$ clickhouse-benchmark -i 10000 -d 0 --parallelize_output_from_storages=0 -q "select * from values('foo')"
Loaded 1 queries.
Queries executed: 10000.
localhost:9000, queries 10000, QPS: 2800.490, RPS: 2800.490, MiB/s: 0.032, result RPS: 2800.490, result MiB/s: 0.032.
0.000% 0.000 sec.
10.000% 0.000 sec.
20.000% 0.000 sec.
30.000% 0.000 sec.
40.000% 0.000 sec.
50.000% 0.000 sec.
60.000% 0.000 sec.
70.000% 0.000 sec.
80.000% 0.000 sec.
90.000% 0.000 sec.
95.000% 0.000 sec.
99.000% 0.001 sec.
99.900% 0.001 sec.
99.990% 0.001 sec.
$ clickhouse-benchmark -i 10000 -d 0 --parallelize_output_from_storages=1 -q "select * from values('foo')"
Loaded 1 queries.
Queries executed: 10000.
localhost:9000, queries 10000, QPS: 1259.805, RPS: 1259.805, MiB/s: 0.014, result RPS: 1259.805, result MiB/s: 0.014.
0.000% 0.001 sec.
10.000% 0.001 sec.
20.000% 0.001 sec.
30.000% 0.001 sec.
40.000% 0.001 sec.
50.000% 0.001 sec.
60.000% 0.001 sec.
70.000% 0.001 sec.
80.000% 0.001 sec.
90.000% 0.001 sec.
95.000% 0.001 sec.
99.000% 0.001 sec.
99.900% 0.001 sec.
99.990% 0.003 sec.
Signed-off-by: Azat Khuzhin <a.khuzhin@semrush.com>
Adding more processors for parallelize_output_from_storages is not a
costless operation (I've experienced some issues in production because
of this), and it is not easy to fix in a normal way, so let's disable it
for now.
Before this patch:
- INSERT INTO input SELECT * FROM numbers(10e6) SETTINGS parallelize_output_from_storages=1, min_insert_block_size_rows=1000
0 rows in set. Elapsed: 3.648 sec. Processed 20.00 million rows, 120.00 MB (5.48 million rows/s., 32.90 MB/s.)
- INSERT INTO input SELECT * FROM numbers(10e6) SETTINGS parallelize_output_from_storages=0, min_insert_block_size_rows=1000
0 rows in set. Elapsed: 1.851 sec. Processed 20.00 million rows, 120.00 MB (10.80 million rows/s., 64.82 MB/s.)
Signed-off-by: Azat Khuzhin <a.khuzhin@semrush.com>
Updated PostgreSQL documentation to better show example of using PostgreSQL() table engine for SELECT and INSERT, vs. copying data via postgresql() table function for copying data into ClickHouse
Empty table overrides are formatted without any parenthesises,
but they are required by a parser,
and it is not possible to parse empty table overrides without it.
:) CREATE DATABASE db ... TABLE OVERRIDE t1()
CREATE DATABASE db
...
TABLE OVERRIDE `t1`
This query will be saved to metadata and ClickHouse will not be able to start up, since
table overrides require ().
