Don't write to rockdb when meet empty write batch

[CalvinNeo]

Signed-off-by: CalvinNeo [email protected]

What problem does this PR solve?

Issue Number: close pingcap/tiflash#5783

Problem Summary:

There is a vulnerability in TiKV that we may meet deadlock when try to write an empty WriteBatch into RocksDB, if enable_pipelined_write = false

Aka tikv/rocksdb#312

Though we don't know exactly which codes actually bring about this vulnerability, we can still prevent writes to rocksdb and print out a log trace.

What is changed and how it works?

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

None