1. Added support for PostgreSQL drivers.

2. Fix some bugs.

1.New version 2.0.0

2.Refactor code
3.Adapt to MySQL and SQLite databases

Attempt to fix the error.

Attempt to fix the error.

Attempt to fix the error.

Update README

Fix bugs in indexes.

Support setting index fields and JSON type fields.

Optimize the code.

Added APITest class.

Update README