Refactor of error handling and badger db in-memory mode

What's Changed

• [tablesize]change the default to 2GB by @jingweicb in #438
• [types]remove two fields in preprocess request by @jingweicb in #439
• replace a comment by @jingweicb in #445
• Error handling refactor by @GeekArthur in #446

Full Changelog: v0.8.0...v0.8.1