After #36425 there was a lot of confusions/problems with configuring pools - when the message was confusing, and settings need to be ajusted in several places.
See some examples in #44251, #43351, #47900, #46515.
The commit includes the following changes:
1) Introduced a unified mechanism for reading pool sizes from the configuration file(s). Previously, pool sizes were read from the Context.cpp with fallbacks to profiles, whereas main_config_reloader in Server.cpp read them directly without fallbacks.
2) Corrected the data type for background_merges_mutations_concurrency_ratio. It should be float instead of int.
3) Refactored the default values for settings. Previously, they were defined in multiple places throughout the codebase, but they are now defined in one place (or two, to be exact: Settings.h and ServerSettings.h).
4) Improved documentation, including the correct message in system.settings.
Additionally make the code more conform with #46550.
There are lots of thread pools and simple local-vs-global is not enough
already, it is good to know which one in particular uses threads.
Signed-off-by: Azat Khuzhin <a.khuzhin@semrush.com>
CI reports [1]:
2023.03.14 00:29:07.031349 [ 166170 ] {110f8654-7d7d-4b47-b6b0-3ce83414a80f} <Error> ReadWriteBufferFromHTTP: HTTP request to `http://127.0.0.1:9018/columns_info?use_connection_pooling=1&version=1&connection_string=DSN%3D%7BClickHouse%20DSN%20%28ANSI%29%7D&schema=test_15&table=t&external_table_functions_use_nulls=1` failed at try 1/1 with bytes read: 0/unknown. Error: DB::HTTPException: Received error from remote server /columns_info?use_connection_pooling=1&version=1&connection_string=DSN%3D%7BClickHouse%20DSN%20%28ANSI%29%7D&schema=test_15&table=t&external_table_functions_use_nulls=1. HTTP status code: 500 Internal Server Error, body: Error getting columns from ODBC 'Code: 49. DB::Exception: Columns definition was not returned. (LOGICAL_ERROR) (version 23.2.4.12 (official build))'
[1]: https://s3.amazonaws.com/clickhouse-test-reports/47541/3d247b8635da44bccfdeb5fcd53be7130b8d0a32/upgrade_check__msan_.html
Here the problem is that system.columns has cached value for number of
total table to iterate, and so it can skip something.
But anyway, this should be LOGICAL_ERROR, since ODBC bridge does two
queries:
- to system.tables and
- to system.columns
And if between this two queries the table will be removed, them there
will be no columns
Signed-off-by: Azat Khuzhin <a.khuzhin@semrush.com>
