Solr tutorial

This document covers the basics of running Solr using an example schema, and some sample data.

To follow along with this tutorial, you will need...

1. Java 1.5 or greater. Some places you can get it are from Sun, IBM, or BEA.
   Running java -version at the command line should indicate a version number starting with 1.5.
2. A Solr release.
3. FireFox or Mozilla is the preferred browser to view the admin pages, as the current stylesheet doesn't look good on Internet Explorer.

Please run the browser showing this tutorial and the Solr server on the same machine so tutorial links will correctly point to your Solr server.

Begin by unziping the Solr release and changing your working directory to be the "example" directory. (Note that the base directory name may vary with the version of Solr downloaded.)

chrish@asimov:~solr$ ls
solr-nightly.zip
chrish@asimov:~solr$ unzip -q solr-nightly.zip
chrish@asimov:~solr$ cd solr-nightly/example/

Solr can run in any Java Servlet Container of your choice, but to simplify this tutorial, the example index includes a small installation of Jetty. In order to compile JSPs, this version of Jetty requires that you run "java" from a JDK, not from a JRE.

To launch Jetty with the Solr WAR, and the example configs, just run the start.jar ...

chrish@asimov:~/solr/example$ java -jar start.jar
1 [main] INFO org.mortbay.log - Logging to org.slf4j.impl.SimpleLogger@1f436f5 via org.mortbay.log.Slf4jLog
334 [main] INFO org.mortbay.log - Extract jar:file:/home/chrish/solr/example/webapps/solr.war!/ to /tmp/Jetty__solr/webapp
Feb 24, 2006 5:54:52 PM org.apache.solr.servlet.SolrServlet init
INFO: user.dir=/home/chrish/solr/example
Feb 24, 2006 5:54:52 PM org.apache.solr.core.SolrConfig <clinit>
INFO: Loaded Config solrconfig.xml

...

1656 [main] INFO org.mortbay.log - Started SelectChannelConnector @ 0.0.0.0:8983

This will start up the Jetty application server on port 8983, and use your terminal to display the logging information from Solr.

You can see that the Solr is running by loading http://localhost:8983/solr/admin/ in your web browser. This is the main starting point for Administering Solr.

Your Solr server is up and running, but it doesn't contain any data. You can modify a Solr index by POSTing XML Documents containing instructions to add (or update) documents, delete documents, commit pending adds and deletes, and optimize your index.

The exampledocs directory contains samples of the types of instructions Solr expects, as well as a java utility for posting them from the command line (a post.sh shell script is also available, but for this tutorial we'll use the cross-platform Java client).

To try this, open a new terminal window, enter the exampledocs directory, and run "java -jar post.jar" on some of the XML files in that directory, indicating the URL of the Solr server:

chrish@asimov:~/solr/example/exampledocs$ java -jar post.jar solr.xml monitor.xml 
SimplePostTool: version 1.2
SimplePostTool: WARNING: Make sure your XML documents are encoded in UTF-8, other encodings are not currently supported
SimplePostTool: POSTing files to http://localhost:8983/solr/update..
SimplePostTool: POSTing file solr.xml
SimplePostTool: POSTing file monitor.xml
SimplePostTool: COMMITting Solr index changes..

You have now indexed two documents in Solr, and committed these changes. You can now search for "solr" using the "Make a Query" interface on the Admin screen, and you should get one result. Clicking the "Search" button should take you to the following URL...

http://localhost:8983/solr/select/?stylesheet=&q=solr&version=2.1&start=0&rows=10&indent=on

You can index all of the sample data, using the following command (assuming your shell supports the *.xml notation):

chrish@asimov:~/solr/example/exampledocs$ java -jar post.jar *.xml
SimplePostTool: version 1.2
SimplePostTool: WARNING: Make sure your XML documents are encoded in UTF-8, other encodings are not currently supported
SimplePostTool: POSTing files to http://localhost:8983/solr/update..
SimplePostTool: POSTing file hd.xml
SimplePostTool: POSTing file ipod_other.xml
SimplePostTool: POSTing file ipod_video.xml
SimplePostTool: POSTing file mem.xml
SimplePostTool: POSTing file monitor.xml
SimplePostTool: POSTing file monitor2.xml
SimplePostTool: POSTing file mp500.xml
SimplePostTool: POSTing file sd500.xml
SimplePostTool: POSTing file solr.xml
SimplePostTool: POSTing file spellchecker.xml
SimplePostTool: POSTing file utf8-example.xml
SimplePostTool: POSTing file vidcard.xml
SimplePostTool: COMMITting Solr index changes..

...and now you can search for all sorts of things using the default Lucene QueryParser syntax...

• video
• name:video
• +video +price:[* TO 400]

You may have noticed that even though the file solr.xml has now been POSTed to the server twice, you still only get 1 result when searching for "solr". This is because the example schema.xml specifies a "uniqueKey" field called "id". Whenever you POST instructions to Solr to add a document with the same value for the uniqueKey as an existing document, it automaticaly replaces it for you. You can see that that has happened by looking at the values for numDocs and maxDoc in the "CORE" section of the statistics page...

http://localhost:8983/solr/admin/stats.jsp

numDoc should be 16 (because some of our 11 example XML files contain more than one <doc>), but maxDoc may be larger as the maxDoc count includes logically deleted documents that have not yet been removed from the index. You can re-post the sample XML files over and over again as much as you want and numDocs will never increase,because the new documents will constantly be replacing the old.

Go ahead and edit the existing XML files to change some of the data, and re-run the java -jar post.jar command, you'll see your changes reflected in subsequent searches.

Deleting Data

You can delete data by POSTing a delete command to the update URL and specifying the value of the document's unique key field, or a query that matches multiple documents (be careful with that one!). Since these commands are smaller, we will specify them right on the command line rather than reference an XML file.

Execute the following command to delete a document

java -Ddata=args -Dcommit=no -jar post.jar "<delete><id>SP2514N</id></delete>"

Now if you go to the statistics page and scroll down to the UPDATE_HANDLERS section and verify that "deletesPending : 1"

If you search for id:SP2514N it will still be found, because index changes are not visible until changes are flushed to disk, and a new searcher is opened. To cause this to happen, send a commit command to Solr (post.jar does this for you by default):

java -jar post.jar

Now re-execute the previous search and verify that no matching documents are found. Also revisit the statistics page and observe the changes in both the UPDATE_HANDLERS section and the CORE section.

Here is an example of using delete-by-query to delete anything with DDR in the name:

java -Ddata=args -jar post.jar "<delete><query>name:DDR</query></delete>"

Commit can be a very expensive operation so it's best to make many changes to an index in a batch and then send the commit command at the end. There is also an optimize command that does the same thing as commit, in addition to merging all index segments into a single segment, making it faster to search and causing any deleted documents to be removed. All of the update commands are documented here.

To continue with the tutorial, re-add any documents you may have deleted by going to the exampledocs directory and executing

java -jar post.jar *.xml

Searches are done via HTTP GET on the select URL with the query string in the q parameter. You can pass a number of optional request parameters to the request handler to control what information is returned. For example, you can use the "fl" parameter to control what stored fields are returned, and if the relevancy score is returned...

• q=video&fl=name,id (return only name and id fields)
• q=video&fl=name,id,score (return relevancy score as well)
• q=video&fl=*,score (return all stored fields, as well as relevancy score)
• q=video&sort=price desc&fl=name,id (add sort specification: sort by price descending)

Solr provides a query form within the web admin interface that allows setting the various request parameters and is useful when trying out or debugging queries.

Sorting

Solr provides a simple method to sort on one or more indexed fields. Use the 'sort' parameter to specify "field direction" pairs...

• q=video&sort=price desc
• q=video&sort=price asc
• q=video&sort=inStock asc, price desc

"score" can also be used as a field name when specifying a sort...

• q=video&sort=score desc
• q=video&sort=inStock asc, score desc

If no sort is specified, the default is score desc, the same as in the Lucene search APIs.

Text fields are typically indexed by breaking the field into words and applying various transformations such as lowercasing, removing plurals, or stemming to increase relevancy. The same text transformations are normally applied to any queries in order to match what is indexed.

Example queries demonstrating relevancy improving transformations:

• A search for power-shot matches PowerShot, and adata matches A-DATA due to the use of WordDelimiterFilter and LowerCaseFilter.
• A search for name:printers matches Printer, and features:recharging matches Rechargeable due to stemming with the EnglishPorterFilter.
• A search for "1 gigabyte" matches things with GB, and pixima matches Pixma due to use of a SynonymFilter.

The schema defines the fields in the index and what type of analysis is applied to them. The current schema your server is using may be accessed via the [SCHEMA] link on the admin page.

A full description of the analysis components, Analyzers, Tokenizers, and TokenFilters available for use is here.

Analysis Debugging

There is a handy analysis debugging page where you can see how a text value is broken down into words, and shows the resulting tokens after they pass through each filter in the chain.

This shows how "Canon PowerShot SD500" would be indexed as a value in the name field. Each row of the table shows the resulting tokens after having passed through the next TokenFilter in the Analyzer for the name field. Notice how both powershot and power, shot are indexed. Tokens generated at the same position are shown in the same column, in this case shot and powershot.

Selecting verbose output will show more details, such as the name of each analyzer component in the chain, token positions, and the start and end positions of the token in the original text.

Selecting highlight matches when both index and query values are provided will take the resulting terms from the query value and highlight all matches in the index value analysis.

Here is an example of stemming and stop-words at work.

Congratulations! You successfully ran a small Solr instance, added some documents, and made changes to the index. You learned about queries, text analysis, and the Solr admin interface. You're ready to start using Solr on your own project! Continue on with the following steps:

• Subscribe to the Solr mailing lists!
• Make a copy of the Solr example directory as a template for your project.
• Customize the schema and other config in solr/conf/ to meet your needs.

Have Fun, and we'll see you on the Solr mailing lists!