Bug#8283 - OPTIMIZE TABLE causes data loss

OPTIMIZE TABLE with myisam_repair_threads > 1 performs a non-quick 
parallel repair. This means that it does not only rebuild all 
indexes, but also the data file.

Non-quick parallel repair works so that there is one thread per 
index. The first of the threads rebuilds also the new data file.

The problem was that all threads shared the read io cache on the
old data file. If there were holes (deleted records) in the table,
the first thread skipped them, writing only contiguous, non-deleted
records to the new data file. Then it built the new index so that
its entries pointed to the correct record positions. But the other
threads didn't know the new record positions, but put the positions
from the old data file into the index.

The new design is so that there is a shared io cache which is filled
by the first thread (the data file writer) with the new contiguous
records and read by the other threads. Now they know the new record
positions.

Another problem was that for the parallel repair of compressed
tables a common bit_buff and rec_buff was used. I changed it so
that thread specific buffers are used for parallel repair.

A similar problem existed for checksum calculation. I made this
multi-thread safe too.


include/my_sys.h:
  Bug#8283 - OPTIMIZE TABLE causes data loss
  Redesign of io_cache_share.
include/myisam.h:
  Bug#8283 - OPTIMIZE TABLE causes data loss
  Redesign of checksum calculation in mi_check.c.
  'calc_checksum' is now in myisamdef.h:st_mi_sort_param.
myisam/mi_check.c:
  Bug#8283 - OPTIMIZE TABLE causes data loss
  Implemented a new parallel repair design.
  Using a synchronized shared read/write cache.
  Allowed for thread specific bit_buff, rec_buff, and calc_checksum.
myisam/mi_open.c:
  Bug#8283 - OPTIMIZE TABLE causes data loss
  Added DBUG output.
myisam/mi_packrec.c:
  Bug#8283 - OPTIMIZE TABLE causes data loss
  Allowed for thread specific bit_buff and rec_buff.
myisam/myisamdef.h:
  Bug#8283 - OPTIMIZE TABLE causes data loss
  Commented on checksum calculation variables.
  Allowed for thread specific bit_buff.
  Added DBUG output for better table crash detection.
myisam/sort.c:
  Bug#8283 - OPTIMIZE TABLE causes data loss
  Added implications of the new parallel repair design.
  Renamed 'info' -> 'sort_param'.
  Added DBUG output.
mysql-test/r/myisam.result:
  Bug#8283 - OPTIMIZE TABLE causes data loss
  Added test results.
mysql-test/t/myisam.test:
  Bug#8283 - OPTIMIZE TABLE causes data loss
  Added test cases.
mysys/mf_iocache.c:
  Bug#8283 - OPTIMIZE TABLE causes data loss
  Redesign of io_cache_share.
  We do now allow a writer to synchronize himself with the
  readers of a shared cache. When all threads join in the lock,
  the writer copies the data from his write buffer to the shared
  read buffer.

1 files changed, 93 insertions, 0 deletions

diff --git a/mysql-test/t/myisam.test b/mysql-test/t/myisam.test
index 5f948973141..0b9fad07ac4 100644
--- a/mysql-test/t/myisam.test
+++ b/mysql-test/t/myisam.test
@@ -714,4 +714,97 @@ UPDATE t1 AS ta1,t1 AS ta2 SET ta1.b='aaaaaa',ta2.b='bbbbbb';
 SELECT * FROM t1;
 DROP TABLE t1;
 
+#
+# Bug#8283 - OPTIMIZE TABLE causes data loss
+#
+SET @@myisam_repair_threads=2;
+SHOW VARIABLES LIKE 'myisam_repair%';
+#
+# Test OPTIMIZE. This creates a new data file.
+CREATE TABLE t1 (
+  `_id` int(11) NOT NULL default '0',
+  `url` text,
+  `email` text,
+  `description` text,
+  `loverlap` int(11) default NULL,
+  `roverlap` int(11) default NULL,
+  `lneighbor_id` int(11) default NULL,
+  `rneighbor_id` int(11) default NULL,
+  `length_` int(11) default NULL,
+  `sequence` mediumtext,
+  `name` text,
+  `_obj_class` text NOT NULL,
+  PRIMARY KEY  (`_id`),
+  UNIQUE KEY `sequence_name_index` (`name`(50)),
+  KEY (`length_`)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1;
+#
+INSERT INTO t1 VALUES
+  (1,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,'sample1',''),
+  (2,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,'sample2',''),
+  (3,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,'sample3',''),
+  (4,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,'sample4',''),
+  (5,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,'sample5',''),
+  (6,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,'sample6',''),
+  (7,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,'sample7',''),
+  (8,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,'sample8',''),
+  (9,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,'sample9','');
+#
+SELECT _id FROM t1;
+DELETE FROM t1 WHERE _id < 8;
+--replace_column 6 # 7 # 8 # 9 # 11 # 12 # 13 # 14 # 15 # 16 #
+SHOW TABLE STATUS LIKE 't1';
+CHECK TABLE t1 EXTENDED;
+OPTIMIZE TABLE t1;
+CHECK TABLE t1 EXTENDED;
+--replace_column 6 # 7 # 8 # 9 # 11 # 12 # 13 # 14 # 15 # 16 #
+SHOW TABLE STATUS LIKE 't1';
+SELECT _id FROM t1;
+DROP TABLE t1;
+#
+# Test REPAIR QUICK. This retains the old data file.
+CREATE TABLE t1 (
+  `_id` int(11) NOT NULL default '0',
+  `url` text,
+  `email` text,
+  `description` text,
+  `loverlap` int(11) default NULL,
+  `roverlap` int(11) default NULL,
+  `lneighbor_id` int(11) default NULL,
+  `rneighbor_id` int(11) default NULL,
+  `length_` int(11) default NULL,
+  `sequence` mediumtext,
+  `name` text,
+  `_obj_class` text NOT NULL,
+  PRIMARY KEY  (`_id`),
+  UNIQUE KEY `sequence_name_index` (`name`(50)),
+  KEY (`length_`)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1;
+#
+INSERT INTO t1 VALUES
+  (1,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,'sample1',''),
+  (2,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,'sample2',''),
+  (3,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,'sample3',''),
+  (4,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,'sample4',''),
+  (5,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,'sample5',''),
+  (6,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,'sample6',''),
+  (7,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,'sample7',''),
+  (8,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,'sample8',''),
+  (9,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,'sample9','');
+#
+SELECT _id FROM t1;
+DELETE FROM t1 WHERE _id < 8;
+--replace_column 6 # 7 # 8 # 9 # 11 # 12 # 13 # 14 # 15 # 16 #
+SHOW TABLE STATUS LIKE 't1';
+CHECK TABLE t1 EXTENDED;
+REPAIR TABLE t1 QUICK;
+CHECK TABLE t1 EXTENDED;
+--replace_column 6 # 7 # 8 # 9 # 11 # 12 # 13 # 14 # 15 # 16 #
+SHOW TABLE STATUS LIKE 't1';
+SELECT _id FROM t1;
+DROP TABLE t1;
+#
+SET @@myisam_repair_threads=1;
+SHOW VARIABLES LIKE 'myisam_repair%';
+
 # End of 4.1 tests