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db: improve make_local_reader()

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Instead of merging shard data using make_combined_reader(), take advantage
of the fact that shard data is disjoint, and use make_joining_reader().
This removes the need to sort the partitions as they are being read.
This commit is contained in:
Avi Kivity
2015-08-04 17:11:39 +03:00
parent 951eef2945
commit 8d050b679a
1 changed files with 4 additions and 2 deletions
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6
service/storage_proxy.cc
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@@ -3167,13 +3167,15 @@ public:
mutation_reader
storage_proxy::make_local_reader(utils::UUID cf_id, const query::partition_range& range) {
unsigned first_shard = range.start() ? dht::shard_of(range.start()->value().token()) : 0;
unsigned last_shard = range.end() ? dht::shard_of(range.end()->value().token()) : smp::count - 1;
std::vector<mutation_reader> readers;
for (unsigned cpu : smp::all_cpus()) {
for (auto cpu = first_shard; cpu <= last_shard; ++cpu) {
readers.emplace_back([reader = make_lw_shared<shard_reader>(cf_id, _db, cpu, range)] () mutable {
return (*reader)();
});
}
return make_combined_reader(std::move(readers));
return make_joining_reader(std::move(readers));
}
}