1. Add new setting for Kafka engine, named kafka_thread_per_consumer which default value is false. 2. Create separate thread pool for Kafka engine.

disallow empty time_zone argument in toStartOf* type of functions

Add retries to integration test_host_ip_change

Fix flaky test 01280_ttl_where_group_by

Stop query execution if exception happened in PipelineExecutor itself.

Add explicit main_configs, user_configs and dictionaries in integration tests

Apply TTL if it's not calculated for part

Support MySQL handler 'set @@xx' settting

* created program in utils

* reset test

* removed additional printings

* refactoring

* fix float generator, fix build

* add readme

* refactor readme

* fixed random int func

* clang format

* fix build

* fix build

* fix PVS, uncrustify

* newline at end of file

* refactor string_type func

* restyle func maps

* support IN operation

* support multiquery

* fix style

* change rand to pcg64

* fix array generation

* fix build

* better

* subqueries

* style

* better

* delete samples.sql
Co-authored-by: NRoman Ilgovskiy <ilgovskiy@yandex-team.ru>

Fix mysql replication GTID event dump format

Wait for clickhouse-server to start in stateful tests

Fix select parts for merge

Check for array size overflow in topK

Website fix bugs

Provide a way to quickly test the website

Remove redundant conditions

Simplify mutations tests

Add missed #include <atomic>

Proxy restart/start/stop/reload of SysVinit to systemd (if it is used)

Optimize queries with LIMIT/LIMIT BY/ORDER BY for distributed with GROUP BY sharding_key