1. Disable the MySQL client and LZO library by default when building the Doris.
MySQL client library is used for MySQL external table feature.
This feature will be replaced by the new ODBC external table soon.
LZO library is used to compress/decompress data of some old data format of Doris,
which is no longer used anymore.
2. Add missing license to some files.
3. For all non-Apache-License code, all are explained in NOTICE file and the corresponding license is declared.
4. Remove the js source code from webroot, it will be downloaded as thirdparty
Its time to enable some features by default.
1. Enable FE plugins by setting `plugin_enable=true`
2. Enable dynamic partition by setting `dynamic_partition_enable=true`
3. Enable nio mysql server by setting `mysql_service_nio_enabled=true`
Also modify installation doc, add download link of MySQL client.
When starting FE with `start_fe.sh --helper xxx` command, do not allow to
point helper to FE itself. Because this is meaningless and may cause some
confusing problemes.
