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Merge pull request #28266 from CurtizJ/fix-order-by-merge

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Fix order by for `Merge` tables with `optimize_read_in_order`
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alexey-milovidov 2021-08-28 01:15:40 +03:00 committed by GitHub
commit 4eef445df9
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3 changed files with 30 additions and 2 deletions
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5
src/Storages/StorageMerge.cpp
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@ -338,9 +338,10 @@ Pipe StorageMerge::read(
auto pipe = Pipe::unitePipes(std::move(pipes));
if (!pipe.empty())
if (!pipe.empty() && !query_info.input_order_info)
// It's possible to have many tables read from merge, resize(num_streams) might open too many files at the same time.
// Using narrowPipe instead.
// Using narrowPipe instead. But in case of reading in order of primary key, we cannot do it,
// because narrowPipe doesn't preserve order.
narrowPipe(pipe, num_streams);
return pipe;

5
tests/queries/0_stateless/02014_storage_merge_order_by.reference Normal file
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tests/queries/0_stateless/02014_storage_merge_order_by.sql Normal file
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DROP TABLE IF EXISTS short;
DROP TABLE IF EXISTS long;
DROP TABLE IF EXISTS merged;
CREATE TABLE short (e Int64, t DateTime ) ENGINE = MergeTree PARTITION BY e ORDER BY t;
CREATE TABLE long (e Int64, t DateTime ) ENGINE = MergeTree PARTITION BY (e, toStartOfMonth(t)) ORDER BY t;
insert into short select number % 11, toDateTime('2021-01-01 00:00:00') + number from numbers(1000);
insert into long select number % 11, toDateTime('2021-01-01 00:00:00') + number from numbers(1000);
CREATE TABLE merged as short ENGINE = Merge(currentDatabase(), 'short|long');
select sum(e) from (select * from merged order by t limit 10) SETTINGS optimize_read_in_order = 0;
select sum(e) from (select * from merged order by t limit 10) SETTINGS max_threads = 1;
select sum(e) from (select * from merged order by t limit 10) SETTINGS max_threads = 3;
select sum(e) from (select * from merged order by t limit 10) SETTINGS max_threads = 10;
select sum(e) from (select * from merged order by t limit 10) SETTINGS max_threads = 50;
DROP TABLE IF EXISTS short;
DROP TABLE IF EXISTS long;
DROP TABLE IF EXISTS merged;