In this example of Solr filter query, we will discuss about how to implement filter queries functionality provided by Apache Solr. We will discuss how to use single and multiple filter queries to achieve the desired results. Also we will show the various filter query syntax offered by Solr and discuss the advantages of using one over other.
To demonstrate the filter query usage, we will create a core in Solr using basic configuration and index a sample file shipped along with Solr installation.
Our preferred environment for this example is solr-5.0.0. Before you begin the Solr installation make sure you have JDK installed and Java_Home is set appropriately.
1. Install Apache Solr
To begin with, lets download the latest version of Apache Solr from the following location:
http://lucene.apache.org/solr/downloads.html
Apache Solr has gone through various changes from 4.x.x to 5.0.0, so if you have a different version of Solr you need to download the 5.x.x. version to follow this example.
Once the Solr zip file is downloaded, unzip it into a folder. The extracted folder will look like the below:
The bin folder contains the scripts to start and stop the server. The example folder contains few example files. We will be using one of them to demonstrate how Solr indexes the data. The server folder contains the logs folder where all the Solr logs are written. It will be helpful to check the logs for any error during indexing. The solr folder under server holds different collection or core. The configuration and data for each of the core/ collection are stored in the respective core/ collection folder.
Apache Solr comes with an inbuilt Jetty server. But before we start the solr instance we must validate the JAVA_HOME is set on the machine.
We can start the server using the command line script. Lets go to the bin directory from the command prompt and issue the following command:
solr start
This will start the Solr server under the default port 8983.
We can now open the following URL in the browser and validate that our Solr instance is running. The specifics of solr admin tool is beyond the scope of the example.
http://localhost:8983/solr/
2. Configuring Apache Solr
In this section, we will show you how to configure the core/collection for a solr instance and how to define the fields. Apache Solr ships with an option called Schemaless mode. This option allow users to construct effective schema without manually editing the schema file. But for this example we will use the Schema configuration for understanding the internals of the Solr.
2.1 Creating a Core
When the Solr server is started in Standalone mode, the configuration is called core and when it is started in SolrCloud mode, the configuration is called Collection. In this example we will discuss about the standalone server and core. We will park the SolrCloud discussion for later time.
First, we need to create a Core for indexing the data. The Solr create command has the following options:
- -c <name> – Name of the core or collection to create (required).
- -d <confdir> – The configuration directory, useful in the SolrCloud mode.
- -n <configName> – The configuration name. This defaults to the same name as the core or collection.
- -p <port> – Port of a local Solr instance to send the create command to; by default the script tries to detect the port by looking for running Solr instances.
- -s <shards> – Number of shards to split a collection into, default is 1.
- -rf <replicas> – Number of copies of each document in the collection. The default is 1.
In this example we will use the -c parameter for core name and -d parameter for the configuration directory. For all other parameters we make use of default settings.
Now navigate the solr-5.0.0\bin folder in the command window and issue the following command:
solr create -c jcg -d basic_configs
We can see the following output in the command window.
Creating new core 'jcg' using command:
http://localhost:8983/solr/admin/cores?action=CREATE&name=jcg&instanceDir=jcg
{
"responseHeader":{
"status":0,
"QTime":663},
"core":"jcg"}
Now we navigate to the following URL and we can see jcg core being populated in the core selector. You can also see the statistics of the core.
http://localhost:8983/solr
2.2 Modify the schema.xml file
We need to modify the schema.xml file under the folder server\solr\jcg\conf to include the fields. We will use one of the example file “books.csv” shipped along with Solr installation for indexing. The file is located under the folder solr-5.0.0\example\exampledocs
Now we navigate to the folder server\solr directory. You will see a folder called jcg created. The sub-folders namelyconf and data have the core’s configuration and indexed data respectively.
Now edit the schema.xml file in the \server\solr\jcg\conf folder and add the following contents after the uniqueKey element.
schema.xml
<uniqueKey>id</uniqueKey> <!-- Fields added for books.csv load--> <field name="cat" type="text_general" indexed="true" stored="true"/> <field name="name" type="text_general" indexed="true" stored="true"/> <field name="price" type="tdouble" indexed="true" stored="true"/> <field name="inStock" type="boolean" indexed="true" stored="true"/> <field name="author" type="text_general" indexed="true" stored="true"/>
We have set the attribute indexed to true. This specifies the field is used for indexing and the record can be retrieved using the index. Setting the value to false will make the field only stored but can’t be queried with.
Also note we have another attribute called stored and set it to true. This specifies the field is stored and can be returned in the output. Setting this field to false will make the field only indexed and can’t be retrieved in output.
We have assigned the type for the fields present in the “books.csv” file here. The first field in the CSV file “id” is automatically taken care by the uniqueKey element of schema.xml file for indexing.
Since we have modified the configuration we have to stop and start the server. To do so, we need to issue the following command from bin directory through command line:
solr stop -all
The server will be stopped now. Now to start the server issue the following command from bin directory through command line:
solr start
3. Indexing the Data
Apache Solr comes with a Standalone Java program called the SimplePostTool. This program is packaged into JAR and available with the installation under the folder example\exampledocs.
Now we navigate to the example\exampledocs folder in the command prompt and type the following command. You will see a bunch of options to use the tool.
java -jar post.jar -h
The usage format in general is as follows:
Usage: java [SystemProperties] -jar post.jar [-h|-] [<file|folder|url|arg>
[<file|folder|url|arg>...]]
As we said earlier, we will index the data present in the “books.csv” file shipped with Solr installation. We will navigate to the solr-5.0.0\example\exampledocs in the command prompt and issue the following command.
java -Dtype=text/csv -Durl=http://localhost:8983/solr/jcg/update -jar post.jar books.csv
The SystemProperties used here are:
- -Dtype – the type of the data file.
- -Durl – URL for the jcg core.
The file “books.csv” will now be indexed and the command prompt will display the following output.
SimplePostTool version 5.0.0 Posting files to [base] url http://localhost:8983/solr/jcg/update using content- type text/csv... POSTing file books.csv to [base] 1 files indexed. COMMITting Solr index changes to http://localhost:8983/solr/jcg/update... Time spent: 0:00:00.647
4. Filter queries
Solr provides the following parameter to filter the queries. This parameter can be used with other common query parameters to achieve the desired output.
- fq – Applies a filter query to the search results.
The fq parameter defines a query that can be used to restrict the superset of documents that can be returned, without influencing score. The fq parameterized queries are cached independent of the main query. When the same filter is used in the subsequent queries its a cache hit and the data is returned quickly from the cache.
4.1 Single filter query
Let’s form a query to search for the keyword Game in the name field. Open the following URL in the browser. This query will fetch two records as shown in the screenshot.
http://localhost:8983/solr/jcg/select?q=name
We will modify the query to filter the result for the book’s price between 1.00 to 7.00. With the filter parameter we will get only a single record.
Open the following URL in the browser:
http://localhost:8983/solr/jcg/select?q=name:Game&fq=price:[1.00 TO 7.00]
4.2 Multiple filters
The fq parameter can be specified multiple times in a query. The documents will only be included in the result if they are in the intersection of the document sets resulting from each instance of the parameter. In the example below, only documents which are in price between 1.00 and 7.00 and also in stock will be returned.
Open the following URL in the browser.
http://localhost:8983/solr/jcg/select?q=name:The&fq=price:[1.00 TO 7.00]&fq=inStock:true
Since the cache works on individual parameters it is suggested to use multiple fq parameters for better caching.
5. Download the source code
This was an example of solr filter queries.
You can download the schema file of this example here: filter_schema
