thevar1able/ClickHouse
1
0
Fork 0
mirror of https://github.com/ClickHouse/ClickHouse.git synced 2024-09-21 09:10:48 +00:00
Code Issues Packages Projects Releases Wiki Activity

added comments

Browse Source
This commit is contained in:
Nikolai Kochetov 2017-07-21 21:02:02 +03:00
parent c64b65ee29
commit bc0921a64e
1 changed files with 4 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
dbms/src/Storages/MergeTree/MergeTreeBaseBlockInputStream.cpp
View File

@ -87,15 +87,19 @@ Block MergeTreeBaseBlockInputStream::readFromPart()
if (!task.size_predictor) if (!task.size_predictor)
return max_block_size_rows; return max_block_size_rows;
/// Limit in rows, calculated by preferred_max_column_in_block_size_bytes. Can't be less than index_granularity.
size_t rows_to_read = std::max(index_granularity, task.size_predictor->estimateNumRows(preferred_block_size_bytes)); size_t rows_to_read = std::max(index_granularity, task.size_predictor->estimateNumRows(preferred_block_size_bytes));
if (preferred_max_column_in_block_size_bytes) if (preferred_max_column_in_block_size_bytes)
{ {
/// Limit in rows, calculated by preferred_max_column_in_block_size_bytes.
size_t rows_to_read_for_max_size_column size_t rows_to_read_for_max_size_column
= task.size_predictor->estimateNumRowsForMaxSizeColumn(preferred_max_column_in_block_size_bytes); = task.size_predictor->estimateNumRowsForMaxSizeColumn(preferred_max_column_in_block_size_bytes);
double filtration_ratio = std::max(min_filtration_ratio, 1.0 - task.size_predictor->filtered_rows_ratio); double filtration_ratio = std::max(min_filtration_ratio, 1.0 - task.size_predictor->filtered_rows_ratio);
size_t rows_to_read_for_max_size_column_with_filtration size_t rows_to_read_for_max_size_column_with_filtration
= static_cast<size_t>(rows_to_read_for_max_size_column / filtration_ratio); = static_cast<size_t>(rows_to_read_for_max_size_column / filtration_ratio);
/// If preferred_max_column_in_block_size_bytes is used, number of rows to read can be less than index_granularity.
rows_to_read = std::min(rows_to_read, rows_to_read_for_max_size_column_with_filtration); rows_to_read = std::min(rows_to_read, rows_to_read_for_max_size_column_with_filtration);
} }