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
```
create table kafka
(
a UInt32,
a_str String Alias toString(a)
) engine = Kafka;
create table data
(
a UInt32;
a_str String
) engine = MergeTree
order by tuple();
create materialized view data_mv to data
(
a UInt32,
a_str String
) as
select a, a_str from kafka;
```
Alias type works as expected in comparison with MATERIALIZED/EPHEMERAL
or column with default expression.
Ref: https://github.com/ClickHouse/ClickHouse/pull/47138
Co-authored-by: Azat Khuzhin <a3at.mail@gmail.com>
https://docs.aws.amazon.com/AmazonS3/latest/userguide/UsingKMSEncryption.html
Similar to the server_side_encryption_customer_key_base64 option for
configuring SSE-C with S3, add the following settings to configure
SSE-KMS on a per-endpoint/disk basis:
- server_side_encryption_kms_key_id
- server_side_encryption_kms_encryption_context
- server_side_encryption_kms_bucket_key_enabled
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.
