AUTO_INCREMENT guarantees that it will not assign the same number twice. That's about all it is willing to guarantee.
With InnoDB, if a transaction starts, uses an auto_inc value, then rolls back, that id is lost. When you have multiple threads loading data into the same table, diff values of innodb_autoinc_lock_mode give you diff tradeoff between speed and predictability. If replication is involved, you want predictability. InnoDB and MyISAM act differently, especially after recovering from a crash. If you DELETE the _highest_ id, then restart the server, that id will be reused. (This is irritating to some people.) Otherwise, a deleted id will not be reused. There may be more. Most of those are covered here: http://mysql.rjweb.org/doc.php/ricksrots > -----Original Message----- > From: spameden [mailto:spame...@gmail.com] > Sent: Tuesday, March 12, 2013 2:46 PM > To: Rick James > Cc: mysql@lists.mysql.com > Subject: Re: auto_increment field behavior > > 2013/3/13 Rick James <rja...@yahoo-inc.com>: > > What settings? (innodb_autoinc_lock_mode comes to mind, but there > may > > be others.) > Hi, Rick. > > Many thanks for the quick answer here is my settings: > > mysql> show variables like '%inc%'; > +-----------------------------+-------+ > | Variable_name | Value | > +-----------------------------+-------+ > | auto_increment_increment | 1 | > | auto_increment_offset | 1 | > | div_precision_increment | 4 | > | innodb_autoextend_increment | 8 | > | innodb_autoinc_lock_mode | 1 | > +-----------------------------+-------+ > 5 rows in set (0.00 sec) > > > > > > It is acceptable, by the definition of AUTO_INCREMENT, for it to burn > the missing 15K ids. > > I don't get this explanation, could you please explain bit more? So > it's completely normal for AUTO_INCREMENT field to act like this? > > > > > >> -----Original Message----- > >> From: spameden [mailto:spame...@gmail.com] > >> Sent: Tuesday, March 12, 2013 2:34 PM > >> To: mysql@lists.mysql.com > >> Subject: auto_increment field behavior > >> > >> Hi, I'm running MySQL-5.5 on Ubuntu > >> > >> ~ $ mysqld -V > >> mysqld Ver 5.5.29-0ubuntu0.12.04.2 for debian-linux-gnu on x86_64 > >> ((Ubuntu)) > >> > >> Would like to know if it's normal behavior with auto_increment field > >> (tried both signed and unsigned now): > >> > >> mysql> show create table phone_codes; > >> +-------------+----------------------------------------------------- > - > >> +-------------+-- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> --+ > >> | Table | Create Table > >> > >> > >> > >> > >> > >> > >> > >> > >> | > >> +-------------+----------------------------------------------------- > - > >> +-------------+-- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> --+ > >> | phone_codes | CREATE TABLE `phone_codes` ( > >> `pc_id` int(11) NOT NULL AUTO_INCREMENT, > >> `pc_type` enum('ABC','DEF') DEFAULT NULL, > >> `pc_code` decimal(3,0) NOT NULL, > >> `pc_from` decimal(7,0) NOT NULL, > >> `pc_to` decimal(7,0) NOT NULL, > >> `pc_capacity` decimal(8,0) NOT NULL, > >> `pc_operator` varchar(255) DEFAULT NULL, > >> `pc_city` varchar(255) DEFAULT NULL, > >> `pc_region` varchar(255) DEFAULT NULL, > >> PRIMARY KEY (`pc_id`), > >> KEY `pc_code` (`pc_code`), > >> KEY `pc_code_from_to` (`pc_code`,`pc_from`,`pc_to`), > >> KEY `pc_operator` (`pc_operator`), > >> KEY `pc_city` (`pc_city`), > >> KEY `pc_region` (`pc_region`) > >> ) ENGINE=InnoDB DEFAULT CHARSET=utf8 | > >> +-------------+----------------------------------------------------- > - > >> +-------------+-- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> --+ > >> 1 row in set (0.00 sec) > >> > >> mysql> load data infile '/tmp/ABC3x' into table phone_codes fields > >> terminated by ';' enclosed by '#' lines terminated by '\r\n' > >> (pc_code,pc_from,pc_to,pc_capacity,pc_operator,pc_city,pc_region) > SET > >> pc_type='ABC'; Query OK, 17922 rows affected (4.44 sec) > >> Records: 17922 Deleted: 0 Skipped: 0 Warnings: 0 > >> > >> mysql> show create table phone_codes; > >> +-------------+----------------------------------------------------- > - > >> +-------------+-- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -----------------------+ > >> | Table | Create Table > >> > >> > >> > >> > >> > >> > >> > >> > >> | > >> +-------------+----------------------------------------------------- > - > >> +-------------+-- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -----------------------+ > >> | phone_codes | CREATE TABLE `phone_codes` ( > >> `pc_id` int(11) NOT NULL AUTO_INCREMENT, > >> `pc_type` enum('ABC','DEF') DEFAULT NULL, > >> `pc_code` decimal(3,0) NOT NULL, > >> `pc_from` decimal(7,0) NOT NULL, > >> `pc_to` decimal(7,0) NOT NULL, > >> `pc_capacity` decimal(8,0) NOT NULL, > >> `pc_operator` varchar(255) DEFAULT NULL, > >> `pc_city` varchar(255) DEFAULT NULL, > >> `pc_region` varchar(255) DEFAULT NULL, > >> PRIMARY KEY (`pc_id`), > >> KEY `pc_code` (`pc_code`), > >> KEY `pc_code_from_to` (`pc_code`,`pc_from`,`pc_to`), > >> KEY `pc_operator` (`pc_operator`), > >> KEY `pc_city` (`pc_city`), > >> KEY `pc_region` (`pc_region`) > >> ) ENGINE=InnoDB AUTO_INCREMENT=32768 DEFAULT CHARSET=utf8 | > >> +-------------+----------------------------------------------------- > - > >> +-------------+-- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -------------------------------------------------------------------- > - > >> -- > >> -----------------------+ > >> 1 row in set (0.00 sec) > >> > >> NOTE: AUTO_INCREMENT is 32768 instead of 17923 ! So next inserted > row > >> would have pc_id=32768. > >> > >> Please suggest if it's normal behavior or not. > >> > >> Many thanks. > >> > >> -- > >> MySQL General Mailing List > >> For list archives: http://lists.mysql.com/mysql > >> To unsubscribe: http://lists.mysql.com/mysql > > -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql