Fix badly formed Dets file after initialization

If a Dets table with fewer slots than keys was opened and then closed
after just a lookup, the contents were no longer well-formed. This bug
has been fixed. (Thanks to Matthew Evans.)

3 files changed, 43 insertions, 3 deletions

diff --git a/lib/stdlib/src/dets_v8.erl b/lib/stdlib/src/dets_v8.erl
index 1f9f84cd27..af36958c1c 100644
--- a/lib/stdlib/src/dets_v8.erl
+++ b/lib/stdlib/src/dets_v8.erl
@@ -1074,6 +1074,8 @@ wl([], _Type, Del, Lookup, I, Objs) ->
     [{Del, Lookup, Objs} | I].
 
 %% -> {NewHead, ok} | {NewHead, Error}
+may_grow(Head, 0, once) ->
+    {Head, ok};
 may_grow(Head, _N, _How) when Head#head.fixed =/= false ->
     {Head, ok};
 may_grow(#head{access = read}=Head, _N, _How) ->
diff --git a/lib/stdlib/src/dets_v9.erl b/lib/stdlib/src/dets_v9.erl
index 53238e962f..132af01f79 100644
--- a/lib/stdlib/src/dets_v9.erl
+++ b/lib/stdlib/src/dets_v9.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %% 
-%% Copyright Ericsson AB 2001-2009. All Rights Reserved.
+%% Copyright Ericsson AB 2001-2010. All Rights Reserved.
 %% 
 %% 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
@@ -1908,6 +1908,9 @@ write_cache(Head) ->
     end.
 
 %% -> {NewHead, ok} | {NewHead, Error}
+may_grow(Head, 0, once) ->
+    %% Do not re-hash if there is a chance that the file is not dirty.
+    {Head, ok};
 may_grow(Head, _N, _How) when Head#head.fixed =/= false ->
     {Head, ok};
 may_grow(#head{access = read}=Head, _N, _How) ->
diff --git a/lib/stdlib/test/dets_SUITE.erl b/lib/stdlib/test/dets_SUITE.erl
index a1f70dc27d..8b18ef5664 100644
--- a/lib/stdlib/test/dets_SUITE.erl
+++ b/lib/stdlib/test/dets_SUITE.erl
@@ -50,7 +50,8 @@
 	 otp_4208/1, otp_4989/1, many_clients/1, otp_4906/1, otp_5402/1,
          simultaneous_open/1, insert_new/1, repair_continuation/1,
          otp_5487/1, otp_6206/1, otp_6359/1, otp_4738/1, otp_7146/1,
-         otp_8070/1, otp_8856/1, otp_8898/1, otp_8899/1, otp_8903/1]).
+         otp_8070/1, otp_8856/1, otp_8898/1, otp_8899/1, otp_8903/1,
+         otp_8923/1]).
 
 -export([dets_dirty_loop/0]).
 
@@ -108,7 +109,8 @@ all(suite) ->
 	      cache_duplicate_bags_v9, otp_4208, otp_4989, many_clients,
               otp_4906, otp_5402, simultaneous_open, insert_new, 
               repair_continuation, otp_5487, otp_6206, otp_6359, otp_4738,
-              otp_7146, otp_8070, otp_8856, otp_8898, otp_8899, otp_8903]}
+              otp_7146, otp_8070, otp_8856, otp_8898, otp_8899, otp_8903,
+              otp_8923]}
     end.
 
 not_run(suite) -> [];
@@ -3805,6 +3807,39 @@ otp_8903(Config) when is_list(Config) ->
     file:delete(File),
     ok.
 
+otp_8923(doc) ->
+    ["OTP-8923. rehash due to lookup after initialization."];
+otp_8923(suite) ->
+    [];
+otp_8923(Config) when is_list(Config) ->
+    Tab = otp_8923,
+    File = filename(Tab, Config),
+    %% Create a file with more than 256 keys:
+    file:delete(File),
+    Bin = list_to_binary([ 0 || _ <- lists:seq(1, 400) ]),
+    BigBin = list_to_binary([ 0 ||_ <- lists:seq(1, 4000)]),
+    Ets = ets:new(temp, [{keypos,1}]),
+    ?line [ true = ets:insert(Ets, {C,Bin}) || C <- lists:seq(1, 700) ],
+    ?line true = ets:insert(Ets, {helper_data,BigBin}),
+    ?line true = ets:insert(Ets, {prim_btree,BigBin}),
+    ?line true = ets:insert(Ets, {sec_btree,BigBin}),
+    %% Note: too few slots; re-hash will take place
+    ?line {ok, Tab} = dets:open_file(Tab, [{file,File}]),
+    ?line Tab = ets:to_dets(Ets, Tab),
+    ?line ok = dets:close(Tab),
+    ?line true = ets:delete(Ets),
+    
+    ?line {ok,Ref} = dets:open_file(File),
+    ?line [{1,_}] = dets:lookup(Ref, 1),
+    ?line ok = dets:close(Ref),
+
+    ?line {ok,Ref2} = dets:open_file(File),
+    ?line [{helper_data,_}] = dets:lookup(Ref2, helper_data),
+    ?line ok = dets:close(Ref2),
+
+    file:delete(File),
+    ok.
+
 %%
 %% Parts common to several test cases
 %%