(mysql.info) mysql-5-0-cluster-changes

(mysql.info) mysql-cluster-roadmap
(mysql.info) mysql-5-1-cluster-roadmap
 
 15.9.1 MySQL Cluster Changes in MySQL 5.0
 -----------------------------------------
 
 MySQL Cluster in versions 5.0.3-beta and later contains a number of new
 features that are likely to be of interest:
 
    * *Push-Down Conditions*: Consider the following query:
 
           SELECT * FROM t1 WHERE non_indexed_attribute = 1;
 
      This query will use a full table scan and the condition will be
      evaluated in the cluster's data nodes. Thus, it is not necessary
      to send the records across the network for evaluation. (That is,
      function transport is used, rather than data transport.) Please
      note that this feature is currently disabled by default (pending
      more thorough testing), but it should work in most cases. This
      feature can be enabled through the use of the `SET
      engine_condition_pushdown = On' statement.  Alternatively, you can
      run `mysqld' with the this feature enabled by starting the MySQL
      server with the -engine-condition-pushdown option.
 
      A major benefit of this change is that queries can be executed in
      parallel. This means that queries against non-indexed columns can
      run faster than previously by a factor of as much as 5 to 10
      times, _times the number of data nodes_, because multiple CPUs can
      work on the query in parallel.
 
      You can use `EXPLAIN' to determine when condition pushdown is
      being used. See  explain.
 
    * *Decreased `IndexMemory' Usage*: In MySQL 5.0, each record
      consumes approximately 25 bytes of index memory, and every unique
      index uses 25 bytes per record of index memory (in addition to
      some data memory because these are stored in a separate table).
      This is because the primary key is not stored in the index memory
      anymore.
 
    * *Query Cache Enabled for MySQL Cluster*: See  query-cache,
      for information on configuring and using the query cache.
 
    * *New Optimizations*: One optimization that merits particular
      attention is that a batched read interface is now used in some
      queries. For example, consider the following query:
 
           SELECT * FROM t1 WHERE PRIMARY_KEY IN (1,2,3,4,5,6,7,8,9,10);
 
      This query will be executed 2 to 3 times more quickly than in
      previous MySQL Cluster versions due to the fact that all 10 key
      lookups are sent in a single batch rather than one at a time.
 
    * *Limit On Number of Metadata Objects*: In MySQL 4.1, each Cluster
      database may contain a maximum of 1600 metadataobjects, including
      database tables, system tables, indexes and BLOBs. Beginning with
      MySQL 5.0.6, this number is increased to 20320.
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