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From jianqiao <...@git.apache.org>
Subject [GitHub] incubator-quickstep pull request #19: Improve text scan operator
Date Thu, 09 Jun 2016 15:11:30 GMT
Github user jianqiao commented on a diff in the pull request:

    --- Diff: relational_operators/TextScanOperator.cpp ---
    @@ -274,439 +116,293 @@ TextScanWorkOrder::TextScanWorkOrder(const std::size_t query_id,
     void TextScanWorkOrder::execute() {
       const CatalogRelationSchema &relation = output_destination_->getRelation();
    +  std::vector<Tuple> tuples;
    -  string current_row_string;
    -  if (is_file_) {
    -    FILE *file = std::fopen(filename_.c_str(), "r");
    -    if (file == nullptr) {
    -      throw TextScanReadError(filename_);
    -    }
    +  constexpr std::size_t kSmallBufferSize = 0x4000;
    --- End diff --
    From experiments this is the best size for both _slowdisk_ and _fastdisk_ on the cloudlab
machines. The observation is that _slowdisk_ loading favors smaller (256K) segment size and
_fastdisk_ loading favors larger (1M~4M, but 256K is okay) segment size. I haven't dived into
the underlying details though.

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