MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6
This section describes limits for InnoDB
tables, indexes, tablespaces, and other aspects of the
InnoDB
storage engine.
A table can contain a maximum of 1017 columns (raised in MySQL 5.6.9 from the earlier limit of 1000). Virtual generated columns are included in this limit.
A table can contain a maximum of 64 secondary indexes.
If innodb_large_prefix
is
enabled (the default), the index key prefix limit is 3072
bytes for InnoDB
tables that use the
DYNAMIC
or
COMPRESSED
row format. If
innodb_large_prefix
is
disabled, the index key prefix limit is 767 bytes for tables
of any row format.
innodb_large_prefix
is
deprecated; expect it to be removed in a future MySQL release.
innodb_large_prefix
was
introduced in MySQL 5.5 to disable large index key prefixes
for compatibility with earlier versions of
InnoDB
that do not support large index key
prefixes.
The index key prefix length limit is 767 bytes for
InnoDB
tables that use the
REDUNDANT
or
COMPACT
row format. For example, you might hit this limit with a
column prefix index
of more than 255 characters on a TEXT
or
VARCHAR
column, assuming a
utf8mb3
character set and the maximum of 3
bytes for each character.
Attempting to use an index key prefix length that exceeds the
limit returns an error. To avoid such errors in replication
configurations, avoid enabling
innodb_large_prefix
on the
source if it cannot also be enabled on replicas.
If you reduce the InnoDB
page size to 8KB or 4KB
by specifying the
innodb_page_size
option when
creating the MySQL instance, the maximum length of the index
key is lowered proportionally, based on the limit of 3072
bytes for a 16KB page size. That is, the maximum index key
length is 1536 bytes when the page size is 8KB, and 768 bytes
when the page size is 4KB.
The limits that apply to index key prefixes also apply to full-column index keys.
A maximum of 16 columns is permitted for multicolumn indexes. Exceeding the limit returns an error.
ERROR 1070 (42000): Too many key parts specified; max 16 parts allowed
The maximum row size, excluding any variable-length columns
that are stored off-page, is slightly less than half of a page
for 4KB, 8KB, 16KB, and 32KB page sizes. For example, the
maximum row size for the default
innodb_page_size
of 16KB is
about 8000 bytes. However, for an InnoDB
page size of 64KB, the maximum row size is approximately 16000
bytes. LONGBLOB
and
LONGTEXT
columns must be less than 4GB, and the total row size,
including BLOB
and
TEXT
columns, must be less than
4GB.
If a row is less than half a page long, all of it is stored locally within the page. If it exceeds half a page, variable-length columns are chosen for external off-page storage until the row fits within half a page, as described in Section 14.12.2, “File Space Management”.
Although InnoDB
supports row sizes larger
than 65,535 bytes internally, MySQL itself imposes a row-size
limit of 65,535 for the combined size of all columns. See
Section 8.4.7, “Limits on Table Column Count and Row Size”.
On some older operating systems, files must be less than 2GB.
This is not an InnoDB
limitation. If you
require a large system tablespace, configure it using several
smaller data files rather than one large data file, or
distribute table data across file-per-table and general
tablespace data files.
The combined maximum size for InnoDB
log
files is 512GB.
The minimum tablespace size is slightly larger than 10MB. The
maximum tablespace size depends on the
InnoDB
page size.
Table 14.25 InnoDB Maximum Tablespace Size
InnoDB Page Size | Maximum Tablespace Size |
---|---|
4KB | 16TB |
8KB | 32TB |
16KB | 64TB |
32KB | 128TB |
64KB | 256TB |
The maximum tablespace size is also the maximum size for a table.
Tablespace files cannot exceed 4GB on Windows 32-bit systems (Bug #80149).
The path of a tablespace file, including the file name, cannot
exceed the MAX_PATH
limit on Windows. Prior
to Windows 10, the MAX_PATH
limit is 260
characters. As of Windows 10, version 1607,
MAX_PATH
limitations are removed from
common Win32 file and directory functions, but you must enable
the new behavior.
ROW_FORMAT=COMPRESSED
in the
Barracuda file format
assumes that the page size is at most 16KB and uses 14-bit
pointers.
For limits associated with concurrent read-write transactions, see Section 14.6.7, “Undo Logs”.