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CompactionFilterV2: eliminate an often unnecessary allocation.

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If a compaction filter implementation is simply filtering values, then
allocating the "changed values" bitmap is an extra memory allocation
that adds no value. Additionally, the compaction implementation has to
do marginally more work to calculate the offset into the bitmap
(vector<bool> specialization) for each record the filter did not mark
for deletion.

Explicitly handle the case where compact_->value_changed_buf_ is empty.
This commit is contained in:
maurice barnum 2014-11-05 05:31:11 +00:00
parent 29a9161f34
commit 76f6c7c7c4
1 changed files with 4 additions and 2 deletions
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6
db/compaction_job.cc
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@ -890,7 +890,8 @@ void CompactionJob::CallCompactionFilterV2(
assert(compact_->to_delete_buf_.size() == compact_->key_str_buf_.size());
assert(compact_->to_delete_buf_.size() ==
compact_->existing_value_str_buf_.size());
assert(compact_->to_delete_buf_.size() ==
assert(compact_->value_changed_buf_.empty() ||
compact_->to_delete_buf_.size() ==
compact_->value_changed_buf_.size());
int new_value_idx = 0;
@ -905,7 +906,8 @@ void CompactionJob::CallCompactionFilterV2(
// no value associated with delete
compact_->existing_value_str_buf_[i].clear();
RecordTick(stats_, COMPACTION_KEY_DROP_USER);
} else if (compact_->value_changed_buf_[i]) {
} else if (!compact_->value_changed_buf_.empty() &&
compact_->value_changed_buf_[i]) {
compact_->existing_value_str_buf_[i] =
compact_->new_value_buf_[new_value_idx++];
}