12:18 p.m.
Author: rareddy
Date: 2010-09-14 13:18:39 -0400 (Tue, 14 Sep 2010)
New Revision: 2570
Modified:
branches/7.1.x/documentation/reference/src/main/docbook/en-US/content/translators.xml
Log:
TEIID-1255: adding documentation about multi-source models.
Modified:
branches/7.1.x/documentation/reference/src/main/docbook/en-US/content/translators.xml
===================================================================
---
branches/7.1.x/documentation/reference/src/main/docbook/en-US/content/translators.xml 2010-09-14
15:17:27 UTC (rev 2569)
+++
branches/7.1.x/documentation/reference/src/main/docbook/en-US/content/translators.xml 2010-09-14
17:18:39 UTC (rev 2570)
@@ -815,4 +815,43 @@
</itemizedlist>
</section>
</section>
+<section>
+ <title>Multi-Source Models and VDB</title>
+ <para>When you have multiple instances of data that are using identical schema
(horizantal sharding), Teiid can help you
+ aggregate data accoss all the instances, using "multi-source" models. In
this scenario, instead of creating/importing a model for
+ every data source, user needs to define a one source model that represents the schema
and configure multiple data
+ "sources" underneath it. During runtime, when a query issued aginst this
model, the query engine analyzes
+ the information and gathers the required data from
+ all the sources configured and aggregates the results and provides in a single result
set.</para>
+
+ <para>To mark a model as "multi-source", the user needs to supply
property called "supports-multi-source-bindings", in the "vdb.xml"
file.
+ Also, the user need to define multiple sources. Here is code example showing single
model with multiple sources defined.</para>
+ <programlisting><![CDATA[
+<vdb name="vdbname" version="1">
+ <model visible="true" type="PHYSICAL"
name="Customers" path="/Test/Customers.xmi">
+ <property name="supports-multi-source-bindings"
value="true"/>
+ <source name="chicago" translator-name="oracle"
connection-jndi-name="chicago-customers"/>
+ <source name="newyork" translator-name="oracle"
connection-jndi-name="newyork-customers"/>
+ <source name="la" translator-name="oracle"
connection-jndi-name="la-customers"/>
+ </model>
+</vdb>
+ ]]></programlisting>
+ <para>In the above example, the VDB defined has single model called
"Customers", that has multiple sources, namely
+ chicago, newyork, la that define different instances of data. Every time a model is
marked as "multi-source", the
+ runtime engine adds a additional column called "SOURCE_NAME" to every table
in that model. This column maps to the
+ source's name from the XML. For example, in the above xml that would be
"chicago", "la", "newyork". Essentially then
+ user can write queries like</para>
+ <programlisting><![CDATA[
+ select * from table where SOURCE_NAME = 'newyork'
+ update table column=value where SOURCE_NAME='newyork'
+ delete from table where column = x and SOURCE_NAME='newyork'
+ ]]></programlisting>
+ <para>Note that when user do not supply the "SOURCE_NAME" in the
criteria, it applies to all the sources. Unfortunately
+ Teiid currently do not support INSERT, this planned for future releases. Another
useful feature along with this
+ feature is "partial results" to skip unavailble souces if they are
down.</para>
+ <note><para>Currenlty the tooling support for managing the multi-source
feature is limited, so if you need to use this feature
+ build the VDB as usual in the Teiid Designer and then edit the "vdb.xml"
file in the VDB archive using a Text editor to
+ add the addtional sources as defined above. Make sure that you also deploy a data
source for each source defined.</para></note>
+</section>
+
</chapter>
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