ndb_desc 提供一个或多个 NDB 表的详细描述。ndb_desc provides a detailed description of one or more NDB tables.

用法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

在本节后面列出了可与 ndb_desc 一起使用的其他选项。Additional options that can be used with ndb_desc are listed later in this section.

示例输出Sample Output

MySQL 表的创建和填充语句：MySQL table creation and population statements:

USE test;

CREATE TABLE fish (
    id INT NOT NULL AUTO_INCREMENT,
    name VARCHAR(20) NOT NULL,
    length_mm INT NOT NULL,
    weight_gm INT 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);

ndb_desc 的输出：Output from ndb_desc:

$> ./ndb_desc -c localhost fish -d test -p
-- fish --
Version: 2
Fragment type: HashMapPartition
K Value: 6
Min load factor: 78
Max load factor: 80
Temporary table: no
Number of attributes: 4
Number of primary keys: 1
Length of frm data: 337
Max Rows: 0
Row Checksum: 1
Row GCI: 1
SingleUserMode: 0
ForceVarPart: 1
PartitionCount: 2
FragmentCount: 2
PartitionBalance: FOR_RP_BY_LDM
ExtraRowGciBits: 0
ExtraRowAuthorBits: 0
TableStatus: Retrieved
Table options:
HashMap: DEFAULT-HASHMAP-3840-2
-- Attributes --
id Int PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY AUTO_INCR
name Varchar(20;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY DYNAMIC
length_mm Int NOT NULL AT=FIXED ST=MEMORY DYNAMIC
weight_gm Int NOT NULL AT=FIXED ST=MEMORY DYNAMIC
-- Indexes --
PRIMARY KEY(id) - UniqueHashIndex
PRIMARY(id) - OrderedIndex
uk(name) - OrderedIndex
uk$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

可以在一次调用 ndb_desc 时，通过使用表名（以空格分隔）来获取多个表的信息。所有表必须位于同一个数据库中。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.

您可以使用 --table（简写：-t）选项，并将索引名称作为第一个参数提供给 ndb_desc，从而获取特定索引的更多信息，如下所示: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:

$> ./ndb_desc uk -d test -t fish
-- uk --
Version: 2
Base table: fish
Number of attributes: 1
Logging: 0
Index type: OrderedIndex
Index status: Retrieved
-- Attributes --
name Varchar(20;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
-- IndexTable 10/uk --
Version: 2
Fragment type: FragUndefined
K Value: 6
Min load factor: 78
Max load factor: 80
Temporary table: yes
Number of attributes: 2
Number of primary keys: 1
Length of frm data: 0
Max Rows: 0
Row Checksum: 1
Row GCI: 1
SingleUserMode: 2
ForceVarPart: 0
PartitionCount: 2
FragmentCount: 2
FragmentCountType: ONE_PER_LDM_PER_NODE
ExtraRowGciBits: 0
ExtraRowAuthorBits: 0
TableStatus: Retrieved
Table options:
-- Attributes --
name Varchar(20;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
NDB$TNODE Unsigned [64] PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY
-- Indexes --
PRIMARY KEY(NDB$TNODE) - UniqueHashIndex

当以这种方式指定索引时，--extra-partition-info 和 --extra-node-info 选项无效。When an index is specified in this way, the --extra-partition-info and --extra-node-info options have no effect.

输出中的 Version 列包含表的模式对象版本。有关如何解释此值的信息，请参阅 NDB 模式对象版本。The Version column in the output contains the table's schema object version. For information about interpreting this value, see NDB Schema Object Versions.

通过嵌入在CREATE TABLE和ALTER TABLE语句中的NDB_TABLE注释可以设置的三个表属性，也可以在ndb_desc输出中看到。表的FRAGMENT_COUNT_TYPE始终显示在FragmentCountType列中。READ_ONLY和FULLY_REPLICATED如果设置为 1，则显示在Table options列中。执行以下ALTER TABLE语句后，在mysql客户端中可以看到这些信息：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)

发出此警告是因为 READ_ONLY=1 需要该表的分片计数类型为（或设置为）ONE_PER_LDM_PER_NODE_GROUP；在这种情况下，NDB 会自动设置。您可以使用 ALTER TABLE 来检查 SHOW CREATE TABLE 语句是否达到了预期效果：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=utf8mb4 COLLATE=utf8mb4_0900_ai_ci
COMMENT='NDB_TABLE=READ_BACKUP=1,FULLY_REPLICATED=1'
1 row in set (0.01 sec)

由于 FRAGMENT_COUNT_TYPE 没有被显式设置，其值不会显示在 SHOW CREATE TABLE 打印的注释文本中。ndb_desc 仍会显示此属性的更新值。Table options 列显示刚刚启用的二进制属性。你可以在这里显示的输出中看到这一点（强调的文本）：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):

$> ./ndb_desc -c localhost fish -d test -p
-- fish --
Version: 4
Fragment type: HashMapPartition
K Value: 6
Min load factor: 78
Max load factor: 80
Temporary table: no
Number of attributes: 4
Number of primary keys: 1
Length of frm data: 380
Max Rows: 0
Row Checksum: 1
Row GCI: 1
SingleUserMode: 0
ForceVarPart: 1
PartitionCount: 1
FragmentCount: 1
FragmentCountType: ONE_PER_LDM_PER_NODE_GROUP
ExtraRowGciBits: 0
ExtraRowAuthorBits: 0
TableStatus: Retrieved
Table options: readbackup, fullyreplicated
HashMap: DEFAULT-HASHMAP-3840-1
-- Attributes --
id Int PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY AUTO_INCR
name Varchar(20;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY DYNAMIC
length_mm Int NOT NULL AT=FIXED ST=MEMORY DYNAMIC
weight_gm Int NOT NULL AT=FIXED ST=MEMORY DYNAMIC
-- Indexes --
PRIMARY KEY(id) - UniqueHashIndex
PRIMARY(id) - OrderedIndex
uk(name) - OrderedIndex
uk$unique(name) - UniqueHashIndex
-- Per partition info --
Partition       Row count       Commit count    Frag fixed memory       Frag varsized memory    Extent_space    Free extent_space

关于这些表属性的更多信息，请参见 第 15.1.20.12 节，“设置 NDB 注释选项”。For more information about these table properties, see Section 15.1.20.12, “Setting NDB Comment Options”.

列 Extent_space 和 Free extent_space 仅适用于具有磁盘列的 NDB 表；对于仅包含内存列的表，这些列始终包含值 0。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.

为说明它们的使用，我们修改之前的示例。首先，我们必须创建必要的磁盘数据对象，如下所示：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;

（有关刚刚显示的语句及其创建的对象的更多信息，请参见第 25.6.11.1 节，“NDB 集群磁盘数据对象”，以及第 15.1.16 节，“CREATE LOGFILE GROUP 语句”，和第 15.1.21 节，“CREATE TABLESPACE 语句”。）(For more information on the statements just shown and the objects created by them, see Section 25.6.11.1, “NDB Cluster Disk Data Objects”, as well as Section 15.1.16, “CREATE LOGFILE GROUP Statement”, and Section 15.1.21, “CREATE TABLESPACE Statement”.)

现在我们可以创建并填充一个fish表的版本，该版本将其两列存储在磁盘上（如果表的先前版本已经存在，则先删除它）：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):

DROP TABLE IF EXISTS fish;

CREATE TABLE fish (
    id INT NOT NULL AUTO_INCREMENT,
    name VARCHAR(20) NOT NULL,
    length_mm INT NOT NULL,
    weight_gm INT 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);

当针对此版本的表运行时，ndb_desc 显示以下输出：When run against this version of the table, ndb_desc displays the following output:

$> ./ndb_desc -c localhost fish -d test -p
-- fish --
Version: 1
Fragment type: HashMapPartition
K Value: 6
Min load factor: 78
Max load factor: 80
Temporary table: no
Number of attributes: 4
Number of primary keys: 1
Length of frm data: 1001
Max Rows: 0
Row Checksum: 1
Row GCI: 1
SingleUserMode: 0
ForceVarPart: 1
PartitionCount: 2
FragmentCount: 2
PartitionBalance: FOR_RP_BY_LDM
ExtraRowGciBits: 0
ExtraRowAuthorBits: 0
TableStatus: Retrieved
Table options: readbackup
HashMap: DEFAULT-HASHMAP-3840-2
Tablespace id: 16
Tablespace: ts_1
-- Attributes --
id Int PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY AUTO_INCR
name Varchar(80;utf8mb4_0900_ai_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
length_mm Int NOT NULL AT=FIXED ST=DISK
weight_gm Int NOT NULL AT=FIXED ST=DISK
-- Indexes --
PRIMARY KEY(id) - UniqueHashIndex
PRIMARY(id) - OrderedIndex
uk(name) - OrderedIndex
uk$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

这意味着在每个分区上，为此表从表空间分配了 1048576 字节，其中 1044440 字节仍然可用于额外存储。换句话说，每个分区当前用于存储该表基于磁盘列的数据的字节数是 1048576 - 1044440 = 4136 字节。显示为 Free extent_space 的字节数仅可用于存储 fish 表的磁盘列数据；因此，当从信息模式 FILES 表中选择时，它不可见。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.

Tablespace id 和 Tablespace 也显示在磁盘表中。Tablespace id and Tablespace are also displayed for Disk Data tables.

对于完全复制的表，ndb_desc 仅显示保存主分区片段副本的节点；仅有副本片段的节点将被忽略。您可以使用 mysql 客户端，从 table_distribution_status、table_fragments、table_info 和 table_replicas 表在 ndbinfo 数据库中获取此类信息。For fully replicated tables, ndb_desc shows only the nodes holding primary partition fragment replicas; nodes with copy fragment replicas (only) are ignored. 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.

可以与 ndb_desc 一起使用的所有选项在下表中显示。表格之后还有附加说明。All options that can be used with ndb_desc are shown in the following table. Additional descriptions follow the table.

输出中列出的表索引按 ID 排序。Table indexes listed in the output are ordered by ID.