Related Documentation Download this Excerpt

5.3.8.2 NDB Cluster System Variables

This section provides detailed information about MySQL server system variables that are specific to NDB Cluster and the NDB storage engine. For system variables not specific to NDB Cluster, see Server System Variables. For general information on using system variables, see Using System Variables.

  • have_ndbcluster

    Table 5.198 Type and value information for have_ndbcluster

    Property Value
    Name have_ndbcluster
    Command Line No
    System Variable Yes
    Option File No
    Scope Global
    Dynamic No
    Type: Default, Range boolean: (Version: 5.5)
    Notes

    DESCRIPTION: Whether mysqld supports NDB Cluster tables (set by --ndbcluster option)


    YES if mysqld supports NDBCLUSTER tables. DISABLED if --skip-ndbcluster is used.

    This variable is deprecated and is removed in MySQL 5.6. Use SHOW ENGINES instead.

  • ndb_autoincrement_prefetch_sz

    Property Value
    Command-Line Format --ndb-autoincrement-prefetch-sz=#
    System Variable ndb_autoincrement_prefetch_sz
    Scope Global, Session
    Dynamic Yes
    Type Integer
    Default Value 1
    Minimum Value 1
    Maximum Value 65536

    Determines the probability of gaps in an autoincremented column. Set it to 1 to minimize this. Setting it to a high value for optimization makes inserts faster, but decreases the likelihood that consecutive autoincrement numbers will be used in a batch of inserts.

    This variable affects only the number of AUTO_INCREMENT IDs that are fetched between statements; within a given statement, at least 32 IDs are obtained at a time.

    Important

    This variable does not affect inserts performed using INSERT ... SELECT.

  • ndb_cache_check_time

    Property Value
    Command-Line Format --ndb-cache-check-time=#
    System Variable ndb_cache_check_time
    Scope Global
    Dynamic Yes
    Type Integer
    Default Value 0

    The number of milliseconds that elapse between checks of NDB Cluster SQL nodes by the MySQL query cache. Setting this to 0 (the default and minimum value) means that the query cache checks for validation on every query.

    The recommended maximum value for this variable is 1000, which means that the check is performed once per second. A larger value means that the check is performed and possibly invalidated due to updates on different SQL nodes less often. It is generally not desirable to set this to a value greater than 2000.

  • ndb_deferred_constraints

    Property Value
    Command-Line Format --ndb-deferred-constraints=#
    System Variable ndb_deferred_constraints
    Scope Global, Session
    Dynamic Yes
    Type Integer
    Default Value 0
    Minimum Value 0
    Maximum Value 1

    Controls whether or not constraint checks are deferred, where these are supported. 0 is the default.

    This variable is not normally needed for operation of NDB Cluster or NDB Cluster Replication, and is intended primarily for use in testing.

  • ndb_distribution

    Property Value
    Command-Line Format --ndb-distribution={KEYHASH|LINHASH}
    System Variable ndb_distribution
    Scope Global
    Dynamic Yes
    Type Enumeration
    Default Value KEYHASH
    Valid Values

    LINHASH

    KEYHASH

    Controls the default distribution method for NDB tables. Can be set to either of KEYHASH (key hashing) or LINHASH (linear hashing). KEYHASH is the default.

  • ndb_eventbuffer_max_alloc

    Property Value
    Command-Line Format --ndb-eventbuffer-max-alloc=#
    Introduced 5.5.34-ndb-7.2.14
    System Variable ndb_eventbuffer_max_alloc
    Scope Global
    Dynamic Yes
    Type Integer
    Default Value 0
    Minimum Value 0
    Maximum Value 4294967295

    Sets the maximum amount memory (in bytes) that can be allocated for buffering events by the NDB API. 0 means that no limit is imposed, and is the default.

    This variable was added in NDB 7.2.14.

  • ndb_extra_logging

    Property Value
    Command-Line Format ndb_extra_logging=#
    System Variable ndb_extra_logging
    Scope Global
    Dynamic Yes
    Type Integer
    Default Value 1

    This variable enables recording in the MySQL error log of information specific to the NDB storage engine.

    When this variable is set to 0, the only information specific to NDB that is written to the MySQL error log relates to transaction handling. If it set to a value greater than 0 but less than 10, NDB table schema and connection events are also logged, as well as whether or not conflict resolution is in use, and other NDB errors and information. If the value is set to 10 or more, information about NDB internals, such as the progress of data distribution among cluster nodes, is also written to the MySQL error log. The default is 1.

  • ndb_force_send

    Property Value
    Command-Line Format --ndb-force-send[={OFF|ON}]
    System Variable ndb_force_send
    Scope Global, Session
    Dynamic Yes
    Type Boolean
    Default Value ON

    Forces sending of buffers to NDB immediately, without waiting for other threads. Defaults to ON.

  • ndb_index_stat_cache_entries

    Property Value
    Command-Line Format --ndb-index-stat-cache-entries=#
    Deprecated Yes (removed in 5.5.36-ndb-7.2.16)
    System Variable ndb_index_stat_cache_entries
    Scope Global, Session
    Dynamic Yes
    Type Integer
    Default Value 32
    Minimum Value 0
    Maximum Value 4294967295

    Sets the granularity of the statistics by determining the number of starting and ending keys to store in the statistics memory cache. Zero means no caching takes place; in this case, the data nodes are always queried directly. Default value: 32.

    Note

    If ndb_index_stat_enable is OFF, then setting this variable has no effect.

    This variable was deprecated in MySQL 5.1, and is removed from NDB 7.2.16 and later.

  • ndb_index_stat_enable

    Property Value
    Command-Line Format --ndb-index-stat-enable[={OFF|ON}]
    System Variable ndb_index_stat_enable
    Scope Global, Session
    Dynamic Yes
    Type Boolean
    Default Value ON

    Use NDB index statistics in query optimization. ON is the default in NDB Cluster 7.2 and later.

  • ndb_index_stat_option

    Property Value
    Command-Line Format --ndb-index-stat-option=value
    Introduced 5.5.15-ndb-7.2.1
    System Variable ndb_index_stat_option
    Scope Global, Session
    Dynamic Yes
    Type String
    Default Value loop_checkon=1000ms,loop_idle=1000ms,loop_busy=100ms, update_batch=1,read_batch=4,idle_batch=32,check_batch=32, check_delay=1m,delete_batch=8,clean_delay=0,error_batch=4, error_delay=1m,evict_batch=8,evict_delay=1m,cache_limit=32M, cache_lowpct=90

    This variable is used for providing tuning options for NDB index statistics generation. The list consist of comma-separated name-value pairs of option names and values. Note that this list must not contain any space characters.

    Options not used when setting ndb_index_stat_option are not changed from their default values. For example, you can set ndb_index_stat_option = 'loop_idle=1000ms,cache_limit=32M'.

    Time values can be optionally suffixed with h (hours), m (minutes), or s (seconds). Millisecond values can optionally be specified using ms; millisecond values cannot be specified using h, m, or s.) Integer values can be suffixed with K, M, or G.

    The names of the options that can be set using this variable are shown in the table that follows. The table also provides brief descriptions of the options, their default values, and (where applicable) their minimum and maximum values.

    Table 5.199 ndb_index_stat_option options and values

    Name Description Default/Units Minimum/Maximum
    loop_enable 1000 ms 0/4G
    loop_idle Time to sleep when idle 1000 ms 0/4G
    loop_busy Time to sleep when more work is waiting 100 ms 0/4G
    update_batch 1 0/4G
    read_batch 4 1/4G
    idle_batch 32 1/4G
    check_batch 8 1/4G
    check_delay How often to check for new statistics 10 m 1/4G
    delete_batch 8 0/4G
    clean_delay 1 m 0/4G
    error_batch 4 1/4G
    error_delay 1 m 1/4G
    evict_batch 8 1/4G
    evict_delay Clean LRU cache, from read time 1 m 0/4G
    cache_limit Maximum amount of memory in bytes used for cached index statistics by this mysqld; clean up the cache when this is exceeded. 32 M 0/4G
    cache_lowpct 90 0/100
    zero_total Setting this to 1 resets all accumulating counters in ndb_index_stat_status to 0. This option value is also reset to 0 when this is done. 0 0/1

  • ndb_index_stat_update_freq

    Property Value
    Command-Line Format --ndb-index-stat-update-freq=#
    Deprecated Yes (removed in 5.5.36-ndb-7.2.16)
    System Variable ndb_index_stat_update_freq
    Scope Global, Session
    Dynamic Yes
    Type Integer
    Default Value 20
    Minimum Value 0
    Maximum Value 4294967295

    How often to query data nodes instead of the statistics cache. For example, a value of 20 (the default) means to direct every 20th query to the data nodes.

    Note

    If ndb_index_stat_cache_entries is 0, then setting this variable has no effect; in this case, every query is sent directly to the data nodes.

    This variable was deprecated in MySQL 5.1, and is removed from NDB 7.2.16 and later.

  • ndb_join_pushdown

    Property Value
    System Variable ndb_join_pushdown
    Scope Global, Session
    Dynamic Yes
    Type Boolean
    Default Value ON

    Added in NDB 7.2.0, this variable controls whether joins on NDB tables are pushed down to the NDB kernel (data nodes). Previously, a join was handled using multiple accesses of NDB by the SQL node; however, when ndb_join_pushdown is enabled, a pushable join is sent in its entirety to the data nodes, where it can be distributed among the data nodes and executed in parallel on multiple copies of the data, with a single, merged result being returned to mysqld. This can reduce greatly the number of round trips between an SQL node and the data nodes required to handle such a join.

    By default, ndb_join_pushdown is enabled.

    Conditions for NDB pushdown joins.  In order for a join to be pushable, it must meet the following conditions:

    1. Only columns can be compared, and all columns to be joined must use exactly the same data type.

      This means that expressions such as t1.a = t2.a + constant cannot be pushed down, and that (for example) a join on an INT column and a BIGINT column also cannot be pushed down.

    2. Queries referencing BLOB or TEXT columns are not supported.

    3. Explicit locking is not supported; however, the NDB storage engine's characteristic implicit row-based locking is enforced.

      This means that a join using FOR UPDATE cannot be pushed down.

    4. In order for a join to be pushed down, child tables in the join must be accessed using one of the ref, eq_ref, or  const access methods, or some combination of these methods.

      Outer joined child tables can only be pushed using eq_ref.

      If the root of the pushed join is an eq_ref or const, only child tables joined by eq_ref can be appended. (A table joined by ref is likely to become the root of another pushed join.)

      If the query optimizer decides on Using join cache for a candidate child table, that table cannot be pushed as a child. However, it may be the root of another set of pushed tables.

    5. Joins referencing tables explicitly partitioned by [LINEAR] HASH, LIST, or RANGE currently cannot be pushed down.

    You can see whether a given join can be pushed down by checking it with EXPLAIN; when the join can be pushed down, you can see references to the pushed join in the Extra column of the output, as shown in this example:

    mysql> EXPLAIN
        ->     SELECT e.first_name, e.last_name, t.title, d.dept_name
        ->         FROM employees e
        ->         JOIN dept_emp de ON e.emp_no=de.emp_no
        ->         JOIN departments d ON d.dept_no=de.dept_no
        ->         JOIN titles t ON e.emp_no=t.emp_no\G
    *************************** 1. row ***************************
               id: 1
      select_type: SIMPLE
            table: d
             type: ALL
    possible_keys: PRIMARY
              key: NULL
          key_len: NULL
              ref: NULL
             rows: 9
            Extra: Parent of 4 pushed join@1
    *************************** 2. row ***************************
               id: 1
      select_type: SIMPLE
            table: de
             type: ref
    possible_keys: PRIMARY,emp_no,dept_no
              key: dept_no
          key_len: 4
              ref: employees.d.dept_no
             rows: 5305
            Extra: Child of 'd' in pushed join@1
    *************************** 3. row ***************************
               id: 1
      select_type: SIMPLE
            table: e
             type: eq_ref
    possible_keys: PRIMARY
              key: PRIMARY
          key_len: 4
              ref: employees.de.emp_no
             rows: 1
            Extra: Child of 'de' in pushed join@1
    *************************** 4. row ***************************
               id: 1
      select_type: SIMPLE
            table: t
             type: ref
    possible_keys: PRIMARY,emp_no
              key: emp_no
          key_len: 4
              ref: employees.de.emp_no
             rows: 19
            Extra: Child of 'e' in pushed join@1
    4 rows in set (0.00 sec)
    Note

    If inner joined child tables are joined by ref, and the result is ordered or grouped by a sorted index, this index cannot provide sorted rows, which forces writing to a sorted tempfile.

    Two additional sources of information about pushed join performance are available:

    1. The status variables Ndb_pushed_queries_defined, Ndb_pushed_queries_dropped, Ndb_pushed_queries_executed, and Ndb_pushed_reads (all introduced in NDB 7.2.0).

    2. The counters in the ndbinfo.counters table that belong to the DBSPJ kernel block. (These counters and the DBSPJ block were also introduced in NDB 7.2.0). See Section 7.10.7, “The ndbinfo counters Table”, for information about these counters. See also The DBSPJ Block, in the NDB Cluster API Developer Guide.

  • ndb_log_apply_status

    Property Value
    Command-Line Format --ndb-log-apply-status[={OFF|ON}]
    System Variable ndb_log_apply_status
    Scope Global
    Dynamic No
    Type Boolean
    Default Value OFF

    A read-only variable which shows whether the server was started with the --ndb-log-apply-status option.

  • ndb_log_bin

    Property Value
    Command-Line Format --ndb-log-bin[={OFF|ON}]
    System Variable ndb_log_bin
    Scope Global, Session
    Dynamic Yes
    Type Boolean
    Default Value ON

    Causes updates to NDB tables to be written to the binary log. Setting this variable has no effect if binary logging is not already enabled for the server using log_bin. ndb_log_bin defaults to 1 (ON); normally, there is never any need to change this value in a production environment.

  • ndb_log_binlog_index

    Property Value
    Command-Line Format --ndb-log-binlog-index[={OFF|ON}]
    System Variable ndb_log_binlog_index
    Scope Global
    Dynamic Yes
    Type Boolean
    Default Value ON

    Causes a mapping of epochs to positions in the binary log to be inserted into the ndb_binlog_index table. Setting this variable has no effect if binary logging is not already enabled for the server using log_bin. (In addition, ndb_log_bin must not be disabled.) ndb_log_binlog_index defaults to 1 (ON); normally, there is never any need to change this value in a production environment.

  • ndb_log_empty_epochs

    Property Value
    Command-Line Format --ndb-log-empty-epochs[={OFF|ON}]
    System Variable ndb_log_empty_epochs
    Scope Global
    Dynamic Yes
    Type Boolean
    Default Value OFF

    When this variable is set to 0, epoch transactions with no changes are not written to the binary log, although a row is still written even for an empty epoch in ndb_binlog_index.

  • ndb_log_empty_update

    Property Value
    Command-Line Format --ndb-log-empty-update[={OFF|ON}]
    System Variable ndb_log_empty_update
    Scope Global
    Dynamic Yes
    Type Boolean
    Default Value OFF

    When this variable is set to ON (1), update transactions with no changes are written to the binary log, even when log_slave_updates is enabled.

  • ndb_log_orig

    Property Value
    Command-Line Format --ndb-log-orig[={OFF|ON}]
    System Variable ndb_log_orig
    Scope Global
    Dynamic No
    Type Boolean
    Default Value OFF

    Shows whether the originating server ID and epoch are logged in the ndb_binlog_index table. Set using the --ndb-log-orig server option.

  • ndb_log_transaction_id

    Property Value
    Introduced 5.5.15-ndb-7.2.1
    System Variable ndb_log_transaction_id
    Scope Global
    Dynamic No
    Type Boolean
    Default Value OFF

    This read-only, Boolean system variable shows whether a slave mysqld writes NDB transaction IDs in the binary log (required to use active-active NDB Cluster Replication with NDB$EPOCH_TRANS() conflict detection). To change the setting, use the --ndb-log-transaction-id option.

    ndb_log_transaction_id is available in NDB 7.2.1 and later. It is not supported in mainline MySQL Server 5.5.

    For more information, see Section 8.11, “NDB Cluster Replication Conflict Resolution”.

  • ndb_optimized_node_selection

    Property Value
    Command-Line Format --ndb-optimized-node-selection=#
    System Variable ndb_optimized_node_selection
    Scope Global
    Dynamic No
    Type Integer
    Default Value 3
    Minimum Value 0
    Maximum Value 3

    There are two forms of optimized node selection, described here:

    1. The SQL node uses promixity to determine the transaction coordinator; that is, the closest data node to the SQL node is chosen as the transaction coordinator. For this purpose, a data node having a shared memory connection with the SQL node is considered to be closest to the SQL node; the next closest (in order of decreasing proximity) are: TCP connection to localhost; SCI connection; TCP connection from a host other than localhost.

    2. The SQL thread uses distribution awareness to select the data node. That is, the data node housing the cluster partition accessed by the first statement of a given transaction is used as the transaction coordinator for the entire transaction. (This is effective only if the first statement of the transaction accesses no more than one cluster partition.)

    This option takes one of the integer values 0, 1, 2, or 3. 3 is the default. These values affect node selection as follows:

    • 0: Node selection is not optimized. Each data node is employed as the transaction coordinator 8 times before the SQL thread proceeds to the next data node.

    • 1: Proximity to the SQL node is used to determine the transaction coordinator.

    • 2: Distribution awareness is used to select the transaction coordinator. However, if the first statement of the transaction accesses more than one cluster partition, the SQL node reverts to the round-robin behavior seen when this option is set to 0.

    • 3: If distribution awareness can be employed to determine the transaction coordinator, then it is used; otherwise proximity is used to select the transaction coordinator. (This is the default behavior.)

    Proximity is determined as follows:

    1. Start with the value set for the Group parameter (default 55).

    2. For an API node sharing the same host with other API nodes, decrement the value by 1. Assuming the default value for Group, the effective value for data nodes on same host as the API node is 54, and for remote data nodes 55.

  • ndb_report_thresh_binlog_epoch_slip

    Property Value
    Command-Line Format --ndb-report-thresh-binlog-epoch-slip=#
    System Variable ndb_report_thresh_binlog_epoch_slip
    Scope Global
    Dynamic Yes
    Type Integer
    Default Value 3
    Minimum Value 0
    Maximum Value 256

    This is a threshold on the number of epochs to be behind before reporting binary log status. For example, a value of 3 (the default) means that if the difference between which epoch has been received from the storage nodes and which epoch has been applied to the binary log is 3 or more, a status message is sent to the cluster log.

  • ndb_report_thresh_binlog_mem_usage

    Property Value
    Command-Line Format --ndb-report-thresh-binlog-mem-usage=#
    System Variable ndb_report_thresh_binlog_mem_usage
    Scope Global
    Dynamic Yes
    Type Integer
    Default Value 10
    Minimum Value 0
    Maximum Value 10

    This is a threshold on the percentage of free memory remaining before reporting binary log status. For example, a value of 10 (the default) means that if the amount of available memory for receiving binary log data from the data nodes falls below 10%, a status message is sent to the cluster log.

  • ndb_table_no_logging

    Property Value
    System Variable ndb_table_no_logging
    Scope Session
    Dynamic Yes
    Type Boolean
    Default Value OFF

    When this variable is set to ON or 1, it causes NDB tables not to be checkpointed to disk. More specifically, this setting applies to tables which are created or altered using ENGINE NDB when ndb_table_no_logging is enabled, and continues to apply for the lifetime of the table, even if ndb_table_no_logging is later changed. Suppose that A, B, C, and D are tables that we create (and perhaps also alter), and that we also change the setting for ndb_table_no_logging as shown here:

    SET @@ndb_table_no_logging = 1;
    CREATE TABLE A ... ENGINE NDB;
    CREATE TABLE B ... ENGINE MYISAM;
    CREATE TABLE C ... ENGINE MYISAM;
    ALTER TABLE B ENGINE NDB;
    SET @@ndb_table_no_logging = 0;
    CREATE TABLE D ... ENGINE NDB;
    ALTER TABLE C ENGINE NDB;
    SET @@ndb_table_no_logging = 1;

    After the previous sequence of events, tables A and B are not checkpointed; A was created with ENGINE NDB and B was altered to use NDB, both while ndb_table_no_logging was enabled. However, tables C and D are logged; C was altered to use NDB and D was created using ENGINE NDB, both while ndb_table_no_logging was disabled. Setting ndb_table_no_logging back to 1 or ON does not cause table C or D to be checkpointed.

    Note

    ndb_table_no_logging has no effect on the creation of NDB table schema files; to suppress these, use ndb_table_temporary instead.

  • ndb_table_temporary

    Property Value
    System Variable ndb_table_temporary
    Scope Session
    Dynamic Yes
    Type Boolean
    Default Value OFF

    When set to ON or 1, this variable causes NDB tables not to be written to disk: This means that no table schema files are created, and that the tables are not logged.

    Note

    Setting this variable currently has no effect in NDB Cluster 7.0 and later. This is a known issue; see Bug #34036.

  • ndb_use_copying_alter_table

    Property Value
    System Variable ndb_use_copying_alter_table
    Scope Global, Session
    Dynamic No

    Forces NDB to use copying of tables in the event of problems with online ALTER TABLE operations. The default value is OFF.

  • ndb_use_exact_count

    Property Value
    System Variable ndb_use_exact_count
    Scope Global, Session
    Dynamic Yes
    Type Boolean
    Default Value OFF

    Forces NDB to use a count of records during SELECT COUNT(*) query planning to speed up this type of query. The default value is OFF, which allows for faster queries overall.

  • ndb_use_transactions

    Property Value
    Command-Line Format --ndb-use-transactions[={OFF|ON}]
    System Variable ndb_use_transactions
    Scope Global, Session
    Dynamic Yes
    Type Boolean
    Default Value ON

    You can disable NDB transaction support by setting this variable's values to OFF (not recommended). The default is ON.

  • ndb_version

    Property Value
    System Variable ndb_version
    Scope Global
    Dynamic No
    Type String
    Default Value

    NDB engine version, as a composite integer.

  • ndb_version_string

    Property Value
    System Variable ndb_version_string
    Scope Global
    Dynamic No
    Type String
    Default Value

    NDB engine version in ndb-x.y.z format.

  • server_id_bits

    Table 5.200 Type and value information for server_id_bits

    Property Value
    Name server_id_bits
    Command Line Yes
    System Variable Yes
    Option File Yes
    Scope Global
    Dynamic No
    Type: Default, Range integer: 32 / 7 - 32 (Version: 5.5)
    Notes

    DESCRIPTION: Sets the number of least significant bits in the server_id actually used for identifying the server, permitting NDB API applications to store application data in the most significant bits. server_id must be less than 2 to the power of this value.


    The effective value of server_id if the server was started with the --server-id-bits option set to a nondefault value.

    If the value of server_id greater than or equal to 2 to the power of server_id_bits, mysqld refuses to start.

    This system variable is supported only by NDB Cluster. server_id_bits is not supported by the standard MySQL Server.

  • slave_allow_batching

    Table 5.201 Type and value information for slave_allow_batching

    Property Value
    Name slave_allow_batching
    Command Line Yes
    System Variable Yes
    Option File Yes
    Scope Global
    Dynamic Yes
    Type: Default, Range boolean: OFF (Version: 5.5)
    Notes

    DESCRIPTION: Turns update batching on and off for a replication slave


    Whether or not batched updates are enabled on NDB Cluster replication slaves.

    This variable is available for mysqld only as supplied with NDB Cluster or built from the NDB Cluster sources. For more information, see Section 8.6, “Starting NDB Cluster Replication (Single Replication Channel)”.

    Setting this variable had no effect in NDB Cluster 7.2 prior to NDB 7.2.10. (Bug #15953730)

  • transaction_allow_batching

    Table 5.202 Type and value information for transaction_allow_batching

    Property Value
    Name transaction_allow_batching
    Command Line No
    System Variable Yes
    Option File No
    Scope Session
    Dynamic Yes
    Type: Default, Range boolean: OFF (Version: 5.5)
    Notes

    DESCRIPTION: Allows batching of statements within a transaction. Disable AUTOCOMMIT to use.


    When set to 1 or ON, this variable enables batching of statements within the same transaction. To use this variable, autocommit must first be disabled by setting it to 0 or OFF; otherwise, setting transaction_allow_batching has no effect.

    It is safe to use this variable with transactions that performs writes only, as having it enabled can lead to reads from the before image. You should ensure that any pending transactions are committed (using an explicit COMMIT if desired) before issuing a SELECT.

    Important

    transaction_allow_batching should not be used whenever there is the possibility that the effects of a given statement depend on the outcome of a previous statement within the same transaction.

    This variable is currently supported for NDB Cluster only.

    Important

    Due an issue in the NDB Cluster 7.2 codebase (Bug #64697) prior to General Availability, this variable is not available prior to NDB 7.2.6.

The system variables in the following list all relate to the ndbinfo information database.

  • ndbinfo_database

    Table 5.203 Type and value information for ndbinfo_database

    Property Value
    Name ndbinfo_database
    Command Line No
    System Variable Yes
    Option File No
    Scope Global
    Dynamic No
    Type: Default, Range string: ndbinfo (Version: 5.5)
    Notes

    DESCRIPTION: The name used for the NDB information database; read only


    Shows the name used for the NDB information database; the default is ndbinfo. This is a read-only variable whose value is determined at compile time; you can set it by starting the server using --ndbinfo-database=name, which sets the value shown for this variable but does not actually change the name used for the NDB information database.

  • ndbinfo_max_bytes

    Table 5.204 Type and value information for ndbinfo_max_bytes

    Property Value
    Name ndbinfo_max_bytes
    Command Line Yes
    System Variable Yes
    Option File No
    Scope Both
    Dynamic Yes
    Type: Default, Range integer: 0 / - (Version: 5.5)
    Notes

    DESCRIPTION: Used for debugging only


    Used in testing and debugging only.

  • ndbinfo_max_rows

    Table 5.205 Type and value information for ndbinfo_max_rows

    Property Value
    Name ndbinfo_max_rows
    Command Line Yes
    System Variable Yes
    Option File No
    Scope Both
    Dynamic Yes
    Type: Default, Range integer: 10 / - (Version: 5.5)
    Notes

    DESCRIPTION: Used for debugging only


    Used in testing and debugging only.

  • ndbinfo_offline

    Table 5.206 Type and value information for ndbinfo_offline

    Property Value
    Name ndbinfo_offline
    Command Line No
    System Variable Yes
    Option File No
    Scope Global
    Dynamic Yes
    Type: Default, Range boolean: OFF (Version: 5.5)
    Notes

    DESCRIPTION: Put the ndbinfo database into offline mode, in which no rows are returned from tables or views


    Place the ndbinfo database into offline mode, in which tables and views can be opened even when they do not actually exist, or when they exist but have different definitions in NDB. No rows are returned from such tables (or views).

  • ndbinfo_show_hidden

    Table 5.207 Type and value information for ndbinfo_show_hidden

    Property Value
    Name ndbinfo_show_hidden
    Command Line Yes
    System Variable Yes
    Option File No
    Scope Both
    Dynamic Yes
    Type: Default, Range boolean: OFF (Version: 5.5)
    Notes

    DESCRIPTION: Whether to show ndbinfo internal base tables in the mysql client. The default is OFF.


    Whether or not the ndbinfo database's underlying internal tables are shown in the mysql client. The default is OFF.

  • ndbinfo_table_prefix

    Table 5.208 Type and value information for ndbinfo_table_prefix

    Property Value
    Name ndbinfo_table_prefix
    Command Line Yes
    System Variable Yes
    Option File No
    Scope Both
    Dynamic Yes
    Type: Default, Range string: ndb$ (Version: 5.5)
    Notes

    DESCRIPTION: The prefix to use for naming ndbinfo internal base tables


    The prefix used in naming the ndbinfo database's base tables (normally hidden, unless exposed by setting ndbinfo_show_hidden). This is a read-only variable whose default value is ndb$. You can start the server with the --ndbinfo-table-prefix option, but this merely sets the variable and does not change the actual prefix used to name the hidden base tables; the prefix itself is determined at compile time.

  • ndbinfo_version

    Table 5.209 Type and value information for ndbinfo_version

    Property Value
    Name ndbinfo_version
    Command Line No
    System Variable Yes
    Option File No
    Scope Global
    Dynamic No
    Type: Default, Range string: (Version: 5.5)
    Notes

    DESCRIPTION: The version of the ndbinfo engine; read only


    Shows the version of the ndbinfo engine in use; read-only.