(mysql.info.gz) MySQL Cluster Limitations in 4

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 16.7 MySQL Cluster Limitations in 4.1
 =====================================
 
 Below is a list of known limitations with release 4.1 when comparing to
 the storage engines MyISAM and InnoDB. Currently there are no plans to
 address these in coming releases of 4.1 (but well in 5.0 or later
 releases).  At `http://bugs.mysql.com', category cluster, you fill find
 known bugs which are intended to be fixed in upcoming releases of 4.1
 (if marked 4.1).  This list is intended to be complete with respect to
 the above, please report discrepancies at `http://bugs.mysql.com',
 category cluster. If this discrepancy will not be fixed in 4.1 it will
 be added to this list.
 
 Non compliance in syntax (resulting in error when running an existing application)
           Not all charsets and collations supported, see  MySQL
           Cluster news-4.1.6 for a list of       the ones supported.
 
           No prefix indexes (can only index complete fields)
 
           No text indexes
 
           No geometry type support
 
 Non compliance in limits/behavior (may result in error when running an existing application)
           No partial rollback of transactions on error. As a result,
           e.g. duplicate key error, will result       in a rollback of
           the whole transaction.
 
           A number of hard limits exist which are configurable, but
           available main memory in the       cluster sets limits. See
           complete list of configuration parameters        MySQL
           Cluster Config File. Most configuration parameters can be
           upgraded on-line.
                Database memory size and index memory size, `DataMemory'
                and `IndexMemory'             respectively.
 
                How large transactions can be performed is set with
                config parameter
                `MaxNoOfConcurrentOperations'             (bulk load,
                truncate table and alter table are handled specially by
                running              several transactions, and thus does
                not have this limitation)
 
                Different limits related to tables and indexes, e.g. max
                number of ordered indexes,
                `MaxNoOfOrderedIndexes' etc.
 
           Database names, table names and attribute names cannot be as
           long in       ndb tables as in other table handlers.
           Attribute names will be truncated to 31 characters,       and
           if they are not unique after truncation gives an error.
           Database name and table name       can be max a total of 122
           characters together.
 
           Max number of meta data objects is limited to 1600 (includes
           tables, system tables, indexes and BLOBs)
 
           Max number of attributes per table limited to 128
 
           Max row size of 8k (not including BLOBs)
 
           Max number of attributes in a key is 32
 
 Not supported features (no error, but not supported/enforced)
           Foreign key construct is ignored (same behavior as MyISAM)
 
           Savepoint and rollback to savepoint ignored (same behavior as
           MyISAM)
 
 Performance and limitations related
           Query cache disabled since it is not invalidated if update
           occurs on other MySQL server
 
           Query performance issues due to sequential access to storage
           engine       and relatively more expensive to do many range
           scans.
 
           Records in range statistic not supported, giving non-optimal
               query plans in some cases. Use constructs `USE INDEX' or
           `FORCE INDEX'       to work around non optimal query plans.
 
           Unique hash index (constructed with `USING HASH') cannot be
           used for accessing table       if NULL is given as part of
           the key.
 
 Missing features
           Only support for READ_COMMITTED isolation level       (InnoDB
           supports READ_COMMITTED, REPEATABLE_READ and SERIALIZABLE)
 
           No disk durable commit (are replicated, but no guarantee that
           logs are       flushed to disk at commit)
 
 Problems related to multiple MySQL servers (not related to MyISAM or InnoDB)
           Alter table not fully blocking when running multiple MySQL
           servers (no distributed table lock)
 
           MySQL Replication will not work right off if updates are done
           on several MySQL servers.        If a partitioning scheme of
           the database is done at the application level, and no
           transactions       takes place across these partitions, it
           will work.
 
 Cluster only related (not related to MyISAM or InnoDB)
           All machines in the cluster must use the same architecture;
           that       is, all machines hosting nodes must be either
           big-endian or       little-endian, and you cannot use a
           mixture of both. For example,       you cannot have a
           management node running on a PPC which directs       a server
           node that is running on an x86 machine. This restriction
           does not apply to machines simply running `mysql' clients
             that may be accessing the cluster.
 
           No on-line schema changes (no on-line alter table,       Ndb
           on-line create index not accessible)
 
           No on-line add/drop node
 
           When using multiple management servers one must give nodes an
           id explicitly in the       connect strings since the
           automatic allocation of node id's does not work across
           several management servers.
 
           When using multiple management servers one must take extreme
           care to have the same       configuration in all management
           servers.  No checks for this are performed.
 
           Max number of storage nodes 48
 
           Total max number of nodes 63 (MySQL Servers, storage nodes
           and management servers)
 
 

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