25.5.14 ndb_index_stat — NDB Index Statistics Utility

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MySQL 8.4 Reference Manual Including MySQL NDB Cluster 8.4

25.5.14 ndb_index_stat — NDB Index Statistics Utility

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.

Usage

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.

Options

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

Directory containing character sets. - --connect-retries

Number of times to retry connection before giving up. - --connect-retry-delay

Number of seconds to wait between attempts to contact management server. - --connect-string

Same as --ndb-connectstring. - --core-file

Write core file on error; used in debugging. - --database=name, -d name

The name of the database that contains the table being queried. - --defaults-extra-file

Read given file after global files are read. - --defaults-file

Read default options from given file only. - --defaults-group-suffix

Also read groups with concat(group, suffix). - --delete

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

Dump the contents of the query cache. - --help

Display help text and exit. - --login-path

Read given path from login file. - --no-login-paths

Skips reading options from the login path file. - --loops=#

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

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

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

Same as --ndb-connectstring. - --ndb-nodeid

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

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

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

Print program argument list and exit. - --query=#

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

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

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

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

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

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

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

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

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

Turn on verbose output. - --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).

• --sys-drop
• --sys-create
• --sys-create-if-not-exist
• --sys-create-if-not-valid
• --sys-check
• --sys-skip-tables
• --sys-skip-events

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).

• --database
• --delete
• --update
• --dump
• --query