Fix for bug#23037 Bug in field "Default" of query "SHOW COLUMNS FROM table"

  
To the documentor: The DEFAULT value in SHOW COLUMNS/SELECT FROM I_S.COLUMNS
was truncated to NAME_LEN (which effectively is 64) characters.

mysql-test/r/information_schema.result

@@ -737,6 +737,7 @@ select table_schema,table_name, column_name from
 information_schema.columns 
 where data_type = 'longtext';
 table_schema	table_name	column_name
+information_schema	COLUMNS	COLUMN_DEFAULT
 information_schema	COLUMNS	COLUMN_TYPE
 information_schema	ROUTINES	ROUTINE_DEFINITION
 information_schema	ROUTINES	SQL_MODE
@@ -1240,3 +1241,16 @@ WHERE table_name=(SELECT MAX(table_name)
 FROM information_schema.tables);
 table_name
 VIEWS
+DROP TABLE IF EXISTS bug23037;
+DROP FUNCTION IF EXISTS get_value;
+SELECT COLUMN_NAME, MD5(COLUMN_DEFAULT), LENGTH(COLUMN_DEFAULT) FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME='bug23037';
+COLUMN_NAME	MD5(COLUMN_DEFAULT)	LENGTH(COLUMN_DEFAULT)
+fld1	7cf7a6782be951a1f2464a350da926a5	65532
+SELECT MD5(get_value());
+MD5(get_value())
+7cf7a6782be951a1f2464a350da926a5
+SELECT COLUMN_NAME, MD5(COLUMN_DEFAULT), LENGTH(COLUMN_DEFAULT), COLUMN_DEFAULT=get_value() FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME='bug23037';
+COLUMN_NAME	MD5(COLUMN_DEFAULT)	LENGTH(COLUMN_DEFAULT)	COLUMN_DEFAULT=get_value()
+fld1	7cf7a6782be951a1f2464a350da926a5	65532	1
+DROP TABLE bug23037;
+DROP FUNCTION get_value;

mysql-test/t/information_schema.test

@@ -930,4 +930,47 @@ SELECT table_name from information_schema.tables
   WHERE table_name=(SELECT MAX(table_name)
                       FROM information_schema.tables);
 
+#
+# Bug #23037: Bug in field "Default" of query "SHOW COLUMNS FROM table"
+#
+# Note, MyISAM/InnoDB can't take more that 65532 chars, because the row
+# size is limited to 65535 bytes (BLOBs not counted)
+#
+--disable_warnings
+DROP TABLE IF EXISTS bug23037;
+DROP FUNCTION IF EXISTS get_value;
+--enable_warnings
+--disable_query_log
+DELIMITER |;
+CREATE FUNCTION get_value()
+  RETURNS TEXT
+  DETERMINISTIC
+BEGIN
+  DECLARE col1, col2, col3, col4, col6 CHAR(255);
+  DECLARE default_val VARCHAR(65532);
+  DECLARE done INT DEFAULT 0;
+  DECLARE cur1 CURSOR FOR SHOW COLUMNS FROM bug23037;
+  DECLARE CONTINUE HANDLER FOR SQLSTATE '02000' SET done = 1;
+  OPEN cur1;
+  FETCH cur1 INTO col1, col2, col3, col4, default_val, col6;
+  CLOSE cur1;
+  RETURN default_val;
+end|
+DELIMITER ;|
+
+let $body=`SELECT REPEAT('A', 65532)`;
+eval CREATE TABLE bug23037(fld1 VARCHAR(65532) CHARACTER SET latin1 DEFAULT "$body");
+--enable_query_log
+
+SELECT COLUMN_NAME, MD5(COLUMN_DEFAULT), LENGTH(COLUMN_DEFAULT) FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME='bug23037';
+
+SELECT MD5(get_value());
+
+SELECT COLUMN_NAME, MD5(COLUMN_DEFAULT), LENGTH(COLUMN_DEFAULT), COLUMN_DEFAULT=get_value() FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME='bug23037';
+
+DROP TABLE bug23037;
+DROP FUNCTION get_value;
+
+
+
 # End of 5.0 tests.

sql/sql_show.cc

@@ -4044,7 +4044,7 @@ ST_FIELD_INFO columns_fields_info[]=
   {"TABLE_NAME", NAME_LEN, MYSQL_TYPE_STRING, 0, 0, 0},
   {"COLUMN_NAME", NAME_LEN, MYSQL_TYPE_STRING, 0, 0, "Field"},
   {"ORDINAL_POSITION", 21 , MYSQL_TYPE_LONG, 0, 0, 0},
-  {"COLUMN_DEFAULT", NAME_LEN, MYSQL_TYPE_STRING, 0, 1, "Default"},
+  {"COLUMN_DEFAULT", MAX_FIELD_VARCHARLENGTH, MYSQL_TYPE_STRING, 0, 1, "Default"},
   {"IS_NULLABLE", 3, MYSQL_TYPE_STRING, 0, 0, "Null"},
   {"DATA_TYPE", NAME_LEN, MYSQL_TYPE_STRING, 0, 0, 0},
   {"CHARACTER_MAXIMUM_LENGTH", 21 , MYSQL_TYPE_LONG, 0, 1, 0},