Added paginate function to help users paginate through database results.

rebar.config

@@ -6,7 +6,7 @@
 	    {parse_transform, import_as}
 ]}.
 {deps, [
-        {lager,         ".*",	{git, "git://github.com/basho/lager.git",			{tag, "2.0.1"}}},
+        {lager,         ".*",	{git, "git://github.com/basho/lager.git",			{tag, "2.0.2"}}},
         {erlando,	".*",	{git, "git://github.com/travelping/erlando.git", "HEAD"}},
 	{aleppo,	".*",	{git, "git://github.com/ChicagoBoss/aleppo.git",		{tag, "bef139e4c7"}}},
 	{bson,		".*",	{git, "git://github.com/mongodb/bson-erlang.git",		{tag, "6d3cc910ea"}}},

src/boss_db.erl

@@ -21,6 +21,7 @@
         find_last/4,
         count/1,
         count/2,
+        paginate/3,
         count/3,
         counter/1, 
         counter/2, 
@@ -65,10 +66,12 @@
 
 -define(DEFAULT_TIMEOUT, (30 * 1000)).
 -define(POOLNAME, boss_db_pool).
+-define(DEFAULT_PAGE_SIZE, 10).
 
 start(Options) ->
     AdapterName = proplists:get_value(adapter, Options, mock),
     Adapter     = list_to_atom(lists:concat(["boss_db_adapter_", AdapterName])),
+    lager:info("Start Database Adapter ~p options ~p", [Adapter, Options]),
     Adapter:start(Options),
     lists:foldr(fun(ShardOptions, Acc) ->
                 case proplists:get_value(db_shard_models, ShardOptions, []) of
@@ -257,6 +260,26 @@ counter(Key) ->
 counter(Key, Timeout) ->
     db_call({counter, Key}, Timeout).
 
+%% @spec paginate( Model::atom(), Conditions, Opts ) -> Value | {error, Reason}
+%% @doc Paginate through the results from boss_db:find.  Use `Opts' {page,
+%% PageNum} and {page_size, PageSize} to control which page to fetch,
+%% and how many results per page.  Page size defaults to 10.
+paginate(Model, Conditions, Opts) ->
+    CleanOpts  = proplists:delete(offset, proplists:delete(limit, Opts)),
+    Page       = proplists:get_value(page, Opts, 1),
+    PageSize   = proplists:get_value(page_size, Opts, ?DEFAULT_PAGE_SIZE),
+    OptList    = proplists:delete(page_size, proplists:delete(page, CleanOpts)) ++
+        [{offset, PageSize * (Page - 1)}, {limit, PageSize}],
+    Total      = boss_db:count(Model, Conditions),
+    TotalPages =  compute_total_pages(PageSize, Total),
+    {Page, TotalPages, boss_db:find(Model, Conditions, OptList)}.
+
+compute_total_pages(PageSize, Total) ->
+    Total div PageSize + case Total rem PageSize of
+                             0 -> 0;
+                             _ -> 1
+                         end.
+
 %% @spec incr( Id::string() ) -> integer()
 %% @doc Treat the record associated with `Id' as a counter and atomically increment its value by 1.
 incr(Key) ->

src/db_adapters/boss_db_adapter_mysql.erl

@@ -12,13 +12,13 @@ stop() ->
     ok.
 
 init(Options) ->
-    DBHost = proplists:get_value(db_host, Options, "localhost"),
-    DBPort = proplists:get_value(db_port, Options, 3306),
-    DBUsername = proplists:get_value(db_username, Options, "guest"),
-    DBPassword = proplists:get_value(db_password, Options, ""),
-    DBDatabase = proplists:get_value(db_database, Options, "test"),
+    DBHost       = proplists:get_value(db_host,     Options, "localhost"),
+    DBPort       = proplists:get_value(db_port,     Options, 3306),
+    DBUsername   = proplists:get_value(db_username, Options, "guest"),
+    DBPassword   = proplists:get_value(db_password, Options, ""),
+    DBDatabase   = proplists:get_value(db_database, Options, "test"),
     DBIdentifier = proplists:get_value(db_shard_id, Options, boss_pool),
-    Encoding = utf8,
+    Encoding     = utf8,
     mysql_conn:start_link(DBHost, DBPort, DBUsername, DBPassword, DBDatabase, 
         fun(_, _, _, _) -> ok end, Encoding, DBIdentifier).
 
@@ -35,7 +35,7 @@ find(Pid, Id) when is_list(Id) ->
                 [Row] ->
                     Columns = mysql:get_result_field_info(MysqlRes),
                     case boss_record_lib:ensure_loaded(Type) of
-                        true -> activate_record(Row, Columns, Type);
+                        true  -> activate_record(Row, Columns, Type);
                         false -> {error, {module_not_loaded, Type}}
                     end
             end;
@@ -274,7 +274,7 @@ build_insert_query(Record) ->
                 {[DBColumn|Attrs], [pack_value(TableId)|Vals]};
             ({A, V}, {Attrs, Vals}) ->
                 DBColumn = proplists:get_value(A, AttributeColumns),
-                Value = case boss_sql_lib:is_foreign_key(Type, A) of
+                Value    = case boss_sql_lib:is_foreign_key(Type, A) of
                     true ->
                         {_, _, _, ForeignId} = boss_sql_lib:infer_type_from_id(V),
                         ForeignId;
@@ -284,11 +284,13 @@ build_insert_query(Record) ->
                 {[DBColumn|Attrs], [pack_value(Value)|Vals]}
         end, {[], []}, Record:attributes()),
     ["INSERT INTO ", TableName, " (", 
-        string:join(Attributes, ", "),
+        string:join(escape_attr(Attributes), ", "),
         ") values (",
         string:join(Values, ", "),
         ")"
     ].
+escape_attr(Attrs) ->
+    [["`", Attr, "`"] || Attr <- Attrs].
 
 build_update_query(Record) ->
     {Type, TableName, IdColumn, TableId} = boss_sql_lib:infer_type_from_id(Record:id()),
@@ -306,7 +308,7 @@ build_update_query(Record) ->
                     _ ->
                         V
                 end,
-                [DBColumn ++ " = " ++ pack_value(Value)|Acc]
+                ["`"++DBColumn ++ "` = " ++ pack_value(Value)|Acc]
         end, [], Record:attributes()),
     ["UPDATE ", TableName, " SET ", string:join(Updates, ", "),
         " WHERE ", IdColumn, " = ", pack_value(TableId)].
@@ -397,7 +399,6 @@ pack_match_not(Key) ->
 
 pack_boolean_query(Values, Op) ->
     "('" ++ string:join(lists:map(fun(Val) -> Op ++ escape_sql(Val) end, Values), " ") ++ "' IN BOOLEAN MODE)".
-
 pack_set(Values) ->
     "(" ++ string:join(lists:map(fun pack_value/1, Values), ", ") ++ ")".
 
@@ -430,7 +431,7 @@ pack_value(undefined) ->
 pack_value(V) when is_binary(V) ->
     pack_value(binary_to_list(V));
 pack_value(V) when is_list(V) ->
-    "'" ++ escape_sql(V) ++ "'";
+    mysql:encode(V);
 pack_value({_, _, _} = Val) ->
 	pack_date(Val);    
 pack_value({{_, _, _}, {_, _, _}} = Val) ->
@@ -445,5 +446,6 @@ pack_value(false) ->
     "FALSE".
 
 fetch(Pid, Query) ->
+    lager:info("Query ~s", [iolist_to_binary(Query)]),
     mysql_conn:fetch(Pid, [Query], self()).