Bug#19025 4.1 mysqldump doesn't correctly dump "auto_increment = [int]"

mysqldump / SHOW CREATE TABLE will show the NEXT available value for
the PK, rather than the *first* one that was available (that named in
the original CREATE TABLE ... AUTO_INCREMENT = ... statement).

This should produce correct and robust behaviour for the obvious use
cases -- when no data were inserted, then we'll produce a statement
featuring the same value the original CREATE TABLE had; if we dump
with values, INSERTing the values on the target machine should set the
correct next_ID anyway (and if not, we'll still have our AUTO_INCREMENT =
... to do that). Lastly, just the CREATE statement (with no data) for
a table that saw inserts would still result in a table that new values
could safely be inserted to).

There seems to be no robust way however to see whether the next_ID
field is > 1 because it was set to something else with CREATE TABLE
... AUTO_INCREMENT = ..., or because there is an AUTO_INCREMENT column
in  the table (but no initial value was set with AUTO_INCREMENT = ...)
and then one or more rows were INSERTed, counting up next_ID. This
means that in both cases, we'll generate an AUTO_INCREMENT =
... clause in SHOW CREATE TABLE / mysqldump.  As we also show info on,
say, charsets even if the user did not explicitly give that info in
their own CREATE TABLE, this shouldn't be an issue.

As per above, the next_ID will be affected by any INSERTs that have
taken place, though.  This /should/ result in correct and robust
behaviour, but it may look non-intuitive to some users if they CREATE
TABLE ... AUTO_INCREMENT = 1000 and later (after some INSERTs) have
SHOW CREATE TABLE give them a different value (say, CREATE TABLE
... AUTO_INCREMENT = 1006), so the docs should possibly feature a
caveat to that effect.

It's not very intuitive the way it works now (with the fix), but it's
*correct*.  We're not storing the original value anyway, if we wanted
that, we'd have to change on-disk representation?

If we do dump/load cycles with empty DBs, nothing will change.  This
changeset includes an additional test case that proves that tables
with rows will create the same next_ID for AUTO_INCREMENT = ... across
dump/restore cycles.

Confirmed by support as likely solution for client's problem.

mysql-test/r/auto_increment.result

@@ -355,3 +355,27 @@ CHECK TABLE t1;
 Table	Op	Msg_type	Msg_text
 test.t1	check	status	OK
 DROP TABLE IF EXISTS t1;
+CREATE TABLE `t1` (
+t1_name VARCHAR(255) DEFAULT NULL,
+t1_id INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
+KEY (t1_name),
+PRIMARY KEY (t1_id)
+) AUTO_INCREMENT = 1000;
+INSERT INTO t1 (t1_name) VALUES('MySQL');
+INSERT INTO t1 (t1_name) VALUES('MySQL');
+INSERT INTO t1 (t1_name) VALUES('MySQL');
+SELECT * from t1;
+t1_name	t1_id
+MySQL	1000
+MySQL	1001
+MySQL	1002
+SHOW CREATE TABLE `t1`;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `t1_name` varchar(255) default NULL,
+  `t1_id` int(10) unsigned NOT NULL auto_increment,
+  PRIMARY KEY  (`t1_id`),
+  KEY `t1_name` (`t1_name`)
+) ENGINE=MyISAM AUTO_INCREMENT=1003 DEFAULT CHARSET=latin1
+DROP TABLE `t1`;
+End of 4.1 tests

mysql-test/r/gis-rtree.result

@@ -294,7 +294,7 @@ t2	CREATE TABLE `t2` (
   `g` geometry NOT NULL default '',
   PRIMARY KEY  (`fid`),
   SPATIAL KEY `g` (`g`(32))
-) ENGINE=MyISAM DEFAULT CHARSET=latin1
+) ENGINE=MyISAM AUTO_INCREMENT=101 DEFAULT CHARSET=latin1
 SELECT count(*) FROM t2;
 count(*)
 100

mysql-test/r/mysqldump.result

@@ -1503,3 +1503,41 @@ select * from t1;
 a	b
 Osnabrck	Kln
 drop table t1;
+create table `t1` (
+t1_name varchar(255) default null,
+t1_id int(10) unsigned not null auto_increment,
+key (t1_name),
+primary key (t1_id)
+) auto_increment = 1000 default charset=latin1;
+insert into t1 (t1_name) values('bla');
+insert into t1 (t1_name) values('bla');
+insert into t1 (t1_name) values('bla');
+select * from t1;
+t1_name	t1_id
+bla	1000
+bla	1001
+bla	1002
+show create table `t1`;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `t1_name` varchar(255) default NULL,
+  `t1_id` int(10) unsigned NOT NULL auto_increment,
+  PRIMARY KEY  (`t1_id`),
+  KEY `t1_name` (`t1_name`)
+) ENGINE=MyISAM AUTO_INCREMENT=1003 DEFAULT CHARSET=latin1
+DROP TABLE `t1`;
+select * from t1;
+t1_name	t1_id
+bla	1000
+bla	1001
+bla	1002
+show create table `t1`;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `t1_name` varchar(255) default NULL,
+  `t1_id` int(10) unsigned NOT NULL auto_increment,
+  PRIMARY KEY  (`t1_id`),
+  KEY `t1_name` (`t1_name`)
+) ENGINE=MyISAM AUTO_INCREMENT=1003 DEFAULT CHARSET=latin1
+drop table `t1`;
+End of 4.1 tests

mysql-test/r/symlink.result

@@ -40,7 +40,7 @@ t9	CREATE TABLE `t9` (
   `b` char(16) NOT NULL default '',
   `c` int(11) NOT NULL default '0',
   PRIMARY KEY  (`a`)
-) ENGINE=MyISAM DEFAULT CHARSET=latin1 DATA DIRECTORY='TEST_DIR/var/tmp/' INDEX DIRECTORY='TEST_DIR/var/run/'
+) ENGINE=MyISAM AUTO_INCREMENT=16725 DEFAULT CHARSET=latin1 DATA DIRECTORY='TEST_DIR/var/tmp/' INDEX DIRECTORY='TEST_DIR/var/run/'
 alter table t9 rename t8, add column d int not null;
 alter table t8 rename t7;
 rename table t7 to t9;
@@ -62,7 +62,7 @@ t9	CREATE TABLE `t9` (
   `c` int(11) NOT NULL default '0',
   `d` int(11) NOT NULL default '0',
   PRIMARY KEY  (`a`)
-) ENGINE=MyISAM DEFAULT CHARSET=latin1 DATA DIRECTORY='TEST_DIR/var/tmp/' INDEX DIRECTORY='TEST_DIR/var/run/'
+) ENGINE=MyISAM AUTO_INCREMENT=16725 DEFAULT CHARSET=latin1 DATA DIRECTORY='TEST_DIR/var/tmp/' INDEX DIRECTORY='TEST_DIR/var/run/'
 drop database mysqltest;
 create table t1 (a int not null) engine=myisam;
 show create table t1;

mysql-test/t/auto_increment.test

@@ -219,4 +219,23 @@ INSERT INTO t1 (b) VALUES ('bbbb');
 CHECK TABLE t1;
 DROP TABLE IF EXISTS t1;
 
-# End of 4.1 tests
+# BUG #19025:
+
+CREATE TABLE `t1` (
+    t1_name VARCHAR(255) DEFAULT NULL,
+    t1_id INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
+    KEY (t1_name),
+    PRIMARY KEY (t1_id)
+) AUTO_INCREMENT = 1000;
+
+INSERT INTO t1 (t1_name) VALUES('MySQL');
+INSERT INTO t1 (t1_name) VALUES('MySQL');
+INSERT INTO t1 (t1_name) VALUES('MySQL');
+
+SELECT * from t1;
+
+SHOW CREATE TABLE `t1`;
+
+DROP TABLE `t1`;
+
+--echo End of 4.1 tests

mysql-test/t/mysqldump.test

@@ -647,4 +647,34 @@ select * from t1;
 select * from t1;
 
 drop table t1;
-# End of 4.1 tests
+
+#
+# BUG #19025 mysqldump doesn't correctly dump "auto_increment = [int]"
+#
+create table `t1` (
+    t1_name varchar(255) default null,
+    t1_id int(10) unsigned not null auto_increment,
+    key (t1_name),
+    primary key (t1_id)
+) auto_increment = 1000 default charset=latin1;
+
+insert into t1 (t1_name) values('bla');
+insert into t1 (t1_name) values('bla');
+insert into t1 (t1_name) values('bla');
+
+select * from t1;
+
+show create table `t1`;
+
+--exec $MYSQL_DUMP --skip-comments test t1 > $MYSQLTEST_VARDIR/tmp/bug19025.sql
+DROP TABLE `t1`;
+
+--exec $MYSQL test < $MYSQLTEST_VARDIR/tmp/bug19025.sql
+
+select * from t1;
+
+show create table `t1`;
+
+drop table `t1`;
+
+--echo End of 4.1 tests

sql/sql_show.cc

@@ -1480,6 +1480,24 @@ store_create_info(THD *thd, TABLE *table, String *packet)
       packet->append(" ENGINE=", 8);
     packet->append(file->table_type());
     
+    /*
+      Add AUTO_INCREMENT=... if there is an AUTO_INCREMENT column,
+      and NEXT_ID > 1 (the default).  We must not print the clause
+      for engines that do not support this as it would break the
+      import of dumps, but as of this writing, the test for whether
+      AUTO_INCREMENT columns are allowed and wether AUTO_INCREMENT=...
+      is supported is identical, !(file->table_flags() & HA_NO_AUTO_INCREMENT))
+      Because of that, we do not explicitly test for the feature,
+      but may extrapolate its existence from that of an AUTO_INCREMENT column.
+    */
+
+    if(create_info.auto_increment_value > 1)
+    {
+      packet->append(" AUTO_INCREMENT=", 16);
+      end= longlong10_to_str(create_info.auto_increment_value, buff,10);
+      packet->append(buff, (uint) (end - buff));
+    }
+    
     if (table->table_charset &&
 	!(thd->variables.sql_mode & MODE_MYSQL323) &&
 	!(thd->variables.sql_mode & MODE_MYSQL40))