Hello Frazer.
Thank you very much.
I got it.
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2009/11/12 Frazer Clement <Frazer.Clement@stripped>
> Hi Moon's Father,
> a) When you subscribe to data change events occurring on a table, the Ndb
> data nodes internally track changes occurring on tables that you specify,
> and send these changes to your API node.
>
> b) There is no overhead for non-DML operations - e.g. read-only queries.
> - If you subscribe to a subset of columns in a table, only those columns
> are sent from the data node to the API.
>
> For situations where the number of arriving row events / second is high,
> you should attempt to ensure that your listening thread is not starved of
> CPU.
> - If the listening thread in the API lags too far behind the 'latest event'
> occurring on the cluster, the data nodes may disconnect your API node.
> - In extreme cases, the links from the data nodes to the Api node may
> become overloaded by event information, resulting in new operations
> involving the Api failing until the overload situation passes.
>
> As with most things cluster, best to prototype and measure.
> Frazer
>
>
> Moon's Father wrote:
>
>> We use MySQL NDB event API to monitor DB data change. But I have two
>> confusion to consult with us.
>>
>> a. How this mechanism works internally in mySQL?
>>
>> b. If an event is defined on some columns of a table and DML
>> operations is not quite often (say one update/delete/insert per minute),
>> when the table is populated with large amount of data (say 10 million
>> records), what’s the performance impact?
>>
>>
>> Any reply is appreciated.
>>
>>
>>
>
> --
> Frazer Clement, Software Engineer, MySQL Cluster Sun Microsystems -
> www.mysql.com
> Office: Edinburgh, UK
>
> Are you MySQL certified? www.mysql.com/certification
>
>
