Specified key was too long; max key length is 1000 bytes in mysql 5.6

one of the application server is internally creating the database on my mysql but when ever the following create table command gets executed

CREATE TABLE ofRoster (   

    rosterID              BIGINT          NOT NULL,   
    username              VARCHAR(64)     NOT NULL,   
    jid                   VARCHAR(1024)   NOT NULL,   
    sub                   TINYINT         NOT NULL,   

    ask                   TINYINT         NOT NULL,   
    recv                  TINYINT         NOT NULL,   
    nick                  VARCHAR(255),   
    PRIMARY KEY (rosterID),   
    INDEX ofRoster_unameid_idx (username),   
    INDEX ofRoster_jid_idx (jid) 

 )

i am getting following error

ERROR 1071 (42000): Specified key was too long; max key length is 1000 bytes

i have set my default engine to MyISAM because i was getting following error in InnoDB

specified key was too long max key length is 767 bytes

my current engines are as follows

```
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| Engine | Support | Comment | Transactions | XA | Savepoints |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| FEDERATED | NO | Federated MySQL storage engine | NULL | NULL | NULL |
| MRG_MYISAM | YES | Collection of identical MyISAM tables | NO | NO | NO |
| MyISAM | DEFAULT | MyISAM storage engine | NO | NO | NO |
| BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) | NO | NO | NO |
| CSV | YES | CSV storage engine

You can increase the maximum InnoDB index prefix size in MySQL 5.6 to 3072 bytes by setting innodb_large_prefix to ON along with other settings that you'll also need in order to enable that one, discussed here:

http://dev.mysql.com/doc/refman/5.6/en/innodb-parameters.html#sysvar_innodb_large_prefix

These changes should allow these indexes to be valid for InnoDB tables.

With a character set of (I assume) utf8, a VARCHAR(1024) would need 1024 x 3 = 3072 bytes for its index.

Updates:

I incorrectly showed the value of the variable as Yes when it should have been ON.

But also:


I think it needs 3072+2 – ypercube

When I thought about this, it sounded correct, because 1 byte is needed to store the size of the value when the value is 255 bytes or less, and 2 bytes are needed otherwise.

However, testing reveals that this isn't the case, in this case -- InnoDB using the COMPRESSED row format from Barracuda can actually index the full size of a VARCHAR(1024)... so either they've documented it strangely or the COMPRESSED row format stores the length out-of-band along with another block of metadata, so it doesn't count in the total bytes in this format.

COMPRESSED doesn't truncate the index into a prefix index and throw a warning until you go to VARCHAR(1025).

+-------+------+----------------------------------------------------------+
| Level | Code | Message                                                  |
+-------+------+----------------------------------------------------------+
| Error | 1071 | Specified key was too long; max key length is 3072 bytes |
+-------+------+----------------------------------------------------------+

It's nice the way it throws a warning instead of throwing an error, but that doesn't help us here because this still requires the explicit ROW_FORMAT declaration to trigger this behavior.

So, my initial answer is still wrong, because you have to explicitly add ROW_FORMAT=COMPRESSED to the end of the table definition. Otherwise you still get the same old error.

Actually, you get two different errors in 5.6.10. If you try to create a table with a fully-indexed VARCHAR(1024) you get this:

ERROR 1709 (HY000): Index column size too large. The maximum column size is 767 bytes.

...but if you try with a fully-indexed VARCHAR(1025) you get this:

ERROR 1071 (42000): Specified key was too long; max key length is 3072 bytes

That's sloppy code but the bottom line is that my answer doesn't actually fix this problem.

I don't see a way to use ROW_FORMAT=COMPRESSED by default, nor does it seem like a good idea if it were possible, and I'm inclined to suggest that the answer is...

...there's not a readily available workaround here. My other thought was "character sets" but the difference between latin1 and utf8 still isn't sufficient to explain 1,024 vs 1000 or 767. I'll happily get behind a better idea but at the moment, I can't think of a version of MySQL Server that this code would work properly on.

StackExchange Database Administrators Q#49913, answer score: 4