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ndb_blob_tool − check and repair BLOB and TEXT columns of NDB Cluster tables


ndb_blob_tool options table [column, ...]


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 23.28. Command−line options used with the program ndb_blob_tool

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.

Directory containing character sets.

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

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

Number of times to retry connection before giving up.

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

Same as −−ndb−connectstring.

Write core file on error; used in debugging.

−−database=db_name, −d
Specify the database to find the table in.

Read given file after global files are read.

Read default options from given file only.

Also read groups with concat(group, suffix).

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

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.

Display help text and exit.

Read given path from login file.

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

Same as −−ndb−connectstring.

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

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

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

Print program argument list and exit.

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

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

Display version information and exit.


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

USE test;
c1 TEXT,

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:

$> ndb_blob_tool −−check−orphans −−verbose −d test btest
processing 2 blobs
processing blob #0 c1 NDB$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
NDBT_ProgramExit: 0 − OK

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 11.7, “Data Type Storage Requirements”, for more information.


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For more information, please refer to the MySQL Reference Manual, which may already be installed locally and which is also available online at http://dev.mysql.com/doc/.


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