A filter with id – How to solve this Elasticsearch error

Overview

A filter in Elasticsearch is all about applying some conditions inside the query that are used to narrow down the matching result set.

What it is used for

When a query is executed, Elasticsearch by default calculates the relevance score of the matching documents. But in some conditions it does not require scores to be calculated, for instance if a document falls in the range of two given timestamps. For all these Yes/No criteria, a filter clause is used.

Examples

Return all the results of a given index that falls between a date range:

GET my_index/_search
{
  "query": {
    "bool": {
      "filter": {
        "range": {
          "created_at": {
            "gte": "2020-01-01",
            "lte": "2020-01-10"
          }
        }
      }
    }
  }
}

Notes

• Queries are used to find out how relevant a document is to a particular query by calculating a score for each document, whereas filters are used to match certain criteria and are cacheable to enable faster execution.
• Filters do not contribute to scoring and thus are faster to execute.
• There are major changes introduced in Elasticsearch version 2.x onward related to how query and filters are written and performed internally.

Common problems

• The most common problem with filters is incorrect use inside the query. If filters are not used correctly, query performance can be significantly affected. So filters must be used wherever there is scope of not calculating the score. 
• Another problem often arises when using date range filters, if “now” is used to represent the current time. It has to be noted that “now” is continuously changing the timestamp and thus Elasticsearch cannot use caching of the response since the data set will keep changing.

Overview

A plugin is used to enhance the core functionalities of Elasticsearch. Elasticsearch provides some core plugins as a part of their release installation. In addition to those core plugins, it is possible to write your own custom plugins as well. There are several community plugins available on GitHub for various use cases.

Examples

Get all of the instructions for the plugin:

sudo bin/elasticsearch-plugin -h

Installing the S3 plugin for storing Elasticsearch snapshots on S3:

sudo bin/elasticsearch-plugin install repository-s3

Removing a plugin:

sudo bin/elasticsearch-plugin remove repository-s3

Installing a plugin using the file’s path:

sudo bin/elasticsearch-plugin install file:///path/to/plugin.zip

Notes and good things to know

• Plugins are installed and removed using the elasticsearch-plugin script, which ships as a part of the Elasticsearch installation and can be found inside the bin/ directory of the Elasticsearch installation path.
• A plugin has to be installed on every node of the cluster and each of the nodes has to be restarted to make the plugin visible.
• You can also download the plugin manually and then install it using the elasticsearch-plugin install command, providing the file name/path of the plugin’s source file.
• When a plugin is removed, you will need to restart every Elasticsearch node in order to complete the removal process.

Common issues

• Managing permission issues during and after plugin installation is the most common problem. If Elasticsearch was installed using the DEB or RPM packages then the plugin has to be installed using the root user. Otherwise you can install the plugin as the user that owns all of the Elasticsearch files.
• In the case of DEB or RPM package installation, it is important to check the permissions of the plugins directory after you install it. You can update the permission if it has been modified using the following command:

chown -R elasticsearch:elasticsearch path_to_plugin_directory 

• If your Elasticsearch nodes are running in a private subnet without internet access, you cannot install a plugin directly. In this case, you can simply download the plugins and copy the files inside the plugins directory of the Elasticsearch installation path on every node. The node has to be restarted in this case as well.