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reduce number of read rows while reading in reverse order

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CurtizJ 2019-07-27 03:33:47 +03:00
parent 60289cd764
commit 12dcfe1f25
1 changed files with 2 additions and 2 deletions
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4
dbms/src/Storages/MergeTree/MergeTreeDataSelectExecutor.cpp
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@ -826,8 +826,8 @@ BlockInputStreams MergeTreeDataSelectExecutor::spreadMarkRangesAmongStreamsPKOrd
auto split_ranges = [max_block_size](const auto & ranges, size_t rows_granularity, size_t num_marks_in_part) auto split_ranges = [max_block_size](const auto & ranges, size_t rows_granularity, size_t num_marks_in_part)
{ {
/// Constants is just a guess. /// Constants is just a guess.
const size_t min_rows_in_range = max_block_size * 4; const size_t min_rows_in_range = max_block_size;
const size_t max_num_ranges = 32; const size_t max_num_ranges = 64;
size_t min_marks_in_range = std::max( size_t min_marks_in_range = std::max(
(min_rows_in_range + rows_granularity - 1) / rows_granularity, (min_rows_in_range + rows_granularity - 1) / rows_granularity,