![Apache Solr Tutorial](/apache_solr/images/apache-solr-mini-logo.jpg)
- Apache Solr Tutorial
- Apache Solr - Home
- Apache Solr - Overview
- Apache Solr - Search Engine Basics
- Apache Solr - Windows Environment
- Apache Solr - On Hadoop
- Apache Solr - Architecture
- Apache Solr - Terminology
- Apache Solr - Basic Commands
- Apache Solr - Core
- Apache Solr - Indexing Data
- Apache Solr - Adding Docs (XML)
- Apache Solr - Updating Data
- Apache Solr - Deleting Documents
- Apache Solr - Retrieving Data
- Apache Solr - Querying Data
- Apache Solr - Faceting
- Apache Solr Useful Resources
- Apache Solr - Quick Guide
- Apache Solr - Useful Resources
- Apache Solr - Discussion
Apache Solr - Core
A Solr Core is a running instance of a Lucene index that contains all the Solr configuration files required to use it. We need to create a Solr Core to perform operations like indexing and analyzing.
A Solr application may contain one or multiple cores. If necessary, two cores in a Solr application can communicate with each other.
Creating a Core
After installing and starting Solr, you can connect to the client (web interface) of Solr.
![Create Core](/apache_solr/images/create_core.jpg)
As highlighted in the following screenshot, initially there are no cores in Apache Solr. Now, we will see how to create a core in Solr.
Using create command
One way to create a core is to create a schema-less core using the create command, as shown below −
[Hadoop@localhost bin]$ ./Solr create -c Solr_sample
Here, we are trying to create a core named Solr_sample in Apache Solr. This command creates a core displaying the following message.
Copying configuration to new core instance directory: /home/Hadoop/Solr/server/Solr/Solr_sample Creating new core 'Solr_sample' using command: http://localhost:8983/Solr/admin/cores?action=CREATE&name=Solr_sample&instanceD ir = Solr_sample { "responseHeader":{ "status":0, "QTime":11550 }, "core":"Solr_sample" }
You can create multiple cores in Solr. On the left-hand side of the Solr Admin, you can see a core selector where you can select the newly created core, as shown in the following screenshot.
![Core Selector](/apache_solr/images/core_selector.jpg)
Using create_core command
Alternatively, you can create a core using the create_core command. This command has the following options −
–c core_name | Name of the core you wanted to create |
-p port_name | Port at which you want to create the core |
-d conf_dir | Configuration directory of the port |
Let’s see how you can use the create_core command. Here, we will try to create a core named my_core.
[Hadoop@localhost bin]$ ./Solr create_core -c my_core
On executing, the above command creates a core displaying the following message −
Copying configuration to new core instance directory: /home/Hadoop/Solr/server/Solr/my_core Creating new core 'my_core' using command: http://localhost:8983/Solr/admin/cores?action=CREATE&name=my_core&instanceD ir = my_core { "responseHeader":{ "status":0, "QTime":1346 }, "core":"my_core" }
Deleting a Core
You can delete a core using the delete command of Apache Solr. Let’s suppose we have a core named my_core in Solr, as shown in the following screenshot.
![Delete Core](/apache_solr/images/delete_core.jpg)
You can delete this core using the delete command by passing the name of the core to this command as follows −
[Hadoop@localhost bin]$ ./Solr delete -c my_core
On executing the above command, the specified core will be deleted displaying the following message.
Deleting core 'my_core' using command: http://localhost:8983/Solr/admin/cores?action=UNLOAD&core = my_core&deleteIndex = true&deleteDataDir = true&deleteInstanceDir = true { "responseHeader" :{ "status":0, "QTime":170 } }
You can open the web interface of Solr to verify whether the core has been deleted or not.
![Web Interface](/apache_solr/images/web_interface.jpg)