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[Maria-developers] How to change max key length for MyISAM?

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Witold Filipczyk

14 Jan 2021 14 Jan '21

7:24 p.m.

Sorry, for private question, but I did not know where to ask. mariadb-10.3.27. I changed in include/myisam.h: #define MI_MAX_KEY_LENGTH 3072 /* Max length in bytes */ but, it did not help, still this ERROR 1071 (42000): Specified key was too long; max key length is 1000 bytes. What more to change to get key length 3072 for MyISAM tables? And what can be negative impact of such a change? Witold Filipczyk

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Sergei Golubchik

14 Jan 14 Jan

8:25 p.m.

Hi, Witold! On Jan 14, Witold Filipczyk wrote:

Sorry, for private question, but I did not know where to ask. mariadb-10.3.27.

I changed in include/myisam.h:

#define MI_MAX_KEY_LENGTH 3072 /* Max length in bytes */

but, it did not help, still this ERROR 1071 (42000): Specified key was too long; max key length is 1000 bytes.

What more to change to get key length 3072 for MyISAM tables?

Change HA_MAX_KEY_LENGTH. MI_MAX_KEY_LENGTH is only used for temporary tables.

And what can be negative impact of such a change?

More memory on the stack, so if you have a table with lots and lots of rows, searching for long keys is more likely to cause overflow the stack. Might be slower, perhaps, as it'll need to copy more data. It's all "might", may be there will be no negative impact at all. Why do you want to increase the max key length? Regards, Sergei VP of MariaDB Server Engineering and security@mariadb.org

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Witold Filipczyk

8:43 p.m.

Dnia Thu, Jan 14, 2021 at 08:25:42PM +0100, Sergei Golubchik napisał(a):

Hi, Witold!

On Jan 14, Witold Filipczyk wrote:

...
Sorry, for private question, but I did not know where to ask. mariadb-10.3.27.

I changed in include/myisam.h:

#define MI_MAX_KEY_LENGTH 3072 /* Max length in bytes */

but, it did not help, still this ERROR 1071 (42000): Specified key was too long; max key length is 1000 bytes.

What more to change to get key length 3072 for MyISAM tables?

Change HA_MAX_KEY_LENGTH. MI_MAX_KEY_LENGTH is only used for temporary tables.

I'll try. Thanks!

...
And what can be negative impact of such a change?

More memory on the stack, so if you have a table with lots and lots of rows, searching for long keys is more likely to cause overflow the stack. Might be slower, perhaps, as it'll need to copy more data. It's all "might", may be there will be no negative impact at all.

Why do you want to increase the max key length?

I like mysqlhotcopy as backup tool, but new soft requires big key.

Regards, Sergei VP of MariaDB Server Engineering and security@mariadb.org

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Sergei Golubchik

8:52 p.m.

Hi, Witold! On Jan 14, Witold Filipczyk wrote:

...
Why do you want to increase the max key length?

I like mysqlhotcopy as backup tool, but new soft requires big key.

Yes, that's what I was asking. What does it require, can you show an example of a table definition? I mean, a non-unique key doesn't have to be that long. If it's smaller, it'll still help to narrow the search to all rows with the same 1000-byte prefix, and then just compare them all with the exact 3K value. So 1K-key will still help even if values are 3K (except when all your values have exactly the same 1K prefix, but it's not a very realistic scenario). But with 1K keys you'll fit 3 times more keys per index page, you'll have less disk IO, and less tree levels to search. You would really need 3K, if you have 3K UNIQUE key, for UNIQUE 3k contraints. Using 1K keys would change the semantics, values won't necessarily be unique anymore. But since 10.4 MariaDB supports unique constraints of arbitrary length. So, again, you should not need to increase max key length for that (except that you're on 10.3 now). Regards, Sergei VP of MariaDB Server Engineering and security@mariadb.org

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Witold Filipczyk

9:39 p.m.

Dnia Thu, Jan 14, 2021 at 08:52:14PM +0100, Sergei Golubchik napisał(a):

Hi, Witold!

On Jan 14, Witold Filipczyk wrote:

...
...
Why do you want to increase the max key length?

I like mysqlhotcopy as backup tool, but new soft requires big key.

Yes, that's what I was asking. What does it require, can you show an example of a table definition?

I mean, a non-unique key doesn't have to be that long. If it's smaller, it'll still help to narrow the search to all rows with the same 1000-byte prefix, and then just compare them all with the exact 3K value. So 1K-key will still help even if values are 3K (except when all your values have exactly the same 1K prefix, but it's not a very realistic scenario). But with 1K keys you'll fit 3 times more keys per index page, you'll have less disk IO, and less tree levels to search.

You would really need 3K, if you have 3K UNIQUE key, for UNIQUE 3k contraints. Using 1K keys would change the semantics, values won't necessarily be unique anymore. But since 10.4 MariaDB supports unique constraints of arbitrary length. So, again, you should not need to increase max key length for that (except that you're on 10.3 now).

I'm trying to install prestashop-1.7.7.1 on MyISAM.

Regards, Sergei VP of MariaDB Server Engineering and security@mariadb.org

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Reindl Harald

9:45 p.m.

Am 14.01.21 um 21:39 schrieb Witold Filipczyk:

Dnia Thu, Jan 14, 2021 at 08:52:14PM +0100, Sergei Golubchik napisał(a):

...
Hi, Witold!

On Jan 14, Witold Filipczyk wrote:

...
...
Why do you want to increase the max key length?

I like mysqlhotcopy as backup tool, but new soft requires big key.

Yes, that's what I was asking. What does it require, can you show an example of a table definition?

I mean, a non-unique key doesn't have to be that long. If it's smaller, it'll still help to narrow the search to all rows with the same 1000-byte prefix, and then just compare them all with the exact 3K value. So 1K-key will still help even if values are 3K (except when all your values have exactly the same 1K prefix, but it's not a very realistic scenario). But with 1K keys you'll fit 3 times more keys per index page, you'll have less disk IO, and less tree levels to search.

You would really need 3K, if you have 3K UNIQUE key, for UNIQUE 3k contraints. Using 1K keys would change the semantics, values won't necessarily be unique anymore. But since 10.4 MariaDB supports unique constraints of arbitrary length. So, again, you should not need to increase max key length for that (except that you're on 10.3 now).

I'm trying to install prestashop-1.7.7.1 on MyISAM

and why does that piece of software don't work with sensible defaults and force you too pacth source code and recompile your database server in a way nobody but you is running? this is asking for troubles and until someone can prove a *real* benefit i call it bullshit and won#t install "prestashop-1.7.7.1 on MyISAM" the other possibilty is that it's designed to work with innoDB and *not* MyISAM which means: just don't enforce MyISAM, key sizes are your smallest problems in reality

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Luuk

15 Jan 15 Jan

9:01 a.m.

On 14-1-2021 21:45, Reindl Harald wrote:

Am 14.01.21 um 21:39 schrieb Witold Filipczyk:

...
Dnia Thu, Jan 14, 2021 at 08:52:14PM +0100, Sergei Golubchik napisał(a):

...
Hi, Witold!

On Jan 14, Witold Filipczyk wrote:

...
...
Why do you want to increase the max key length?

I like mysqlhotcopy as backup tool, but new soft requires big key.

Yes, that's what I was asking. What does it require, can you show an example of a table definition?

I mean, a non-unique key doesn't have to be that long. If it's smaller, it'll still help to narrow the search to all rows with the same 1000-byte prefix, and then just compare them all with the exact 3K value. So 1K-key will still help even if values are 3K (except when all your values have exactly the same 1K prefix, but it's not a very realistic scenario). But with 1K keys you'll fit 3 times more keys per index page, you'll have less disk IO, and less tree levels to search.

You would really need 3K, if you have 3K UNIQUE key, for UNIQUE 3k contraints. Using 1K keys would change the semantics, values won't necessarily be unique anymore. But since 10.4 MariaDB supports unique constraints of arbitrary length. So, again, you should not need to increase max key length for that (except that you're on 10.3 now).

I'm trying to install prestashop-1.7.7.1 on MyISAM

and why does that piece of software don't work with sensible defaults and force you too pacth source code and recompile your database server in a way nobody but you is running?

this is asking for troubles and until someone can prove a *real* benefit i call it bullshit and won#t install "prestashop-1.7.7.1 on MyISAM"

the other possibilty is that it's designed to work with innoDB and *not* MyISAM which means: just don't enforce MyISAM, key sizes are your smallest problems in reality

Error 1071 at Installation Prestashop 1.7.11 - Installing PrestaShop for the first time - PrestaShop Forums https://www.prestashop.com/forums/topic/605679-error-1071-at-installation-pr... [quoot] April 18, 2017 Q: i have a problem. i cant install the prestashop 1.7.11 because i get this Error Message: "SQLSTATE[42000]: Syntax error or access violation: 1071 Specified key was too long; max key length is 1000 bytes".How can i fix this problem. i have tried everything:( A: It is a MySQL issue. http://stackoverflow.com/questions/8746207/1071-specified-key-was-too-long-m... http://stackoverflow.com/questions/8746207/1071-specified-key-was-too-long-m... [/quoot] 😵😖🥱🥱😉

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Reindl Harald

10:09 a.m.

Am 15.01.21 um 09:01 schrieb Luuk:

On 14-1-2021 21:45, Reindl Harald wrote:

...
...
I'm trying to install prestashop-1.7.7.1 on MyISAM

and why does that piece of software don't work with sensible defaults and force you too pacth source code and recompile your database server in a way nobody but you is running?

this is asking for troubles and until someone can prove a *real* benefit i call it bullshit and won't install "prestashop-1.7.7.1 on MyISAM"

the other possibilty is that it's designed to work with innoDB and *not* MyISAM which means: just don't enforce MyISAM, key sizes are your smallest problems in reality

A: It is a MySQL issue. http://stackoverflow.com/questions/8746207/1071-specified-key-was-too-long-m...

as expected DO NOT INSTALL IT ON MYISAM jesus christ ENGINE=InnoDB and no it's not a mysql issue when a software is written in a way than even the installer dies CREATE TABLE IF NOT EXISTS `pds_core_menu_items` ( `menu_id` varchar(32) NOT NULL, `parent_menu_id` int(32) unsigned DEFAULT NULL, `menu_name` varchar(255) DEFAULT NULL, `menu_link` varchar(255) DEFAULT NULL, `plugin` varchar(255) DEFAULT NULL, `menu_type` int(1) DEFAULT NULL, `extend` varchar(255) DEFAULT NULL, `new_window` int(1) DEFAULT NULL, `rank` int(100) DEFAULT NULL, `hide` int(1) DEFAULT NULL, `template_id` int(32) unsigned DEFAULT NULL, `alias` varchar(255) DEFAULT NULL, `layout` varchar(255) DEFAULT NULL, PRIMARY KEY (`menu_id`), KEY `index` (`parent_menu_id`,`menu_link`,`plugin`,`alias`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;

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jocelyn fournier

10:57 a.m.

Just FYI, I confirm Prestashop (at least since 1.6.1.x) is designed to work much better on InnoDB than MyISAM BR, Jocelyn Fournier

Le 15 janv. 2021 à 10:09, Reindl Harald a écrit :

Am 15.01.21 um 09:01 schrieb Luuk:

...
On 14-1-2021 21:45, Reindl Harald wrote:

...
...
I'm trying to install prestashop-1.7.7.1 on MyISAM

and why does that piece of software don't work with sensible defaults and force you too pacth source code and recompile your database server in a way nobody but you is running?

this is asking for troubles and until someone can prove a *real* benefit i call it bullshit and won't install "prestashop-1.7.7.1 on MyISAM"

the other possibilty is that it's designed to work with innoDB and *not* MyISAM which means: just don't enforce MyISAM, key sizes are your smallest problems in reality A: It is a MySQL issue. http://stackoverflow.com/questions/8746207/1071-specified-key-was-too-long-m...

as expected DO NOT INSTALL IT ON MYISAM jesus christ ENGINE=InnoDB

and no it's not a mysql issue when a software is written in a way than even the installer dies

CREATE TABLE IF NOT EXISTS `pds_core_menu_items` ( `menu_id` varchar(32) NOT NULL, `parent_menu_id` int(32) unsigned DEFAULT NULL, `menu_name` varchar(255) DEFAULT NULL, `menu_link` varchar(255) DEFAULT NULL, `plugin` varchar(255) DEFAULT NULL, `menu_type` int(1) DEFAULT NULL, `extend` varchar(255) DEFAULT NULL, `new_window` int(1) DEFAULT NULL, `rank` int(100) DEFAULT NULL, `hide` int(1) DEFAULT NULL, `template_id` int(32) unsigned DEFAULT NULL, `alias` varchar(255) DEFAULT NULL, `layout` varchar(255) DEFAULT NULL, PRIMARY KEY (`menu_id`), KEY `index` (`parent_menu_id`,`menu_link`,`plugin`,`alias`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;

_______________________________________________ Mailing list: https://launchpad.net/~maria-developers Post to : maria-developers@lists.launchpad.net Unsubscribe : https://launchpad.net/~maria-developers More help : https://help.launchpad.net/ListHelp

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jocelyn fournier
Luuk
Reindl Harald
Sergei Golubchik
Witold Filipczyk