Bug#22740093: ERROR 1071 (42000): SPECIFIED KEY WAS TOO LONG

jhauglid · jhauglid · commit 89041ce5430b · 2016-09-13T08:09:01.000+02:00
ERROR WHILE DROPPING INDEX IN 5.7

This bug concerns the check of index prefix lengths for TEXT
type columns. These types of columns has a maximum length
measured in bytes (e.g. 255 bytes for TINYTEXT). However the
index prefix length specified in CREATE TABLE and ALTER TABLE
statements is in characters.

This gave separate buggy behavior for CREATE TABLE and ALTER TABLE:

During CREATE TABLE, the index prefix length was only checked
against storage engine maximum sizes, not the maximum size of
the column (Create_field::key_length is still 0 when the
check was attempted). This e.g. meant that you could create a
prefix index of 768 utf8mb4 characters for TINYTEXT columns
even if the real maximum is 63 characters (255/4).
(768 * 4 = 3072 is the InnoDB max index length).

During ALTER TABLE, the check was broken for multibyte character
sets as we multiplied the maximum size of each column with
bytes_per_character one time too many. This e.g meant that at you
could add an index of 252 utf8mb4 characters for TINYTEXT
columns (63 * 4 = 252).

This patch fixes the problem by comparing the index prefix length
in bytes against the max column length in bytes. So for TINYTEXT,
the maximum prefix is now 63 regardless of whether CREATE TABLE or
ALTER TABLE is used to create the index (assuming a 4 byte
character set is used).
diff --git a/mysql-test/r/alter_table.result b/mysql-test/r/alter_table.result
@@ -1421,6 +1421,8 @@ DROP TABLE t1;
 DROP DATABASE IF EXISTS db1;
 CREATE DATABASE db1 CHARACTER SET utf8;
 CREATE TABLE db1.t1 (bar TINYTEXT, KEY (bar(100)));
+ERROR 42000: Specified key was too long; max key length is 255 bytes
+CREATE TABLE db1.t1 (bar TINYTEXT, KEY (bar(85)));
 ALTER TABLE db1.t1 ADD baz INT;
 DROP DATABASE db1;
 # Additional coverage for refactoring which is made as part
@@ -3497,3 +3499,28 @@ t1	CREATE TABLE `t1` (
   PRIMARY KEY (`fld1`)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8
 DROP TABLE t1;
+#
+# Bug#22740093: ERROR 1071 (42000): SPECIFIED KEY WAS TOO LONG
+#               ERROR WHILE DROPPING INDEX IN 5.7
+#
+CREATE TABLE t1(id INT PRIMARY KEY,
+name TINYTEXT,
+KEY nameloc (name(64))
+) DEFAULT CHARSET=utf8mb4;
+ERROR 42000: Specified key was too long; max key length is 255 bytes
+CREATE TABLE t1(id INT PRIMARY KEY,
+name TINYTEXT,
+KEY nameloc (name(63))
+) DEFAULT CHARSET=utf8mb4;
+ALTER TABLE t1 FORCE;
+ALTER TABLE t1 ADD INDEX idx (name(64), id);
+ERROR 42000: Specified key was too long; max key length is 255 bytes
+ALTER TABLE t1 ADD INDEX idx (name(63), id);
+DROP TABLE t1;
+CREATE TABLE t1(id INT PRIMARY KEY,
+name TEXT,
+KEY nameloc (name(64))
+) DEFAULT CHARSET=utf8mb4;
+ALTER TABLE t1 MODIFY COLUMN name TINYTEXT;
+ERROR 42000: Specified key was too long; max key length is 255 bytes
+DROP TABLE t1;
diff --git a/mysql-test/r/ctype_utf8.result b/mysql-test/r/ctype_utf8.result
@@ -2095,7 +2095,7 @@ CREATE TABLE t1 (
 clipid INT NOT NULL,
 Tape TINYTEXT,
 PRIMARY KEY (clipid),
-KEY tape(Tape(255))
+KEY tape(Tape(85))
 ) CHARACTER SET=utf8;
 ALTER TABLE t1 ADD mos TINYINT DEFAULT 0 AFTER clipid;
 SHOW CREATE TABLE t1;
@@ -2105,7 +2105,7 @@ t1	CREATE TABLE `t1` (
   `mos` tinyint(4) DEFAULT '0',
   `Tape` tinytext,
   PRIMARY KEY (`clipid`),
-  KEY `tape` (`Tape`(255))
+  KEY `tape` (`Tape`(85))
 ) ENGINE=MyISAM DEFAULT CHARSET=utf8
 DROP TABLE t1;
 DROP TABLE IF EXISTS t1;
diff --git a/mysql-test/r/ctype_utf8mb4.result b/mysql-test/r/ctype_utf8mb4.result
@@ -2244,7 +2244,7 @@ PRIMARY KEY (clipid),
 KEY tape(Tape(255))
 ) CHARACTER SET=utf8mb4;
 Warnings:
-Warning	1071	Specified key was too long; max key length is 1000 bytes
+Warning	1071	Specified key was too long; max key length is 255 bytes
 ALTER TABLE t1 ADD mos TINYINT DEFAULT 0 AFTER clipid;
 SHOW CREATE TABLE t1;
 Table	Create Table
@@ -2253,7 +2253,7 @@ t1	CREATE TABLE `t1` (
   `mos` tinyint(4) DEFAULT '0',
   `Tape` tinytext,
   PRIMARY KEY (`clipid`),
-  KEY `tape` (`Tape`(250))
+  KEY `tape` (`Tape`(63))
 ) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4
 DROP TABLE t1;
 SET sql_mode = default;
diff --git a/mysql-test/r/ctype_utf8mb4_innodb.result b/mysql-test/r/ctype_utf8mb4_innodb.result
@@ -2204,7 +2204,7 @@ PRIMARY KEY (clipid),
 KEY tape(Tape(255))
 ) CHARACTER SET=utf8mb4 ENGINE InnoDB;
 Warnings:
-Warning	1071	Specified key was too long; max key length is 767 bytes
+Warning	1071	Specified key was too long; max key length is 255 bytes
 ALTER TABLE t1 ADD mos TINYINT DEFAULT 0 AFTER clipid;
 SHOW CREATE TABLE t1;
 Table	Create Table
@@ -2213,7 +2213,7 @@ t1	CREATE TABLE `t1` (
   `mos` tinyint(4) DEFAULT '0',
   `Tape` tinytext,
   PRIMARY KEY (`clipid`),
-  KEY `tape` (`Tape`(191))
+  KEY `tape` (`Tape`(63))
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
 DROP TABLE t1;
 SET sql_mode = default;
diff --git a/mysql-test/r/ctype_utf8mb4_myisam.result b/mysql-test/r/ctype_utf8mb4_myisam.result
@@ -2201,7 +2201,7 @@ PRIMARY KEY (clipid),
 KEY tape(Tape(255))
 ) CHARACTER SET=utf8mb4 ENGINE MyISAM;
 Warnings:
-Warning	1071	Specified key was too long; max key length is 1000 bytes
+Warning	1071	Specified key was too long; max key length is 255 bytes
 ALTER TABLE t1 ADD mos TINYINT DEFAULT 0 AFTER clipid;
 SHOW CREATE TABLE t1;
 Table	Create Table
@@ -2210,7 +2210,7 @@ t1	CREATE TABLE `t1` (
   `mos` tinyint(4) DEFAULT '0',
   `Tape` tinytext,
   PRIMARY KEY (`clipid`),
-  KEY `tape` (`Tape`(250))
+  KEY `tape` (`Tape`(63))
 ) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4
 DROP TABLE t1;
 SET sql_mode = default;
diff --git a/mysql-test/suite/parts/inc/partition_blob.inc b/mysql-test/suite/parts/inc/partition_blob.inc
@@ -22,7 +22,7 @@ eval create table t2 (a blob not null, primary key(a(767))) engine=$engine
 partition by key (a) partitions 30;
 
 --error ER_BLOB_FIELD_IN_PART_FUNC_ERROR
-eval create table t2 (a tinyblob not null, primary key(a(767))) engine=$engine 
+eval create table t2 (a tinyblob not null, primary key(a(255))) engine=$engine 
 partition by key (a) partitions 30;
 
 --error ER_BLOB_FIELD_IN_PART_FUNC_ERROR
diff --git a/mysql-test/suite/parts/inc/partition_text.inc b/mysql-test/suite/parts/inc/partition_text.inc
@@ -18,7 +18,7 @@ partition pa4 max_rows=40 min_rows=2);
 #drop table t1;
 
 --error ER_BLOB_FIELD_IN_PART_FUNC_ERROR
-eval create table t2 (a tinytext not null, primary key(a(767))) engine=$engine 
+eval create table t2 (a tinytext not null, primary key(a(255))) engine=$engine 
 partition by key (a) partitions 30;
 
 --error ER_BLOB_FIELD_IN_PART_FUNC_ERROR
diff --git a/mysql-test/suite/parts/r/partition_char_innodb.result b/mysql-test/suite/parts/r/partition_char_innodb.result
@@ -733,7 +733,7 @@ ERROR HY000: A BLOB field is not allowed in partition function
 create table t2 (a blob not null, primary key(a(767))) engine='InnoDB' 
 partition by key (a) partitions 30;
 ERROR HY000: A BLOB field is not allowed in partition function
-create table t2 (a tinyblob not null, primary key(a(767))) engine='InnoDB' 
+create table t2 (a tinyblob not null, primary key(a(255))) engine='InnoDB' 
 partition by key (a) partitions 30;
 ERROR HY000: A BLOB field is not allowed in partition function
 create table t2 (a mediumblob not null, primary key(a(767))) engine='InnoDB' 
@@ -750,7 +750,7 @@ partition pa2 max_rows=30 min_rows=3,
 partition pa3 max_rows=30 min_rows=4,
 partition pa4 max_rows=40 min_rows=2);
 ERROR HY000: A BLOB field is not allowed in partition function
-create table t2 (a tinytext not null, primary key(a(767))) engine='InnoDB' 
+create table t2 (a tinytext not null, primary key(a(255))) engine='InnoDB' 
 partition by key (a) partitions 30;
 ERROR HY000: A BLOB field is not allowed in partition function
 create table t2 (a mediumtext not null, primary key(a(767))) engine='InnoDB' 
diff --git a/mysql-test/suite/parts/r/partition_char_myisam.result b/mysql-test/suite/parts/r/partition_char_myisam.result
@@ -733,7 +733,7 @@ ERROR HY000: A BLOB field is not allowed in partition function
 create table t2 (a blob not null, primary key(a(767))) engine='MyISAM' 
 partition by key (a) partitions 30;
 ERROR HY000: A BLOB field is not allowed in partition function
-create table t2 (a tinyblob not null, primary key(a(767))) engine='MyISAM' 
+create table t2 (a tinyblob not null, primary key(a(255))) engine='MyISAM' 
 partition by key (a) partitions 30;
 ERROR HY000: A BLOB field is not allowed in partition function
 create table t2 (a mediumblob not null, primary key(a(767))) engine='MyISAM' 
@@ -750,7 +750,7 @@ partition pa2 max_rows=30 min_rows=3,
 partition pa3 max_rows=30 min_rows=4,
 partition pa4 max_rows=40 min_rows=2);
 ERROR HY000: A BLOB field is not allowed in partition function
-create table t2 (a tinytext not null, primary key(a(767))) engine='MyISAM' 
+create table t2 (a tinytext not null, primary key(a(255))) engine='MyISAM' 
 partition by key (a) partitions 30;
 ERROR HY000: A BLOB field is not allowed in partition function
 create table t2 (a mediumtext not null, primary key(a(767))) engine='MyISAM' 
diff --git a/mysql-test/t/alter_table.test b/mysql-test/t/alter_table.test
@@ -1177,7 +1177,9 @@ DROP DATABASE IF EXISTS db1;
 --enable_warnings
 
 CREATE DATABASE db1 CHARACTER SET utf8;
+--error ER_TOO_LONG_KEY
 CREATE TABLE db1.t1 (bar TINYTEXT, KEY (bar(100)));
+CREATE TABLE db1.t1 (bar TINYTEXT, KEY (bar(85)));
 ALTER TABLE db1.t1 ADD baz INT;
 
 DROP DATABASE db1;
@@ -2804,3 +2806,48 @@ let $test_dir =
 --list_files $test_dir `#sql-*.frm`
 
 DROP TABLE t1;
+
+--echo #
+--echo # Bug#22740093: ERROR 1071 (42000): SPECIFIED KEY WAS TOO LONG
+--echo #               ERROR WHILE DROPPING INDEX IN 5.7
+--echo #
+
+# Before you were allowed to create a prefix key for TEXT columns
+# which were larger than the column length. The column length
+# for TINYBLOB is 255 bytes, while prefix length is in characters.
+--error ER_TOO_LONG_KEY
+CREATE TABLE t1(id INT PRIMARY KEY,
+                name TINYTEXT,
+                KEY nameloc (name(64))
+) DEFAULT CHARSET=utf8mb4;
+
+# 63 characters of 4 bytes each fit in 255 bytes.
+CREATE TABLE t1(id INT PRIMARY KEY,
+                name TINYTEXT,
+                KEY nameloc (name(63))
+) DEFAULT CHARSET=utf8mb4;
+
+# Check that we can rebuild the table without issue
+ALTER TABLE t1 FORCE;
+
+# Also check ALTER TABLE
+--error ER_TOO_LONG_KEY
+ALTER TABLE t1 ADD INDEX idx (name(64), id);
+ALTER TABLE t1 ADD INDEX idx (name(63), id);
+DROP TABLE t1;
+
+# Check that we can create a table with a prefix index of
+# 64 4-byte characters for a TEXT column.
+
+# 64 characters of 4 bytes each fit in 65535 bytes.
+CREATE TABLE t1(id INT PRIMARY KEY,
+                name TEXT,
+                KEY nameloc (name(64))
+) DEFAULT CHARSET=utf8mb4;
+
+# Check ALTER TABLE where we change the type of the
+# base column, reducing max field length, keeping the
+# length of the prefix key the same.
+--error ER_TOO_LONG_KEY
+ALTER TABLE t1 MODIFY COLUMN name TINYTEXT;
+DROP TABLE t1;
diff --git a/mysql-test/t/ctype_utf8.test b/mysql-test/t/ctype_utf8.test
@@ -1530,7 +1530,7 @@ CREATE TABLE t1 (
   clipid INT NOT NULL,
   Tape TINYTEXT,
   PRIMARY KEY (clipid),
-  KEY tape(Tape(255))
+  KEY tape(Tape(85))
 ) CHARACTER SET=utf8;
 ALTER TABLE t1 ADD mos TINYINT DEFAULT 0 AFTER clipid;
 SHOW CREATE TABLE t1;
diff --git a/sql/sql_table.cc b/sql/sql_table.cc
@@ -96,6 +96,7 @@ mysql_prepare_create_table(THD *thd, HA_CREATE_INFO *create_info,
                            uint *db_options,
                            handler *file, KEY **key_info_buffer,
                            uint *key_count, int select_field_count);
+static uint blob_length_by_type(enum_field_types type);
 
 
 /**
@@ -4298,8 +4299,8 @@ mysql_prepare_create_table(THD *thd, HA_CREATE_INFO *create_info,
             than the BLOB field max size. We handle this case
             using the max_field_size variable below.
           */
-          size_t max_field_size= sql_field->key_length * sql_field->charset->mbmaxlen;
-	  if ((max_field_size && key_part_length > max_field_size) ||
+          size_t max_field_size= blob_length_by_type(sql_field->sql_type);
+	  if (key_part_length > max_field_size ||
               key_part_length > max_key_length ||
 	      key_part_length > file->max_key_part_length())
 	  {
