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If you create an NDB Cluster Disk Data table and then insert some rows into it, you can see approximately how much space remains for undo logging afterward, for example: 

mysql> CREATE TABLESPACE ts1 ADD DATAFILE ’data1.dat’ USE LOGFILE GROUP lg1 INITIAL_SIZE 512M ENGINE = NDB; 

mysql> CREATE TABLE dd ( c1 INT NOT NULL PRIMARY KEY, c2 INT, c3 DATE ) TABLESPACE ts1 STORAGE DISK ENGINE = NDB; 

mysql> INSERT INTO dd VALUES (NULL, 1234567890, ’2007-02-02’), (NULL, 1126789005, ’2007-02-03’), (NULL, 1357924680, ’2007-02-04’), (NULL, 1642097531, ’2007-02-05’); 

mysql> SELECT FREE_EXTENTS AS ’Free Extents’, FREE_EXTENTS * EXTENT_SIZE AS ’Free Bytes’ FROM INFORMATION_SCHEMA.FILES WHERE LOGFILE_GROUP_NAME = ’lg1’ AND FILE_NAME IS NULL; 

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•Prior to NDB 8.0.13, an additional row was present in the FILES  table for each NDB Cluster Disk Data tablespace. Because it did not correspond to an actual file, it was removed in NDB 8.0.13. This row had NULL  for the value of the FILE_NAME  column, the value of the FILE_ID  column was always 0 , that of the FILE_TYPE  column was always TABLESPACE , that of the STATUS  column was always NORMAL , and the value of the ENGINE  column is always NDBCLUSTER . 

In NDB 8.0.13 and later, you can obtain information about Disk Data tablespaces using the ndb_desc utility. For more information, see Section 23.5.10.1, “NDB Cluster Disk Data Objects” , as well as the description of ndb_desc . 

•For additional information, and examples of creating, dropping, and obtaining information about NDB Cluster Disk Data objects, see Section 23.5.10, “NDB Cluster Disk Data Tables” . 

## 26.3.16 The INFORMATION_SCHEMA KEY_COLUMN_USAGE Table 

The KEY_COLUMN_USAGE  table describes which key columns have constraints. This table provides no information about functional key parts because they are expressions and the table provides information only about columns. 

The KEY_COLUMN_USAGE  table has these columns: 

• CONSTRAINT_CATALOG 

