nickva commented on a change in pull request #1972: Introduce Shard Splitting
To CouchDB
URL: https://github.com/apache/couchdb/pull/1972#discussion_r270163090
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File path: src/mem3/src/mem3_rep.erl
##########
@@ -369,58 +414,92 @@ calculate_start_seq(Acc) ->
Seq = TargetSeq,
History = couch_util:get_value(<<"history">>, TProps, {[]})
end,
- Acc1#acc{seq = Seq, history = History};
+ Tgt1#tgt{seq = Seq, history = History};
{not_found, _} ->
- compare_epochs(Acc1)
+ compare_epochs(Db, Tgt1)
end.
-compare_epochs(Acc) ->
+
+push_changes(#acc{} = Acc0) ->
#acc{
- db = Db,
- target = #shard{node=Node, name=Name}
- } = Acc,
+ db = Db0,
+ seq = Seq
+ } = Acc0,
+
+ % Avoid needless rewriting the internal replication
+ % checkpoint document if nothing is replicated.
+ UpdateSeq = couch_db:get_update_seq(Db0),
+ if Seq < UpdateSeq -> ok; true ->
+ throw({finished, 0})
+ end,
+
+ with_src_db(Acc0, fun(Db) ->
+ Acc1 = Acc0#acc{db = Db},
+ Fun = fun ?MODULE:changes_enumerator/2,
+ {ok, Acc2} = couch_db:fold_changes(Db, Seq, Fun, Acc1),
+ {ok, #acc{seq = LastSeq}} = replicate_batch_multi(Acc2),
+ {ok, couch_db:count_changes_since(Db, LastSeq)}
+ end).
+
+
+compare_epochs(Db, #tgt{shard = TgtShard} = Tgt) ->
+ #shard{node = Node, name = Name} = TgtShard,
UUID = couch_db:get_uuid(Db),
Epochs = couch_db:get_epochs(Db),
Seq = mem3_rpc:find_common_seq(Node, Name, UUID, Epochs),
- Acc#acc{seq = Seq, history = {[]}}.
+ Tgt#tgt{seq = Seq, history = {[]}}.
+
changes_enumerator(#doc_info{id=DocId}, #acc{db=Db}=Acc) ->
{ok, FDI} = couch_db:get_full_doc_info(Db, DocId),
changes_enumerator(FDI, Acc);
-changes_enumerator(#full_doc_info{}=FDI, #acc{revcount=C, infos=Infos}=Acc0) ->
- #doc_info{
- high_seq=Seq,
- revs=Revs
- } = couch_doc:to_doc_info(FDI),
- {Count, NewInfos} = case filter_doc(Acc0#acc.filter, FDI) of
- keep -> {C + length(Revs), [FDI | Infos]};
- discard -> {C, Infos}
+changes_enumerator(#full_doc_info{}=FDI, #acc{}=Acc0) ->
+ #acc{revcount = C, targets = Targets0, hashfun = HashFun} = Acc0,
+ #doc_info{high_seq=Seq, revs=Revs} = couch_doc:to_doc_info(FDI),
+ {Count, Targets} = case filter_doc(Acc0#acc.filter, FDI) of
+ keep -> {C + length(Revs), changes_append_fdi(FDI, Targets0, HashFun)};
+ discard -> {C, Targets0}
end,
- Acc1 = Acc0#acc{
- seq=Seq,
- revcount=Count,
- infos=NewInfos
- },
+ Acc1 = Acc0#acc{seq = Seq, revcount = Count, targets = Targets},
Go = if Count < Acc1#acc.batch_size -> ok; true -> stop end,
{Go, Acc1}.
-replicate_batch(#acc{target = #shard{node=Node, name=Name}} = Acc) ->
- case find_missing_revs(Acc) of
- [] ->
- ok;
- Missing ->
- lists:map(fun(Chunk) ->
- Docs = open_docs(Acc, Chunk),
+changes_append_fdi(#full_doc_info{id = Id} = FDI, Targets, HashFun) ->
+ case mem3_reshard_job:pickfun(Id, maps:keys(Targets), HashFun) of
+ not_in_range ->
+ Targets;
Review comment:
Yeah for cases where we replicate from [0, 10] -> [5, 15] we'd only want to
send 5, 10 docs to [5, 15] range. This won't technically happen until we have
shard merging
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