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.

Table 25.28 Command-line options used with the program ndb_blob_tool

Format	Description	Added, Deprecated, or Removed
--add-missing	Write dummy blob parts to take place of those which are missing	ADDED: NDB 8.0.20
--character-sets-dir=path	Directory containing character sets	REMOVED: 8.0.31
--check-missing	Check for blobs having inline parts but missing one or more parts from parts table	ADDED: NDB 8.0.20
--check-orphans	Check for blob parts having no corresponding inline parts	(Supported in all NDB releases based on MySQL 8.0)
--connect-retries=#	Number of times to retry connection before giving up	(Supported in all NDB releases based on MySQL 8.0)
--connect-retry-delay=#	Number of seconds to wait between attempts to contact management server	(Supported in all NDB releases based on MySQL 8.0)
--connect-string=connection_string, -c connection_string	Same as --ndb-connectstring	(Supported in all NDB releases based on MySQL 8.0)
--core-file	Write core file on error; used in debugging	REMOVED: 8.0.31
--database=name, -d name	Database to find the table in	(Supported in all NDB releases based on MySQL 8.0)
--defaults-extra-file=path	Read given file after global files are read	(Supported in all NDB releases based on MySQL 8.0)
--defaults-file=path	Read default options from given file only	(Supported in all NDB releases based on MySQL 8.0)
--defaults-group-suffix=string	Also read groups with concat(group, suffix)	(Supported in all NDB releases based on MySQL 8.0)
--delete-orphans	Delete blob parts having no corresponding inline parts	(Supported in all NDB releases based on MySQL 8.0)
--dump-file=file	Write orphan keys to specified file	(Supported in all NDB releases based on MySQL 8.0)
--help, -?	Display help text and exit	(Supported in all NDB releases based on MySQL 8.0)
--login-path=path	Read given path from login file	(Supported in all NDB releases based on MySQL 8.0)
--ndb-connectstring=connection_string, -c connection_string	Set connect string for connecting to ndb_mgmd. Syntax: "[nodeid=id;][host=]hostname[:port]". Overrides entries in NDB_CONNECTSTRING and my.cnf	(Supported in all NDB releases based on MySQL 8.0)
--ndb-mgmd-host=connection_string, -c connection_string	Same as --ndb-connectstring	(Supported in all NDB releases based on MySQL 8.0)
--ndb-nodeid=#	Set node ID for this node, overriding any ID set by --ndb-connectstring	(Supported in all NDB releases based on MySQL 8.0)
--ndb-optimized-node-selection	Enable optimizations for selection of nodes for transactions. Enabled by default; use --skip-ndb-optimized-node-selection to disable	REMOVED: 8.0.31
--no-defaults	Do not read default options from any option file other than login file	(Supported in all NDB releases based on MySQL 8.0)
--print-defaults	Print program argument list and exit	(Supported in all NDB releases based on MySQL 8.0)
--usage, -?	Display help text and exit; same as --help	(Supported in all NDB releases based on MySQL 8.0)
--verbose, -v	Verbose output	(Supported in all NDB releases based on MySQL 8.0)
--version, -V	Display version information and exit	(Supported in all NDB releases based on MySQL 8.0)

• --add-missing

  Command-Line Format	--add-missing
  Introduced	8.0.20-ndb-8.0.20

  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

  Command-Line Format	--character-sets-dir=path
  Removed	8.0.31

  Directory containing character sets.

• --check-missing

  Command-Line Format	--check-missing
  Introduced	8.0.20-ndb-8.0.20

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

• --check-orphans

  Command-Line Format	--check-orphans

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

• --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
  Removed	8.0.31

  Write core file on error; used in debugging.

• --database=db_name, -d

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

  Specify the database to find the table in.

• --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-orphans

  Command-Line Format	--delete-orphans

  Remove BLOB parts from NDB Cluster tables which have no corresponding inline parts.

• --dump-file=file

  Command-Line Format	--dump-file=file
  Type	File name
  Default Value	[none]

  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

  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.

• --ndb-connectstring

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

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

• --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
  Removed	8.0.31

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

• --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.

• --usage

  Command-Line Format	--usage

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

• --verbose

  Command-Line Format	--verbose

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

• --version

  Command-Line Format	--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.