21.4.10 ndb_desc — Describe NDB Tables
ndb_desc provides a detailed description of one or more NDB
tables.
Usage
ndb_desc -c connection_string tbl_name -d db_name [options]
ndb_desc -c connection_string index_name -d db_name -t tbl_name
Additional options that can be used with ndb_desc are listed later in this section.
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
(NULL, 'guppy', 35, 2), (NULL, 'tuna', 2500, 150000),
(NULL, 'shark', 3000, 110000), (NULL, 'manta ray', 1500, 50000),
(NULL, 'grouper', 900, 125000), (NULL ,'puffer', 250, 2500);
Output from ndb_desc:
shell> ./ndb_desc -c localhost fish -d test -p
-- fish --
Version: 2
Fragment type: HashMapPartition
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: 337
Max Rows: 0
Row Checksum: 1
Row GCI: 1
SingleUserMode: 0
ForceVarPart: 1
PartitionCount: 2
FragmentCount: 2
PartitionBalance: FOR_RP_BY_LDM
ExtraRowGciBits: 0
ExtraRowAuthorBits: 0
TableStatus: Retrieved
Table options:
HashMap: DEFAULT-HASHMAP-3840-2
-- 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 DYNAMIC
length_mm Int NOT NULL AT=FIXED ST=MEMORY DYNAMIC
weight_gm Int NOT NULL AT=FIXED ST=MEMORY DYNAMIC
-- Indexes --
PRIMARY KEY(id) - UniqueHashIndex
PRIMARY(id) - OrderedIndex
uk(name) - OrderedIndex
uk$unique(name) - UniqueHashIndex
-- Per partition info --
Partition Row count Commit count Frag fixed memory Frag varsized memory Extent_space Free extent_space
0 2 2 32768 32768 0 0
1 4 4 32768 32768 0 0
NDBT_ProgramExit: 0 - OK
Information about multiple tables can be obtained in a single invocation of ndb_desc by using their names, separated by spaces. All of the tables must be in the same database.
You can obtain additional information about a specific index using the --table
(short form: -t
) option and supplying the name of the index as the first argument to ndb_desc, as shown here:
shell> ./ndb_desc uk -d test -t fish
-- uk --
Version: 2
Base table: fish
Number of attributes: 1
Logging: 0
Index type: OrderedIndex
Index status: Retrieved
-- Attributes --
name Varchar(20;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
-- IndexTable 10/uk --
Version: 2
Fragment type: FragUndefined
K Value: 6
Min load factor: 78
Max load factor: 80
Temporary table: yes
Number of attributes: 2
Number of primary keys: 1
Length of frm data: 0
Max Rows: 0
Row Checksum: 1
Row GCI: 1
SingleUserMode: 2
ForceVarPart: 0
PartitionCount: 2
FragmentCount: 2
FragmentCountType: ONE_PER_LDM_PER_NODE
ExtraRowGciBits: 0
ExtraRowAuthorBits: 0
TableStatus: Retrieved
Table options:
-- Attributes --
name Varchar(20;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
NDB$TNODE Unsigned [64] PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY
-- Indexes --
PRIMARY KEY(NDB$TNODE) - UniqueHashIndex
NDBT_ProgramExit: 0 - OK
When an index is specified in this way, the --extra-partition-info
and --extra-node-info
options have no effect.
The Version
column in the output contains the table's schema object version. For information about interpreting this value, see NDB Schema Object Versions .
Three of the table properties that can be set using NDB_TABLE
comments embedded in CREATE TABLE
and ALTER TABLE
statements are also visible in ndb_desc output. The table's FRAGMENT_COUNT_TYPE
is always shown in the FragmentCountType
column. READ_ONLY
and FULLY_REPLICATED
, if set to 1, are shown in the Table options
column. You can see this after executing the following ALTER TABLE
statement in the mysql client:
mysql> ALTER TABLE fish COMMENT='NDB_TABLE=READ_ONLY=1,FULLY_REPLICATED=1';
1 row in set, 1 warning (0.00 sec)
mysql> SHOW WARNINGS\G
+---------+------+---------------------------------------------------------------------------------------------------------+
| Level | Code | Message |
+---------+------+---------------------------------------------------------------------------------------------------------+
| Warning | 1296 | Got error 4503 'Table property is FRAGMENT_COUNT_TYPE=ONE_PER_LDM_PER_NODE but not in comment' from NDB |
+---------+------+---------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
The warning is issued because READ_ONLY=1
requires that the table's fragment count type is (or be set to) ONE_PER_LDM_PER_NODE_GROUP
; NDB
sets this automatically in such cases. You can check that the ALTER TABLE
statement has the desired effect using SHOW CREATE TABLE
:
mysql> SHOW CREATE TABLE fish\G
*************************** 1. row ***************************
Table: fish
Create Table: 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 (`id`),
UNIQUE KEY `uk` (`name`)
) ENGINE=ndbcluster DEFAULT CHARSET=latin1
COMMENT='NDB_TABLE=READ_BACKUP=1,FULLY_REPLICATED=1'
1 row in set (0.01 sec)
Because FRAGMENT_COUNT_TYPE
was not set explicitly, its value is not shown in the comment text printed by SHOW CREATE TABLE
. ndb_desc, however, displays the updated value for this attribute. The Table options
column shows the binary properties just enabled. You can see this in the output shown here (emphasized text):
shell> ./ndb_desc -c localhost fish -d test -p
-- fish --
Version: 4
Fragment type: HashMapPartition
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: 380
Max Rows: 0
Row Checksum: 1
Row GCI: 1
SingleUserMode: 0
ForceVarPart: 1
PartitionCount: 1
FragmentCount: 1
FragmentCountType: ONE_PER_LDM_PER_NODE_GROUP
ExtraRowGciBits: 0
ExtraRowAuthorBits: 0
TableStatus: Retrieved
Table options: readbackup, fullyreplicated
HashMap: DEFAULT-HASHMAP-3840-1
-- 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 DYNAMIC
length_mm Int NOT NULL AT=FIXED ST=MEMORY DYNAMIC
weight_gm Int NOT NULL AT=FIXED ST=MEMORY DYNAMIC
-- Indexes --
PRIMARY KEY(id) - UniqueHashIndex
PRIMARY(id) - OrderedIndex
uk(name) - OrderedIndex
uk$unique(name) - UniqueHashIndex
-- Per partition info --
Partition Row count Commit count Frag fixed memory Frag varsized memory Extent_space Free extent_space
NDBT_ProgramExit: 0 - OK
For more information about these table properties, see Section 13.1.18.9, “Setting NDB_TABLE Options”.
The Extent_space
and Free extent_space
columns 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 21.5.10.1, “NDB Cluster Disk Data Objects”, as well as Section 13.1.15, “CREATE LOGFILE GROUP Statement”, and Section 13.1.19, “CREATE TABLESPACE Statement”.)
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
(NULL, 'guppy', 35, 2), (NULL, 'tuna', 2500, 150000),
(NULL, 'shark', 3000, 110000), (NULL, 'manta ray', 1500, 50000),
(NULL, 'grouper', 900, 125000), (NULL ,'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: 1
Fragment type: HashMapPartition
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: 346
Max Rows: 0
Row Checksum: 1
Row GCI: 1
SingleUserMode: 0
ForceVarPart: 1
PartitionCount: 2
FragmentCount: 2
FragmentCountType: ONE_PER_LDM_PER_NODE
ExtraRowGciBits: 0
ExtraRowAuthorBits: 0
TableStatus: Retrieved
Table options:
HashMap: DEFAULT-HASHMAP-3840-2
-- 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(name) - OrderedIndex
uk$unique(name) - UniqueHashIndex
-- 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.
For fully replicated tables, ndb_desc shows only the nodes holding primary partition fragment replicas; nodes with copy fragment replicas (only) are ignored. Beginning with NDB 7.5.4, you can obtain such information, using the mysql client, from the table_distribution_status
, table_fragments
, table_info
, and table_replicas
tables in the ndbinfo
database.
The following table includes options that are specific to ndb_desc. Additional descriptions follow the table. For options common to most NDB Cluster programs (including ndb_desc), see Section 21.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.
Table 21.246 Command-line options for the ndb_desc program
Format | Description | Added, Deprecated, or Removed |
---|---|---|
Show next value for AUTO_INCREMENT oolumn if table has one | ADDED: NDB 7.6.14 |
|
Include partition information for BLOB tables in output. Requires that the -p option also be used | (Supported in all MySQL 5.7 based releases) |
|
Show extra information for table such as database, schema, name, internal ID | ADDED: NDB 7.6.14 |
|
Name of database containing table | (Supported in all MySQL 5.7 based releases) |
|
Include partition-to-data-node mappings in output. Requires that the -p option also be used | (Supported in all MySQL 5.7 based releases) |
|
Display information about partitions | (Supported in all MySQL 5.7 based releases) |
|
Number of times to retry the connection (once per second) | (Supported in all MySQL 5.7 based releases) |
|
Specify the table in which to find an index. When this option is used, -p and -n have no effect and are ignored | (Supported in all MySQL 5.7 based releases) |
|
Use unqualified table names | (Supported in all MySQL 5.7 based releases) |
Show the next value for a table's
AUTO_INCREMENT
column, if it has one.Include information about subordinate
BLOB
andTEXT
columns.Use of this option also requires the use of the
--extra-partition-info
(-p
) option.Show additional contextual information for the table such as schema, database name, table name, and the table's internal ID.
Specify the database in which the table should be found.
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 NDB Cluster.
Use of this option also requires the use of the
--extra-partition-info
(-p
) option.Print additional information about the table's partitions.
Try to connect this many times before giving up. One connect attempt is made per second.
Specify the table in which to look for an index.
Use unqualified table names.
In NDB 7.5.3 and later, table indexes listed in the output are ordered by ID. Previously, this was not deterministic and could vary between platforms. (Bug #81763, Bug #23547742)