25.5.6 ndb_blob_tool — Check and Repair BLOB and TEXT columns of NDB Cluster Tables

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MySQL 8.4 Reference Manual Including MySQL NDB Cluster 8.4

25.5.6 ndb_blob_tool — Check and Repair BLOB and TEXT columns of NDB Cluster Tables

This tool can be used to check for and remove orphaned BLOB column parts from NDB tables, as well as to generate a file listing any orphaned parts. It is sometimes useful in diagnosing and repairing corrupted or damaged NDB tables containing BLOB or TEXT columns.

The basic syntax for ndb_blob_tool is shown here:

ndb_blob_tool [options] table [column, ...]

Unless you use the --help option, you must specify an action to be performed by including one or more of the options --check-orphans, --delete-orphans, or --dump-file. These options cause ndb_blob_tool to check for orphaned BLOB parts, remove any orphaned BLOB parts, and generate a dump file listing orphaned BLOB parts, respectively, and are described in more detail later in this section.

You must also specify the name of a table when invoking ndb_blob_tool. In addition, you can optionally follow the table name with the (comma-separated) names of one or more BLOB or TEXT columns from that table. If no columns are listed, the tool works on all of the table's BLOB and TEXT columns. If you need to specify a database, use the --database (-d) option.

The --verbose option provides additional information in the output about the tool's progress.

All options that can be used with ndb_mgmd are shown in the following table. Additional descriptions follow the table.

• --add-missing

For each inline part in NDB Cluster tables which has no corresponding BLOB part, write a dummy BLOB part of the required length, consisting of spaces. - --character-sets-dir

Directory containing character sets. - --check-missing

Check for inline parts in NDB Cluster tables which have no corresponding BLOB parts. - --check-orphans

Check for BLOB parts in NDB Cluster tables which have no corresponding inline parts. - --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=db_name, -d

Specify the database to find the table in. - --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-orphans

Remove BLOB parts from NDB Cluster tables which have no corresponding inline parts. - --dump-file=file

Writes a list of orphaned BLOB column parts to file. The information written to the file includes the table key and BLOB part number for each orphaned BLOB part. - --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. - --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. - --usage

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

Provide extra information in the tool's output regarding its progress. - --version

Display version information and exit.

Example

First we create an NDB table in the test database, using the CREATE TABLE statement shown here:

USE test;

CREATE TABLE btest (
    c0 BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
    c1 TEXT,
    c2 BLOB
)   ENGINE=NDB;

Then we insert a few rows into this table, using a series of statements similar to this one:

INSERT INTO btest VALUES (NULL, 'x', REPEAT('x', 1000));

When run with --check-orphans against this table, ndb_blob_tool generates the following output:

$> ndb_blob_tool --check-orphans --verbose -d test btest
connected
processing 2 blobs
processing blob #0 c1 NDB$BLOB_19_1
NDB$BLOB_19_1: nextResult: res=1
total parts: 0
orphan parts: 0
processing blob #1 c2 NDB$BLOB_19_2
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=1
total parts: 10
orphan parts: 0
disconnected

The tool reports that there are no NDB BLOB column parts associated with column c1, even though c1 is a TEXT column. This is due to the fact that, in an NDB table, only the first 256 bytes of a BLOB or TEXT column value are stored inline, and only the excess, if any, is stored separately; thus, if there are no values using more than 256 bytes in a given column of one of these types, no BLOB column parts are created by NDB for this column. See Section 13.7, “Data Type Storage Requirements”, for more information.