TiDB Lightning Overview
- TiDB Lightning architecture

TiDB Lightning Overview

TiDB Lightning is a tool used for importing data at TB scale to TiDB clusters. It is often used for initial data import to TiDB clusters.

TiDB Lightning supports the following file formats:

Files exported by Dumpling
CSV files
Apache Parquet files generated by Amazon Aurora

TiDB Lightning can read data from the following sources:

TiDB Lightning architecture

TiDB Lightning supports two import modes, configured by backend. The import mode determines the way data is imported into TiDB.

Physical Import Mode: TiDB Lightning first encodes data into key-value pairs and stores them in a local temporary directory, then uploads these key-value pairs to each TiKV node, and finally calls the TiKV Ingest interface to insert data into TiKV’s RocksDB. If you need to perform initial import, consider the physical import mode, which has higher import speed. The backend for the physical import mode is local.
Logical Import Mode: TiDB Lightning first encodes the data into SQL statements and then runs these SQL statements directly for data import. If the cluster to be imported is in production, or if the target table to be imported already contains data, use the logical import mode. The backend for the logical import mode is tidb.

Import mode	Physical Import Mode	Logical Import Mode
Backend	`local`	`tidb`
Speed	Fast (100~500 GiB/hour)	Low (10~50 GiB/hour)
Resource consumption	High	Low
Network bandwidth consumption	High	Low
ACID compliance during import	No	Yes
Target tables	Must be empty	Can contain data
TiDB cluster version	>= 4.0.0	All
Whether the TiDB cluster can provide service during import	Limited service	Yes

Note

The preceding performance data is used to compare the import performance difference between the two modes. The actual import speed is affected by various factors such as hardware configuration, table schema, and the number of indexes.