Bug #7142 Show Fields from fails using Borland's dbExpress interface

The problem here is that columns that have an especially long type 
such as an enum type with many options would be longer than 40 chars
but the type column returned from show columns always was defined
as varchar(40).

This is fixed in 5.0 using info schema.

mysql-test/r/ps_1general.result

@@ -470,12 +470,12 @@ def					id	8	3	1	N	32929	0	63
 def					select_type	253	19	6	N	1	31	8
 def					table	253	64	2	Y	0	31	8
 def					type	253	10	3	Y	0	31	8
-def					possible_keys	253	4096	0	Y	0	31	8
+def					possible_keys	252	4096	0	Y	0	31	8
 def					key	253	64	0	Y	0	31	8
 def					key_len	8	3	0	Y	32928	0	63
-def					ref	253	1024	0	Y	0	31	8
+def					ref	252	1024	0	Y	0	31	8
 def					rows	8	10	1	Y	32928	0	63
-def					Extra	253	255	14	N	1	31	8
+def					Extra	252	255	14	N	1	31	8
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	4	Using filesort
 SET @arg00=1 ;
@@ -486,12 +486,12 @@ def					id	8	3	1	N	32929	0	63
 def					select_type	253	19	6	N	1	31	8
 def					table	253	64	2	Y	0	31	8
 def					type	253	10	5	Y	0	31	8
-def					possible_keys	253	4096	7	Y	0	31	8
+def					possible_keys	252	4096	7	Y	0	31	8
 def					key	253	64	7	Y	0	31	8
 def					key_len	8	3	1	Y	32928	0	63
-def					ref	253	1024	0	Y	0	31	8
+def					ref	252	1024	0	Y	0	31	8
 def					rows	8	10	1	Y	32928	0	63
-def					Extra	253	255	27	N	1	31	8
+def					Extra	252	255	27	N	1	31	8
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	PRIMARY	PRIMARY	4	NULL	3	Using where; Using filesort
 drop table if exists t2;

mysql-test/r/ps_2myisam.result

@@ -1153,12 +1153,12 @@ def					id	8	3	1	N	32929	0	63
 def					select_type	253	19	6	N	1	31	8
 def					table	253	64	2	Y	0	31	8
 def					type	253	10	3	Y	0	31	8
-def					possible_keys	253	4096	0	Y	0	31	8
+def					possible_keys	252	4096	0	Y	0	31	8
 def					key	253	64	0	Y	0	31	8
 def					key_len	8	3	0	Y	32928	0	63
-def					ref	253	1024	0	Y	0	31	8
+def					ref	252	1024	0	Y	0	31	8
 def					rows	8	10	1	Y	32928	0	63
-def					Extra	253	255	0	N	1	31	8
+def					Extra	252	255	0	N	1	31	8
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t9	ALL	NULL	NULL	NULL	NULL	2	
 drop table if exists t2 ;

mysql-test/r/ps_3innodb.result

@@ -1153,12 +1153,12 @@ def					id	8	3	1	N	32929	0	63
 def					select_type	253	19	6	N	1	31	8
 def					table	253	64	2	Y	0	31	8
 def					type	253	10	3	Y	0	31	8
-def					possible_keys	253	4096	0	Y	0	31	8
+def					possible_keys	252	4096	0	Y	0	31	8
 def					key	253	64	0	Y	0	31	8
 def					key_len	8	3	0	Y	32928	0	63
-def					ref	253	1024	0	Y	0	31	8
+def					ref	252	1024	0	Y	0	31	8
 def					rows	8	10	1	Y	32928	0	63
-def					Extra	253	255	0	N	1	31	8
+def					Extra	252	255	0	N	1	31	8
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t9	ALL	NULL	NULL	NULL	NULL	2	
 test_sequence

mysql-test/r/ps_4heap.result

@@ -1154,12 +1154,12 @@ def					id	8	3	1	N	32929	0	63
 def					select_type	253	19	6	N	1	31	8
 def					table	253	64	2	Y	0	31	8
 def					type	253	10	3	Y	0	31	8
-def					possible_keys	253	4096	0	Y	0	31	8
+def					possible_keys	252	4096	0	Y	0	31	8
 def					key	253	64	0	Y	0	31	8
 def					key_len	8	3	0	Y	32928	0	63
-def					ref	253	1024	0	Y	0	31	8
+def					ref	252	1024	0	Y	0	31	8
 def					rows	8	10	1	Y	32928	0	63
-def					Extra	253	255	0	N	1	31	8
+def					Extra	252	255	0	N	1	31	8
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t9	ALL	NULL	NULL	NULL	NULL	2	
 test_sequence

mysql-test/r/ps_5merge.result

@@ -1196,12 +1196,12 @@ def					id	8	3	1	N	32929	0	63
 def					select_type	253	19	6	N	1	31	8
 def					table	253	64	2	Y	0	31	8
 def					type	253	10	3	Y	0	31	8
-def					possible_keys	253	4096	0	Y	0	31	8
+def					possible_keys	252	4096	0	Y	0	31	8
 def					key	253	64	0	Y	0	31	8
 def					key_len	8	3	0	Y	32928	0	63
-def					ref	253	1024	0	Y	0	31	8
+def					ref	252	1024	0	Y	0	31	8
 def					rows	8	10	1	Y	32928	0	63
-def					Extra	253	255	0	N	1	31	8
+def					Extra	252	255	0	N	1	31	8
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t9	ALL	NULL	NULL	NULL	NULL	2	
 test_sequence
@@ -4210,12 +4210,12 @@ def					id	8	3	1	N	32929	0	63
 def					select_type	253	19	6	N	1	31	8
 def					table	253	64	2	Y	0	31	8
 def					type	253	10	3	Y	0	31	8
-def					possible_keys	253	4096	0	Y	0	31	8
+def					possible_keys	252	4096	0	Y	0	31	8
 def					key	253	64	0	Y	0	31	8
 def					key_len	8	3	0	Y	32928	0	63
-def					ref	253	1024	0	Y	0	31	8
+def					ref	252	1024	0	Y	0	31	8
 def					rows	8	10	1	Y	32928	0	63
-def					Extra	253	255	0	N	1	31	8
+def					Extra	252	255	0	N	1	31	8
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t9	ALL	NULL	NULL	NULL	NULL	2	
 test_sequence

sql/item.cc

@@ -1768,7 +1768,14 @@ void Item::make_field(Send_field *tmp_field)
 
 void Item_empty_string::make_field(Send_field *tmp_field)
 {
-  init_make_field(tmp_field,FIELD_TYPE_VAR_STRING);
+  enum_field_types type = FIELD_TYPE_VAR_STRING;  
+  if (max_length >= 16777216)    
+    type = FIELD_TYPE_LONG_BLOB;  
+  else if (max_length >= 65536)    
+    type = FIELD_TYPE_MEDIUM_BLOB;  
+  else if (max_length >= 256)    
+    type = FIELD_TYPE_BLOB;  
+  init_make_field(tmp_field, type);
 }
 
 

sql/sql_show.cc

@@ -638,6 +638,30 @@ int mysqld_extend_show_tables(THD *thd,const char *db,const char *wild)
   DBUG_RETURN(0);
 }
 
+/*
+returns the length of the longest type on the given table.
+This is used so that show fields will return the data using the proper 
+lengths instead of forcing columns such as type to always return with a 
+given length.
+*/
+uint get_longest_type_in_table(TABLE *table, const char *wild)
+{  
+  Field **ptr,*field;  
+  char tmp[MAX_FIELD_WIDTH];  
+  uint max_len = 0;  
+
+  for (ptr=table->field; (field= *ptr); ptr++)  
+  {    
+    if (!wild || !wild[0] ||         
+        !wild_case_compare(system_charset_info, field->field_name,wild))    
+    {
+      String type(tmp,sizeof(tmp), system_charset_info);      
+      field->sql_type(type);      
+      max_len = max(max_len, type.length());     
+    }  
+  }  
+  return max_len;
+}
 
 /***************************************************************************
 ** List all columns in a table_list->real_name
@@ -667,9 +691,14 @@ mysqld_show_fields(THD *thd, TABLE_LIST *table_list,const char *wild,
 #ifndef NO_EMBEDDED_ACCESS_CHECKS
   (void) get_table_grant(thd, table_list);
 #endif
+
+  /* we scan for the longest since long enum types can exceed 40 */
+  uint max_len = get_longest_type_in_table(table, wild);
+
   List<Item> field_list;
   field_list.push_back(new Item_empty_string("Field",NAME_LEN));
-  field_list.push_back(new Item_empty_string("Type",40));
+  field_list.push_back(new Item_empty_string("Type",
+	max_len > 40 ? max_len : 40));
   if (verbose)
     field_list.push_back(new Item_empty_string("Collation",40));
   field_list.push_back(new Item_empty_string("Null",1));

tests/mysql_client_test.c

@@ -7173,7 +7173,7 @@ static void test_explain_bug()
   verify_prepare_field(result, 3, "type", "", MYSQL_TYPE_VAR_STRING,
                        "", "", "", 10, 0);
 
-  verify_prepare_field(result, 4, "possible_keys", "", MYSQL_TYPE_VAR_STRING,
+  verify_prepare_field(result, 4, "possible_keys", "", MYSQL_TYPE_BLOB,
                        "", "", "", NAME_LEN*64, 0);
 
   verify_prepare_field(result, 5, "key", "", MYSQL_TYPE_VAR_STRING,
@@ -7186,13 +7186,13 @@ static void test_explain_bug()
                        (mysql_get_server_version(mysql) <= 50000 ? 3 : 4096),
                        0);
 
-  verify_prepare_field(result, 7, "ref", "", MYSQL_TYPE_VAR_STRING,
+  verify_prepare_field(result, 7, "ref", "", MYSQL_TYPE_BLOB,
                        "", "", "", NAME_LEN*16, 0);
 
   verify_prepare_field(result, 8, "rows", "", MYSQL_TYPE_LONGLONG,
                        "", "", "", 10, 0);
 
-  verify_prepare_field(result, 9, "Extra", "", MYSQL_TYPE_VAR_STRING,
+  verify_prepare_field(result, 9, "Extra", "", MYSQL_TYPE_BLOB,
                        "", "", "", 255, 0);
 
   mysql_free_result(result);