia_lib:ensure_loaded(?APPLICATION) of
	ok ->
	    case mnesia_monitor:get_env(schema_location) of
		opt_disc ->
		    read_schema(false);
		_ ->
		    read_schema(false)
	    end;
	{error, Reason} ->
	    {error, Reason}
    end.

dir_exists(Dir) ->
    dir_exists(Dir, mnesia_monitor:use_dir()).
dir_exists(Dir, true) ->
    case file:read_file_info(Dir) of
        {ok, _} -> true;
        _ -> false
    end;
dir_exists(_Dir, false) ->
    false.

opt_create_dir(UseDir, Dir) when UseDir == true->
    case dir_exists(Dir, UseDir) of
        true ->
            check_can_write(Dir);
        false ->
            case file:make_dir(Dir) of
                ok ->