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.