• MySQL 5.1 Reference Manual :: 17 MySQL Cluster NDB 6.X/7.X :: 17.4 MySQL Cluster Programs :: 17.4.9 ndb_desc — Describe NDB Tables
  • 17.4.9. ndb_desc — Describe NDB Tables

    ndb_desc provides a detailed description of one or more NDB tables.

    Usage:

    ndb_desc -c connect_string tbl_name -d db_name [-p]
    

    Sample Output:

    MySQL table creation and population statements:

    USE test;
    
    CREATE TABLE fish (
        id INT(11) NOT NULL AUTO_INCREMENT,
        name VARCHAR(20) NOT NULL,
        length_mm INT(11) NOT NULL,
        weight_gm INT(11) NOT NULL,
    
        PRIMARY KEY pk (id),
        UNIQUE KEY uk (name)
    ) ENGINE=NDB;
    
    INSERT INTO fish VALUES
        ('','guppy', 35, 2), ('','tuna', 2500, 150000),
        ('','shark', 3000, 110000), ('','manta ray', 1500, 50000),
        ('','grouper', 900, 125000), ('','puffer', 250, 2500);
    

    Output from ndb_desc:

    shell> ./ndb_desc -c localhost fish -d test -p
    -- fish --
    Version: 2
    Fragment type: 9
    K Value: 6
    Min load factor: 78
    Max load factor: 80
    Temporary table: no
    Number of attributes: 4
    Number of primary keys: 1
    Length of frm data: 311
    Row Checksum: 1
    Row GCI: 1
    SingleUserMode: 0
    ForceVarPart: 1
    FragmentCount: 2
    TableStatus: Retrieved
    -- Attributes --
    id Int PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY AUTO_INCR
    name Varchar(20;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
    length_mm Int NOT NULL AT=FIXED ST=MEMORY
    weight_gm Int NOT NULL AT=FIXED ST=MEMORY
    
    -- Indexes --
    PRIMARY KEY(id) - UniqueHashIndex
    PRIMARY(id) - OrderedIndex
    uk$unique(name) - UniqueHashIndex
    uk(name) - OrderedIndex
    
    -- Per partition info --
    Partition  Row count  Commit count  Frag fixed memory  Frag varsized memory  Extent_space  Free extent_space
    0          2          2             32768              32768                 0             0
    1          4          4             32768              32768                 0             0
    
    NDBT_ProgramExit: 0 - OK
    

    Information about multiple tables can be obtained in a single invocation of ndb_desc by using their names, separated by spaces. All of the tables must be in the same database.

    The Extent_space and Free extent_space columns were added in MySQL Cluster NDB 6.3.27 and MySQL Cluster NDB 7.0.8. They are applicable only to NDB tables having columns on disk; for tables having only in-memory columns, these columns always contain the value 0.

    To illustrate their use, we modify the previous example. First, we must create the necessary Disk Data objects, as shown here:

    CREATE LOGFILE GROUP lg_1
        ADD UNDOFILE 'undo_1.log'
        INITIAL_SIZE 16M
        UNDO_BUFFER_SIZE 2M
        ENGINE NDB;
    
    ALTER LOGFILE GROUP lg_1
        ADD UNDOFILE 'undo_2.log'
        INITIAL_SIZE 12M
        ENGINE NDB;
    
    CREATE TABLESPACE ts_1
        ADD DATAFILE 'data_1.dat'
        USE LOGFILE GROUP lg_1
        INITIAL_SIZE 32M
        ENGINE NDB;
    
    ALTER TABLESPACE ts_1
        ADD DATAFILE 'data_2.dat'
        INITIAL_SIZE 48M
        ENGINE NDB;
    

    (For more information on the statements just shown and the objects created by them, see Section 17.5.10.1, “MySQL Cluster Disk Data Objects”, as well as Section 12.1.14, “CREATE LOGFILE GROUP Syntax”, and Section 12.1.18, “CREATE TABLESPACE Syntax”.)

    Now we can create and populate a version of the fish table that stores 2 of its columns on disk (deleting the previous version of the table first, if it already exists):

    CREATE TABLE fish (
        id INT(11) NOT NULL AUTO_INCREMENT,
        name VARCHAR(20) NOT NULL,
        length_mm INT(11) NOT NULL,
        weight_gm INT(11) NOT NULL,
    
        PRIMARY KEY pk (id),
        UNIQUE KEY uk (name)
    ) TABLESPACE ts_1 STORAGE DISK 
    ENGINE=NDB;
    
    INSERT INTO fish VALUES
        ('','guppy', 35, 2), ('','tuna', 2500, 150000),
        ('','shark', 3000, 110000), ('','manta ray', 1500, 50000),
        ('','grouper', 900, 125000), ('','puffer', 250, 2500);
    

    When run against this version of the table, ndb_desc displays the following output:

    shell> ./ndb_desc -c localhost fish -d test -p
    -- fish --
    Version: 3
    Fragment type: 9
    K Value: 6
    Min load factor: 78
    Max load factor: 80
    Temporary table: no
    Number of attributes: 4
    Number of primary keys: 1
    Length of frm data: 321
    Row Checksum: 1
    Row GCI: 1
    SingleUserMode: 0
    ForceVarPart: 1
    FragmentCount: 2
    TableStatus: Retrieved
    -- Attributes --
    id Int PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY AUTO_INCR
    name Varchar(20;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
    length_mm Int NOT NULL AT=FIXED ST=DISK
    weight_gm Int NOT NULL AT=FIXED ST=DISK
    
    -- Indexes --
    PRIMARY KEY(id) - UniqueHashIndex
    PRIMARY(id) - OrderedIndex
    uk$unique(name) - UniqueHashIndex
    uk(name) - OrderedIndex
    
    -- Per partition info --
    Partition  Row count  Commit count  Frag fixed memory  Frag varsized memory  Extent_space  Free extent_space
    0          2          2             32768              32768                 1048576       1044440
    1          4          4             32768              32768                 1048576       1044400
    
    NDBT_ProgramExit: 0 - OK
    

    This means that 1048576 bytes are allocated from the tablespace for this table on each partition, of which 1044440 bytes remain free for additional storage. In other words, 1048576 - 1044440 = 4136 bytes per partition is currently being used to store the data from this table's disk-based columns. The number of bytes shown as Free extent_space is available for storing on-disk column data from the fish table only; for this reason, it is not visible when selecting from the INFORMATION_SCHEMA.FILES table.

    Additional Options:

    • --extra-partition-info, -p

      Print additional information about the table's partitions.

    • --blob-info, -b

      Include information about subordinate BLOB and TEXT columns.

      Use of this option also requires the use of the --extra-partition-info (-p) option.

      This option was added in MySQL Cluster NDB 6.3.32, MySQL Cluster NDB 7.0.13, and MySQL Cluster NDB 7.1.2.

    • --extra-node-info, -n

      Include information about the mappings between table partitions and the data nodes upon which they reside. This information can be useful for verifying distribution awareness mechanisms and supporting more efficient application access to the data stored in MySQL Cluster.

      Use of this option also requires the use of the --extra-partition-info (-p) option.

      This option was added in MySQL Cluster NDB 6.2.19, MySQL Cluster NDB 6.3.33, MySQL Cluster NDB 7.0.14, and MySQL Cluster NDB 7.1.2.