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<html><!-- == $Id: //open/mondrian-release/3.0/doc/faq.html#2 $ == This software is subject to the terms of the Common Public License == Agreement, available at the following URL: == http://www.opensource.org/licenses/cpl.html. == Copyright (C) 2002-2007 Julian Hyde == All Rights Reserved. == You must accept the terms of that agreement to use this software. --><head> <link rel="stylesheet" type="text/css" href="stylesheet.css"/> <title>Pentaho Analysis Services: Mondrian FAQs</title></head><body><!-- doc2web start --><!-- page title --><div class="contentheading">Mondrian FAQs</div><!-- end page title --><!-- ########################## faq contents ############################# --><ol> <li><a href="#Applications">How do I use Mondrian in my application?</a></li> <li><a href="#API">Why doesn't Mondrian use a standard API?</a></li> <li><a href="#MDX_dialect">How does Mondrian's dialect of MDX differ from MSOLAP's?</a></li> <li><a href="#Extensiblity">How can Mondrian be extended?</a></li> <li><a href="#Scalability">Can Mondrian handle large datasets?</a></li> <li><a href="#Tracing">How do I enable tracing?</a></li> <li><a href="#logging">How do I enable logging?</a></li> <li><a href="#connect_string">What is the syntax of a Mondrian connect string?</a></li> <li><a href="#Roadmap">Where is Mondrian going in the future?</a></li> <li><a href="#Further_reading">Where can I find out more? (Further reading)</a></li> <li><a href="#Feedback">Mondrian is wonderful! How can I possibly thank you?</a></li> <li><a href="#Modeling">Modeling</a></li> <ol> <li><a href="#measures_not_stored_in_the_fact_table">Measures not in the fact table</a></li> <li><a href="#fact_table_based_upon_query">How can I define my fact table based on an arbitrary SQL statement?</a></li> <li><a href="#case_sensitive_table_names">Why can't Mondrian find my tables?</a></li> </ol> <li><a href="#Build_install">Build/install</a></li> <ol> <li><a href="#compilation_errors">I get compilation errors? Why is this?</a></li> </ol> <li><a href="#Performance">Performance</a></li> <ol> <li><a href="#cache_refresh">When I change the data in the RDBMS, the result doesn't change even if i refresh the browser. Why is this?</a></li> <li><a href="#Tuning_the_Aggregate_function">Tuning the Aggregate function</a></li> </ol></ol><!-- ####################################################### 1. How do I use Mondrian in my application? ########################################################## --><h3>1. How do I use Mondrian in my application?<a name="Applications"> </a></h3><p>There are several ways. If you have a fixed set of queries which you'd liketo display as HTML tables, use the tab library. <a href="../webapp/taglib.jsp">webapp/taglib.jsp</a> is an example of this.</p><p dir="ltr">The JPivot project (<a href="http://jpivot.sourceforge.net">http://jpivot.sourceforge.net</a>)is a JSP-based pivot table, and will allow you to dynamically explore a datasetover the web. It replaces the prototype pivot table <a href="../webapp/morph.jsp">webapp/morph.jsp</a>.</p><p>You could also build a pivot table in a client technology such as Swing.</p><!-- ####################################################### 2. Why doesn't Mondrian use a standard API? ########################################################## --><h3>2. Why doesn't Mondrian use a standard API?<a name="API"> </a></h3><p>Because there isn't one. MDX is a component of Microsoft's OLE DB for OLAPstandard which, as the name implies, only runs on Windows. Mondrian's API isfairly similar in flavor to ADO MD (ActiveX Data Objects for Multidimensional),a API which Microsoft built in order to make OLE DB for OLAP easier to use.</p><p>XML for Analysis is pretty much OLE DB for OLAP expressed in Web Servicesrather than COM, and therefore seems to offer a platform-neutral standard forOLAP, but take-up seems to be limited to vendors who supported OLE DB for OLAPalready.</p><p>The other OLAP vendors failed to reach consensus several years ago with theOLAP Council API, then moved onto the JSR-069 ('JOLAP') specification. Mondrian included a partial implementation of the JOLAP API for several years, but this was removed in mondrian-2.3.</p><p>During 2006, Julian Hyde started work, in collaboration with some other projects and companies, on a pragmatic open API for Java-based OLAP called<a href="http://www.olap4j.org">olap4j</a>.</p><!-- ####################################################################### 3. How does Mondrian's dialect of MDX differ from MSOLAP's? ########################################################################## --><h3>3. How does Mondrian's dialect of MDX differ from MSOLAP's?<a name="MDX_dialect"> </a></h3><p>See <a href="mdx.html">MDX language specification</a>.</p><p>Not very much.</p><ol> <li>The <code>StrToSet()</code> and <code>StrToTuple()</code> functions take an extra parameter.</li> <li>Parsing is case-sensitive.</li> <li>Pseudo-functions <code>Param()</code> and <code>ParamRef()</code> allow you to create parameterized MDX statements.</li></ol><!-- ############################################ 4. How can Mondrian be extended? ############################################### --><h3>4. How can Mondrian be extended?<a name="Extensiblity"> </a></h3><p><i>todo</i>: <a name="User_defined_functions">User-defined functions</a></p><p><i>todo</i>: Cell readers</p><p><i>todo</i>: Member readers</p><!-- ################################################## 5. Can Mondrian handle large datasets? ##################################################### --><h3>5. Can Mondrian handle large datasets?<a name="Scalability"> </a></h3><p>Yes, if your RDBMS can. We delegate the aggregation to the RDBMS, and if yourRDBMS happens to have materialized group by views created, your query will fly.And the next time you run the same or a similar query, that will really fly,because the results will be in the aggregation cache.</p><!-- ####################################### 6. How do I enable tracing? ########################################## --><h3>6. How do I enable tracing?<a name="Tracing"> </a></h3><p>To enable tracing, set <code>mondrian.trace.level</code> to 1 in <code>mondrian.properties</code>. You will see text and execution time of each SQLstatement, like this:</p><blockquote> <p><code>SqlMemberSource.getLevelMemberCount: executing sql [select count(*) as `c0` from (select distinct `store`.`store_country` as `c0` from `store` as `store`) as `foo`], 110 ms<br> SqlMemberSource.getMembers: executing sql [select distinct `store`.`store_sqft` as `c0` from `store` as `store` order by `store`.`store_sqft`], 50 ms</code></p></blockquote><p>Notes:</p><ul> <li>If you are running mondrian from the command-line, or via Ant, <code> mondrian.properties</code> should be in the current directory.</li> <li>If you are running in Tomcat, <code>mondrian.properties</code> should be in <i></i><code><i>TOMCAT_HOME</i>/bin</code>. Changes will only take effect when you re-start Tomcat. The output goes to the console from which you started Tomcat.</li></ul><!-- ####################################### 7. How do I enable logging? ########################################## --><h3>7. How do I enable logging?<a name="logging"> </a></h3><p>Mondrian uses the <a href="http://logging.apache.org/log4j/docs/">Apache Log4j logger</a>. To build, test, and run Mondrian requires a log4j.jar file. A log4j.jar file is provided as part of the Mondriandistribution. </p><p>Also provided is a log4j.properties file. Such a file is neededwhen running Mondrian in standalone mode (such as when running theMondrian junit tests or the CmdRunner utility).Generally, Mondrian is embedded in an application, such as a webserver, which may have theirown log4j.properties file or some other mechanism for setting log4j properties.In such cases, the user must use those for controlling Mondrian's logging.</p><p>Mondrian follows Apache's guidance on what type of information is loggedat what level:<ul><li><code>FATAL</code>: A very severe error event that will presumably lead the application to abort.</li><li><code>ERROR</code>: An error event that might still allow the application to continue running.</li><li><code>WARN</code>: A potentially harmful situation.</li><li><code>INFO</code>: An informational message that highlight the progress of the application at a coarse-grained level.</li><li><code>DEBUG</code>: A fine-grained informational event that is most useful to debug an application. </li></ul></p><p>It is recommended for general use that the Mondrian log level be set to<code>WARN</code>; arguably, its good to know when things are going South.</p><!-- ############################################################### 8. What is the syntax of a Mondrian connect string? ################################################################## --><h3>8. What is the syntax of a Mondrian connect string?<a name="connect_string"> </a></h3><p>The syntax of the connect string is described in the Javadoc for the method<a href="api/mondrian/rolap/RolapConnection.html#RolapConnection(mondrian.olap.Util.PropertyList,boolean)">mondrian.olap.DriverManager.getConnection(String connectString, boolean fresh)</a>.</p><!-- ##################################################### 9. Where is Mondrian going in the future? ######################################################## --><h3>9. Where is Mondrian going in the future?<a name="Roadmap"> </a></h3><ol> <li>Presentation layer (see <a href="http://sourceforge.net/projects/jpivot"> JPivot</a> for more details).</li> <li>Complete implementation of MDX (not all of the functions implemented yet)</li> <li>Tuning</li></ol><!-- ########################################## 10. Where can I find out more? ############################################# --><h3>10. Where can I find out more?<a name="Further_reading"> </a></h3><p><a href="http://www.amazon.com/exec/obidos/tg/detail/-/0471400467/ref=pd_bxgy_text_1/002-1268646-6661668?v=glance&s=books"><i>MDX Solutions with Microsoft SQL Server Analysis Services</i> by GeorgeSpofford</a> is the best book I have found on MDX. Despite the title, principlesit describes can be applied to any RDBMS.</p><p><a href="http://www.amazon.com/exec/obidos/tg/detail/-/0471400300/ref=pd_sim_books_4/002-1268646-6661668?v=glance&s=books"><i>OLAP Solutions: Building Multidimensional Information Systems</i>by Erik Thomsen</a> is a great overview of multidimensional databases, but doesnot deal with MDX.</p><p>The reference work on data warehousing is<a href="http://www.amazon.com/exec/obidos/tg/detail/-/0471200247/qid=1038277569/sr=1-2/ref=sr_1_2/002-1268646-6661668?v=glance&s=books"><i>The Data Warehouse Toolkit: The Complete Guide to Dimensional Modeling (SecondEdition)</i>, by Ralph Kimball, Margy Ross</a>. It covers the business processwell, but the focus is more on star schemas and ROLAP than OLAP.</p><p>The<a href="http://msdn.microsoft.com/library/en-us/olapdmad/agmdxbasics_04qg.asp">Microsoft Analysis Services online documentation</a> has excellent onlinedocumentation of MDX, including a<a href="http://msdn.microsoft.com/library/en-us/olapdmad/agmdxfunctions_9elw.asp">list of MDX functions</a>.</p><!-- #################################################################### 11. Mondrian is wonderful! How can I possibly thank you? ####################################################################### --><h3>11. Mondrian is wonderful! How can I possibly thank you?<a name="Feedback"> </a></h3><p>We'd <a href="mailto:jhyde@users.sourceforge.net">love to hear</a> what you liked and didn't like aboutit. If you can think of ways that Mondrian can be improved, roll up your sleevesand help make it better. If you use Mondrian in your application, considersharing your work so that everyone can use it.</p><!-- ########################## 12. Modeling ############################# --><h3>12. Modeling<a name="Modeling"> </a></h3><!-- ###################################################### 12.1 Measures not stored in the fact table #####⌨️ 快捷键说明
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