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vatamane pushed a commit to branch main
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The following commit(s) were added to refs/heads/main by this push:
new a6fc3f1f3 Fix mem3_util overlapping shards
a6fc3f1f3 is described below
commit a6fc3f1f33650860e5004a568dc78306d92f4bd5
Author: Nick Vatamaniuc <[email protected]>
AuthorDate: Wed May 7 11:26:32 2025 -0400
Fix mem3_util overlapping shards
Previously we started the {min, max} accumulator as {0, ?RANGE_END} while it
should have been `{?RANGE_END, 0}` so during the fold they'd be reduced to
the
actual min/max seen in the list of shards.
Another bug was that the unit test was never run as it didn't end in `_`
and it
emitted test generators `?_assertEqual(...)` so make sure the test runs and
add
a few cases: empty list of shards and when range doesn't start or end at
`0` or
`?RANGE_END`.
Thanks to @rnewson for finding the bug!
---
src/mem3/src/mem3_util.erl | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)
diff --git a/src/mem3/src/mem3_util.erl b/src/mem3/src/mem3_util.erl
index 520f54629..0ff22f07f 100644
--- a/src/mem3/src/mem3_util.erl
+++ b/src/mem3/src/mem3_util.erl
@@ -469,13 +469,15 @@ range_overlap([A, B], [X, Y]) when
->
A =< Y andalso X =< B.
-non_overlapping_shards(Shards) ->
+non_overlapping_shards([]) ->
+ [];
+non_overlapping_shards([_ | _] = Shards) ->
{Start, End} = lists:foldl(
fun(Shard, {Min, Max}) ->
[B, E] = mem3:range(Shard),
{min(B, Min), max(E, Max)}
end,
- {0, ?RING_END},
+ {?RING_END, 0},
Shards
),
non_overlapping_shards(Shards, Start, End).
@@ -705,10 +707,11 @@ range_overlap_test_() ->
]
].
-non_overlapping_shards_test() ->
+non_overlapping_shards_test_() ->
[
?_assertEqual(Res, non_overlapping_shards(Shards))
|| {Shards, Res} <- [
+ {[], []},
{
[shard(0, ?RING_END)],
[shard(0, ?RING_END)]
@@ -719,7 +722,7 @@ non_overlapping_shards_test() ->
},
{
[shard(0, 1), shard(0, 1)],
- [shard(0, 1)]
+ [shard(0, 1), shard(0, 1)]
},
{
[shard(0, 1), shard(3, 4)],
@@ -731,15 +734,15 @@ non_overlapping_shards_test() ->
},
{
[shard(1, 2), shard(0, 1)],
- [shard(0, 1), shard(1, 2)]
+ []
},
{
[shard(0, 1), shard(0, 2), shard(2, 5), shard(3, 5)],
- [shard(0, 2), shard(2, 5)]
+ [shard(0, 2), shard(3, 5)]
},
{
- [shard(0, 2), shard(4, 5), shard(1, 3)],
- []
+ [shard(1, 2), shard(3, 4), shard(1, 4), shard(5, 6)],
+ [shard(1, 4), shard(5, 6)]
}
]
].
