Restrictions on the use of tidb

This article will describe in detail TiDB Common usage restrictions in , Include ： Identifier length , The most supported databases 、 surface 、 Indexes 、 Partition table 、 Number of sequences, etc .

Identifier length limit

Identifier type	Maximum length （ character ）
Database	64
Table	64
Column	64
Index	64
View	64
Sequence	64

Databases、Tables、Views、Connections Total number limit

Identifier type	The maximum number
Databases	unlimited
Tables	unlimited
Views	unlimited
Connections	unlimited

Single Database The limitation of

type	Maximum restriction
Tables	unlimited

Single Table The limitation of

type	Maximum restriction （ The default value is ）
Columns	The default is 1017, Maximum adjustable to 4096
Indexs	The default is 64, Maximum adjustable to 512
Rows	unlimited
Size	unlimited
Partitions	8192

• Columns The maximum limit of can be passed through  table-column-count-limit  modify .
• Indexs The maximum limit of can be passed through  index-limit  modify .

Limit of single line

type	Maximum restriction
Size	The default is 6MB, It can be done by  txn-entry-size-limit  Configuration item adjustment

Single column restrictions

type	Maximum restriction
Size	6MB

String type restrictions

type	Maximum restriction
CHAR	256 character
BINARY	256 byte
VARBINARY	65535 byte
VARCHAR	16383 character
TEXT	6MB byte
BLOB	6MB byte

SQL Statements The limitation of

type	Maximum restriction
Maximum number of statements per transaction	When optimistic transactions are used and transaction retry is enabled , Default restrictions 5000, It can be done by  stmt-count-limit  adjustment