How to use Elasticsearch wildcard queries

Elasticsearch is a powerful search engine that allows users to efficiently search and retrieve data from large datasets. Elasticsearch comes bundled free with all our Managed Hosting plans.

One of the key features that Elasticsearch offers is the ability to perform wildcard queries. In this article, we will explore the basics of wildcard queries, their syntax, supported wildcard characters, and examine their importance in search operations.

Basics of wildcard queries

Wildcard queries are a type of search query that allows users to find documents based on patterns rather than exact matches.

This is particularly useful when searching for data that may have variations or uncertainties in certain fields.

At their core, wildcard queries use wildcard characters to represent unknown or variable parts of a query term.

The two most common wildcard characters are the asterisk (*) and the question mark (?). The asterisk (*) represents any number of characters (including zero), while the question mark (?) Represents exactly one character.

For example, a wildcard query for the term “cat*” will match documents containing words like “cat”, “cats”, “caterpillar”, and “category”. Similarly, a query for “ca?” will match documents containing words like “cat” and “car” but not “caterpillar” or “category”.

Supported wildcard characters

Elasticsearch supports a variety of wildcard characters that enable users to perform specific and flexible searches.

• The asterisk (*) represents zero or more characters.
• The question mark (?) Represents exactly one character.
• The tilde (~) allows for fuzzy matching, which matches terms that are similar but not exact.
• The square brackets ([]) allow for character ranges, such as [a-z] to match any single lowercase letter between ‘a’ and ‘z’.
• The curly braces ({}) allow for grouping multiple options together, for example, “ca{t,rs}” will match either “cat” or “cars”.

Wildcard queries can match documents in ways that may not be immediately obvious.

Therefore, it’s essential to understand the behaviour of each wildcard character and use them judiciously.

Use cases for wildcard queries

Wildcard queries have a wide range of use cases and can be valuable in various real-world scenarios.

One common application is in log analysis, where wildcard queries can help identify patterns or anomalies in log data.

For example, an it administrator may use wildcard queries to search for logs related to specific error codes, ip addresses, or user agents.

Wildcard queries are also widely used in e-commerce search engines to provide users with more flexible search options.

For instance, an online marketplace may allow customers to search for products using wildcard queries like “sweatsh*rts” to match variations like “sweatshirts” and “sweatshorts”.

In the healthcare industry, wildcard queries can be used to search for medical records based on incomplete or uncertain information. For example, a doctor may use wildcard queries to search for patient records with similar symptoms or test results.

Simple wildcard query examples

To better understand how wildcard queries work, let’s walk through some basic examples using the Elasticsearch query dsl (domain specific language).

Suppose we have an index of products and we want to find all products with a name starting with “apple”.

The wildcard query would look like this:

Get /products/_search{  "query": {    "wildcard": {      "name": "apple*"    }  }}

This query will return all products with names like “apple”, “applesauce”, and “applepie”.

We can also use wildcard queries to search for patterns or variations within a word. For example, if we want to find products with names like “shoe” or “shoes”, we can use a wildcard query like this:

Get /products/_search{  "query": {    "wildcard": {      "name": "shoe?"    }  }}

This query will match products with names like “shoe” and “shoes”, but not “shoese” or “shooes”.

Combining wildcard queries with other queries

Wildcard queries can be combined with other types of queries to create more complex search operations. This allows users to harness the power of Elasticsearch’s rich querying capabilities.

For example, we can combine a wildcard query with a term query to search for products with a specific attribute and a name that matches a pattern.

Here’s an example:

Get /products/_search{  "query": {    "bool": {      "must": [        {          "term": { "color": "red" }        },        {          "wildcard": { "name": "appl*" }        }      ]    }  }}

This query will find all red products with names that start with “appl”, such as “apple”, “applesauce”, and “application”.

Performance considerations

While wildcard queries offer powerful search capabilities, they can also impact search performance, especially when used on large datasets.

Be mindful of the potential performance implications and adopt optimization strategies where necessary.

To optimize wildcard queries, it’s recommended to:

• Use wildcard queries sparingly and only when necessary.
• Use more specific conditions or filters to narrow down the scope of the search before applying wildcard queries.
• Consider using other query types such as prefix queries or fuzzy queries when dealing with specific use cases.

Best practices for using wildcard queries

To ensure efficient and effective usage of wildcard queries, follow best practices and guidelines.

Here are some recommendations:

• Structure your queries to make them more readable and maintainable.
• Use a combination of wildcard queries with other query types to achieve the desired results.
• Experiment with different wildcard characters and variations to find the most accurate matches.
• Regularly monitor and optimize wildcard queries to ensure search performance remains optimal.

Handling large datasets

When dealing with large Elasticsearch indices, special considerations should be taken to ensure efficient wildcard querying.

Here are some strategies for handling large datasets:

• Utilize index partitioning techniques to divide data into smaller, more manageable chunks.
• Implement appropriate sharding and caching mechanisms to distribute query load across multiple nodes.
• Leverage Elasticsearch’s distributed nature to parallelize query execution and improve response times.

Security implications

Wildcard queries, if left unguarded, can pose security risks, especially in multi-user environments where unauthorized queries can expose sensitive or confidential information.

It is crucial to implement appropriate security measures to safeguard against unauthorized wildcard queries.

Some security recommendations include:

• Implementing access control measures to restrict wildcard query access to authorized users.
• Regularly monitoring logs and auditing wildcard query usage to detect and prevent misuse.
• Educating users about the potential risks associated with wildcard queries and promoting responsible query usage.

These security measures can minimize the chances of unauthorized wildcard queries compromising system security.

Advanced techniques and tips

For users looking to further enhance their wildcard querying capabilities, there are advanced techniques and tips worth exploring.

These techniques can improve search precision and relevance, resulting in more accurate and insightful search results.

Some advanced techniques and tips include:

• Utilizing regular expressions instead of wildcard queries to perform more complex pattern matching.
• Leveraging Elasticsearch’s scoring capabilities to prioritize more relevant search results.
• Employing advanced analyzers and tokenizers to handle language-specific wildcard queries.

Troubleshooting wildcard query issues

Like any complex search operation, wildcard queries may encounter issues or errors that need to be addressed. Here are some common wildcard query issues and solutions to help troubleshoot:

• Inaccurate matches: in some cases, wildcard queries may produce inaccurate matches or miss relevant documents. Adjusting the query or using other query types like fuzzy queries can help improve accuracy.
• Slow performance: when wildcard queries are slow, you can optimize query execution by following the performance considerations mentioned earlier. Additionally, tuning Elasticsearch’s performance settings can further enhance query speed.
• Syntax errors: incorrect syntax can lead to query failures. Reviewing the query syntax and ensuring proper formatting can help resolve syntax errors.

Final thoughts

Elasticsearch wildcard queries offer a flexible and powerful way to search for data based on patterns rather than exact matches.

By understanding the basics of wildcard queries, their syntax, and supported wildcard characters, users can leverage these capabilities to their advantage.

Throughout this guide, we have explored the importance of wildcard queries, their use cases, provided examples, and covered advanced techniques and troubleshooting tips.

It’s now your turn to experiment with wildcard queries in your own Elasticsearch deployments, unlocking the full potential of Elasticsearch’s search capabilities.