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Optimize getPartitionEndRow for window function #6625

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merged 3 commits into from
Jan 11, 2023
Merged

Optimize getPartitionEndRow for window function #6625

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4313b67
optimize getPartitionEndRow if the partition end is very close
gengliqi Jan 11, 2023
f16d096
fix copy of columns
gengliqi Jan 11, 2023
2aebb9f
fix
gengliqi Jan 11, 2023
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22 changes: 16 additions & 6 deletions dbms/src/DataStreams/WindowBlockInputStream.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -124,13 +124,13 @@ Block WindowBlockInputStream::readImpl()
// Judge whether current_partition_row is end row of partition in current block
bool WindowTransformAction::isDifferentFromPrevPartition(UInt64 current_partition_row)
{
const auto reference_columns = inputAt(prev_frame_start);
const auto compared_columns = inputAt(partition_end);
const Columns & reference_columns = inputAt(prev_frame_start);
const Columns & compared_columns = inputAt(partition_end);

for (size_t i = 0; i < partition_column_indices.size(); ++i)
{
const auto reference_column = reference_columns[partition_column_indices[i]];
const auto * compared_column = compared_columns[partition_column_indices[i]].get();
const ColumnPtr & reference_column = reference_columns[partition_column_indices[i]];
const ColumnPtr & compared_column = compared_columns[partition_column_indices[i]];
if (window_description.partition_by[i].collator)
{
if (compared_column->compareAt(current_partition_row,
Expand Down Expand Up @@ -240,9 +240,19 @@ Int64 WindowTransformAction::getPartitionEndRow(size_t block_rows)
Int64 left = partition_end.row;
Int64 right = block_rows - 1;

while (left <= right)
// Compare several times first.
// It will benefit if the partition end is very close.
for (; left <= std::min(left + 2, right); ++left)
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Better add a comment to explain why + 2

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A magic number

{
Int64 middle = left + (right - left) / 2;
if (isDifferentFromPrevPartition(left))
{
return left;
}
}

while (left < right)
{
Int64 middle = (left + right) << 1;
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@mengxin9014 mengxin9014 Jan 11, 2023 •
edited
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Suggested change
Int64 middle = (left + right) << 1;
Int64 middle = left + (right - left) << 1;

if (isDifferentFromPrevPartition(middle))
{
right = middle - 1;
Expand Down