TiDB Limitations

This document describes the common usage limitations of TiDB, including the maximum identifier length and the maximum number of supported databases, tables, indexes, partitioned tables, and sequences.

Note

TiDB offers high compatibility with the MySQL protocol and syntax, including many MySQL limitations. For example, a single index can include a maximum of 16 columns. For more information, see MySQL Compatibility and the official MySQL documentation.

Limitations on identifier length

Identifier type	Maximum length (number of characters allowed)
Database	64
Table	64
Column	64
Index	64
View	64
Sequence	64

Limitations on the total number of databases, tables, views, and connections

Type	Maximum number
Databases	unlimited
Tables	unlimited
Views	unlimited
Connections	unlimited

Limitations on a single database

Type	Upper limit
Tables	unlimited

Limitations on a single table

Type	Upper limit (default value)
Columns	Defaults to 1017 and can be adjusted up to 4096
Indexes	Defaults to 64 and can be adjusted up to 512
Rows	unlimited
Size	unlimited
Partitions	8192

The upper limit of Columns can be modified via table-column-count-limit.
The upper limit of Indexes can be modified via index-limit.

Limitation on a single row

Type	Upper limit (default value)
Size	Defaults to 6 MiB and can be adjusted to 120 MiB

You can adjust the size limit via the txn-entry-size-limit configuration item.

Limitations on indexes

The maximum index length is 3072 bytes, equivalent to 768 characters using 4-byte UTF-8 encoding. The maximum number of columns in a single index is limited to 16.

You can adjust this limit using the max-index-length configuration item.

Limitations on data types

Type	Upper limit
CHAR	255 characters
BINARY	255 bytes
VARBINARY	65535 bytes
VARCHAR	16383 characters
TEXT	65535 bytes
BLOB	65535 bytes

Limitations on SQL statements

Type	Upper limit
The maximum number of SQL statements in a single transaction	When the optimistic transaction is used and the transaction retry is enabled, the upper limit is 5000.

You can modify the limit via the stmt-count-limit configuration item.

Limitations on TiKV version

In your cluster, if the version of the TiDB component is v6.2.0 or later, the version of TiKV must be v6.2.0 or later.