MySQL :: MySQL 8.4 Reference Manual :: 25.5.14 ndb_index_stat

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MySQL 8.4 Reference Manual / ... / ndb_index_stat — NDB Index Statistics Utility

25.5.14 ndb_index_stat — NDB 索引统计实用程序

ndb_index_stat provides per-fragment statistical information about indexes on NDB tables. This includes cache version and age, number of index entries per partition, and memory consumption by indexes.

To obtain basic index statistics about a given NDB table, invoke ndb_index_stat as shown here, with the name of the table as the first argument and the name of the database containing this table specified immediately following it, using the --database (-d) option:

ndb_index_stat table -d database

In this example, we use ndb_index_stat to obtain such information about an NDB table named mytable in the test database:

$> ndb_index_stat -d test mytable
table:City index:PRIMARY fragCount:2
sampleVersion:3 loadTime:1399585986 sampleCount:1994 keyBytes:7976
query cache: valid:1 sampleCount:1994 totalBytes:27916
times in ms: save: 7.133 sort: 1.974 sort per sample: 0.000

sampleVersion is the version number of the cache from which the statistics data is taken. Running ndb_index_stat with the --update option causes sampleVersion to be incremented.

loadTime shows when the cache was last updated. This is expressed as seconds since the Unix Epoch.

sampleCount is the number of index entries found per partition. You can estimate the total number of entries by multiplying this by the number of fragments (shown as fragCount).

sampleCount can be compared with the cardinality of SHOW INDEX or INFORMATION_SCHEMA.STATISTICS, although the latter two provide a view of the table as a whole, while ndb_index_stat provides a per-fragment average.

keyBytes is the number of bytes used by the index. In this example, the primary key is an integer, which requires four bytes for each index, so keyBytes can be calculated in this case as shown here:

    keyBytes = sampleCount * (4 bytes per index) = 1994 * 4 = 7976

This information can also be obtained using the corresponding column definitions from INFORMATION_SCHEMA.COLUMNS (this requires a MySQL Server and a MySQL client application).

totalBytes is the total memory consumed by all indexes on the table, in bytes.

Timings shown in the preceding examples are specific to each invocation of ndb_index_stat.

The --verbose option provides some additional output, as shown here:

$> ndb_index_stat -d test mytable --verbose
random seed 1337010518
connected
loop 1 of 1
table:mytable index:PRIMARY fragCount:4
sampleVersion:2 loadTime:1336751773 sampleCount:0 keyBytes:0
read stats
query cache created
query cache: valid:1 sampleCount:0 totalBytes:0
times in ms: save: 20.766 sort: 0.001
disconnected

$>

If the output from the program is empty, this may indicate that no statistics yet exist. To force them to be created (or updated if they already exist), invoke ndb_index_stat with the --update option, or execute ANALYZE TABLE on the table in the mysql client.

The following table includes options that are specific to the NDB Cluster ndb_index_stat utility. Additional descriptions are listed following the table.

--character-sets-dir

Command-Line Format	`--character-sets-dir=path`

Directory containing character sets.

--connect-retries

Command-Line Format	`--connect-retries=#`
Type	Integer
Default Value	`12`
Minimum Value	`0`
Maximum Value	`12`

Number of times to retry connection before giving up.

--connect-retry-delay

Command-Line Format	`--connect-retry-delay=#`
Type	Integer
Default Value	`5`
Minimum Value	`0`
Maximum Value	`5`

Number of seconds to wait between attempts to contact management server.

--connect-string

Command-Line Format	`--connect-string=connection_string`
Type	String
Default Value	`[none]`

Same as --ndb-connectstring.

--core-file

Command-Line Format	`--core-file`

Write core file on error; used in debugging.

--database=name, -d name

Command-Line Format	`--database=name`
Type	String
Default Value	`[none]`
Minimum Value
Maximum Value

The name of the database that contains the table being queried.

--defaults-extra-file

Command-Line Format	`--defaults-extra-file=path`
Type	String
Default Value	`[none]`

Read given file after global files are read.

--defaults-file

Command-Line Format	`--defaults-file=path`
Type	String
Default Value	`[none]`

Read default options from given file only.

--defaults-group-suffix

Command-Line Format	`--defaults-group-suffix=string`
Type	String
Default Value	`[none]`

Also read groups with concat(group, suffix).

--delete

Command-Line Format	`--delete`

Delete the index statistics for the given table, stopping any auto-update that was previously configured.

--dump

Command-Line Format	`--dump`

Dump the contents of the query cache.

--help

Command-Line Format	`--help`

Display help text and exit.

--login-path

Command-Line Format	`--login-path=path`
Type	String
Default Value	`[none]`

Read given path from login file.

--no-login-paths

Command-Line Format	`--no-login-paths`

Skips reading options from the login path file.

--loops=#

Command-Line Format	`--loops=#`
Type	Numeric
Default Value	`0`
Minimum Value	`0`
Maximum Value	`MAX_INT`

Repeat commands this number of times (for use in testing).

--ndb-connectstring

Command-Line Format	`--ndb-connectstring=connection_string`
Type	String
Default Value	`[none]`

Set connection string for connecting to ndb_mgmd. Syntax: [nodeid=id;][host=]hostname[:port]. Overrides entries in NDB_CONNECTSTRING and my.cnf.

--ndb-mgm-tls

Command-Line Format	`--ndb-mgm-tls=level`
Type	Enumeration
Default Value	`relaxed`
Valid Values	`relaxed` `strict`

Sets the level of TLS support required to connect to the management server; one of relaxed or strict. relaxed (the default) means that a TLS connection is attempted, but success is not required; strict means that TLS is required to connect.

--ndb-mgmd-host

Command-Line Format	`--ndb-mgmd-host=connection_string`
Type	String
Default Value	`[none]`

Same as --ndb-connectstring.

--ndb-nodeid

Command-Line Format	`--ndb-nodeid=#`
Type	Integer
Default Value	`[none]`

Set node ID for this node, overriding any ID set by --ndb-connectstring.

--ndb-optimized-node-selection

Command-Line Format	`--ndb-optimized-node-selection`

Enable optimizations for selection of nodes for transactions. Enabled by default; use --skip-ndb-optimized-node-selection to disable.

--ndb-tls-search-path

Command-Line Format	`--ndb-tls-search-path=list`
Type	Path name
Default Value (Unix)	`$HOME/ndb-tls`
Default Value (Windows)	`$HOMEDIR/ndb-tls`

Specify a list of directories to search for a CA file. On Unix platforms, the directory names are separated by colons (:); on Windows systems, the semicolon character (;) is used as the separator. A directory reference may be relative or absolute; it may contain one or more environment variables, each denoted by a prefixed dollar sign ($), and expanded prior to use.

Searching begins with the leftmost named directory and proceeds from left to right until a file is found. An empty string denotes an empty search path, which causes all searches to fail. A string consisting of a single dot (.) indicates that the search path limited to the current working directory.

If no search path is supplied, the compiled-in default value is used. This value depends on the platform used: On Windows, this is \ndb-tls; on other platforms (including Linux), it is $HOME/ndb-tls. This can be overridden by compiling NDB Cluster using -DWITH_NDB_TLS_SEARCH_PATH.

--no-defaults

Command-Line Format	`--no-defaults`

Do not read default options from any option file other than login file.

--print-defaults

Command-Line Format	`--print-defaults`

Print program argument list and exit.

--query=#

Command-Line Format	`--query=#`
Type	Numeric
Default Value	`0`
Minimum Value	`0`
Maximum Value	`MAX_INT`

Perform random range queries on first key attribute (must be int unsigned).

--sys-drop

Command-Line Format	`--sys-drop`

Drop all statistics tables and events in the NDB kernel. This causes all statistics to be lost.

--sys-create

Command-Line Format	`--sys-create`

Create all statistics tables and events in the NDB kernel. This works only if none of them exist previously.

--sys-create-if-not-exist

Command-Line Format	`--sys-create-if-not-exist`

Create any NDB system statistics tables or events (or both) that do not already exist when the program is invoked.

--sys-create-if-not-valid

Command-Line Format	`--sys-create-if-not-valid`

Create any NDB system statistics tables or events that do not already exist, after dropping any that are invalid.

--sys-check

Command-Line Format	`--sys-check`

Verify that all required system statistics tables and events exist in the NDB kernel.

--sys-skip-tables

Command-Line Format	`--sys-skip-tables`

Do not apply any --sys-* options to any statistics tables.

--sys-skip-events

Command-Line Format	`--sys-skip-events`

Do not apply any --sys-* options to any events.

--update

Command-Line Format	`--update`

Update the index statistics for the given table, and restart any auto-update that was previously configured.

--usage

Command-Line Format	`--usage`

Display help text and exit; same as --help.

--verbose

Command-Line Format	`--verbose`

Turn on verbose output.

--version

Command-Line Format	`--version`

Display version information and exit.

ndb_index_stat system options. The following options are used to generate and update the statistics tables in the NDB kernel. None of these options can be mixed with statistics options (see ndb_index_stat statistics options).

ndb_index_stat statistics options. The options listed here are used to generate index statistics. They work with a given table and database. They cannot be mixed with system options (see ndb_index_stat system options).

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