set storage_engine = innodb;
# rebuild 600 data files in InnoDB.

mysql> SELECT count(*) FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE;
+----------+
| count(*) |
+----------+
|      945 |
+----------+
1 row in set (10.14 sec)

mysql> SELECT t1.referenced_table_name, t1.referenced_column_name, t0.ORDINAL_POSITION,
    -> t0.COLUMN_NAME, COLUMN_TYPE, IS_NULLABLE, EXTRA, COLUMN_DEFAULT, COLUMN_COMMENT
    -> FROM INFORMATION_SCHEMA.COLUMNS as t0
    -> left outer
    -> JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS t1
    -> ON t1.TABLE_SCHEMA =
    -> t0.TABLE_SCHEMA AND t1.TABLE_NAME = t0.TABLE_NAME AND t1.COLUMN_NAME = t0.COLUMN_NAME
    -> WHERE t0.TABLE_SCHEMA = schema() AND t0.TABLE_NAME = 'tt_1'
    -> ORDER BY t0.TABLE_NAME, t0.ORDINAL_POSITION, t0.COLUMN_NAME, DATA_TYPE,
    -> CHARACTER_MAXIMUM_LENGTH
    -> ;
Empty set (9.88 sec)

# I added temporary timing code to determine how much time was being spent in various 
# parts of the call stack.  These are the relevant results for the joined SELECT above.

sql_show.cc; get_all_tables()= 9.850884
  sql_show.cc; get_all_tables() for each db loop = 9.824409
  sql_show.cc; get_all_tables() for each table loop = 9.812224
  sql_show.cc; open_normal_and_derived_tables() = 0.824429  (719 calls)
  sql_show.cc; get_all_tables()->process_table() = 8.585035 (687 calls)
  sql_show.cc; get_all_tables()->process_table()-> 
               show_table->file->info(HA_STATUS_VARIABLE|HA_STATUS_NO_LOCK|HA_STATUS_TIME)
               = 8.506175 (687 calls)
    ha_innodb.cc; ha_innodb::info() = 8.507651 (1200 calls)
      ha_innodb.cc; ha_innodb::info()->if (HA_STATUS_TIME) = 8493860 (600 calls)
      ha_innodb.cc; ha_innodb::info()->if (HA_STATUS_VARIABLE) = 2181 (1200 calls)





mysql> set storage_engine = myisam;
# rebuild the data files in MyISAM.
mysql> SELECT count(*) FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE;
+----------+
| count(*) |
+----------+
|      945 |
+----------+
1 row in set (1.28 sec)
mysql> SELECT t1.referenced_table_name, t1.referenced_column_name, t0.ORDINAL_POSITION,
    -> t0.COLUMN_NAME, COLUMN_TYPE, IS_NULLABLE, EXTRA, COLUMN_DEFAULT, COLUMN_COMMENT
    -> FROM INFORMATION_SCHEMA.COLUMNS as t0
    -> left outer
    -> JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS t1
    -> ON t1.TABLE_SCHEMA =
    -> t0.TABLE_SCHEMA AND t1.TABLE_NAME = t0.TABLE_NAME AND t1.COLUMN_NAME = t0.COLUMN_NAME
    -> WHERE t0.TABLE_SCHEMA = schema() AND t0.TABLE_NAME = 'tt_1'
    -> ORDER BY t0.TABLE_NAME, t0.ORDINAL_POSITION, t0.COLUMN_NAME, DATA_TYPE,
    -> CHARACTER_MAXIMUM_LENGTH
    -> ;
Empty set (1.25 sec)

# I added temporary timing code to determine how much time was being spent in various 
# parts of the call stack.  These are the relevant results for the joined SELECT above.

sql_show.cc; get_all_tables()= 1.052377
  sql_show.cc; get_all_tables() for each db loop = 1.023079
  sql_show.cc; get_all_tables() for each table loop = 1.009371
  sql_show.cc; open_normal_and_derived_tables() = 0.738829  (719 calls)
  sql_show.cc; show_table->file->info(HA_STATUS_VARIABLE|HA_STATUS_NO_LOCK|HA_STATUS_TIME)
               = 0.019789 (687 calls)
    ha_myisam.cc; ha_myisam::info() = 0.029952 (1269 calls)
  sql_show.cc; get_all_tables()->process_table() = 0.048722 (687 calls)