{"id":24227,"date":"2023-03-31T16:12:48","date_gmt":"2023-03-31T14:12:48","guid":{"rendered":"https:\/\/www.dbi-services.com\/blog\/?p=24227"},"modified":"2023-03-31T16:19:57","modified_gmt":"2023-03-31T14:19:57","slug":"elasticsearch-is-case-sensitive-or-insensitive","status":"publish","type":"post","link":"https:\/\/www.dbi-services.com\/blog\/elasticsearch-is-case-sensitive-or-insensitive\/","title":{"rendered":"Elasticsearch: is case-sensitive or insensitive?"},"content":{"rendered":"\n

One more blog in the Elasticsearch series (blogs list at <\/strong>the bottom), this time we will try to learn more together about indexing and search, more specifically answer the question: is Elasticsearch case-sensitive or case-insensitive?<\/p>\n\n\n\n\n\n\n\n

To be honest, I had this question as a beginner and rapidly noticed that there are two sides to answer it. First the indexing, is it case-sensitive? How Elasticsearch behave to index a new document?<\/p>\n\n\n\n

Then, the search, is it case-sensitive? How Elasticsearch behave to find and select document(s)?<\/p>\n\n\n\n

Use case<\/h2>\n\n\n\n

Let’s first understand the default behavior, then we will see together how to adapt it to our need.<\/p>\n\n\n\n

I will take the same example as my previous blog<\/a>, I created the below document:<\/p>\n\n\n

\n{\n  "title": "Index data with Elastic",\n  "category": "User Stories",\n  "author": {\n    "first_name": "David",\n    "last_name": "Diab"\n  }\n}\n<\/pre><\/div>\n\n\n
Then, I searched for “Index” in the title field:<\/p>\n\n\n\n
\"\"<\/figure>\n\n\n\n
Let’s redo the same search but with “index” in lowercase, we get the same result:<\/p>\n\n\n\n
\"\"<\/figure>\n\n\n\n
Why?<\/p>\n\n\n\n
Indexing default behavior<\/h2>\n\n\n\n
Based on above example, indexing and searches seem to be case-insensitive! In fact, this is due to a process called text analysis which occurs when your string fields are indexed. At index time, text strings are analyzed, by default, text analysis breaks up a text string into individual words (tokens) and lowercase those words, e.g.:<\/p>\n\n\n
\n
\"\"<\/figure>\n<\/div>\n\n\n
Search default behavior<\/h2>\n\n\n\n
Your query string is analyzed too, it makes search case-insensitive by default. An example is more than welcome to better understand:<\/p>\n\n\n\n
\"\"<\/figure>\n\n\n\n
Please note that Elasticsearch calculates a score for each document found, which represent how relevant a document is in regards to the specific query. Elasticsearch uses BM25 as default scoring algorithm. We will discuss more about that in a next blog \ud83d\ude09<\/p>\n\n\n\n
How to change the default behavior?<\/h2>\n\n\n\n
Analyzers<\/strong><\/p>\n\n\n\n
Text analysis is done by an analyzer, by default, Elasticsearch applies the standard analyzer. But, there are many other analyzers: whitespace, stop, pattern, language-specific analyzers, and much more.<\/p>\n\n\n\n
In reality, the built-in analyzers work great for many use cases, but you may need to define your own custom analyzers which is possible with Elasticsearch.<\/p>\n\n\n\n
Text and Keyword<\/strong><\/p>\n\n\n\n
Text analysis is great for full text search, which enables you to search for individual words in a case-insensitive manner. But, we understood from the example that some strings do not need to be analyzed, instead of “united” and “states” as separate values, we probably want to search “United States” as it is…<\/p>\n\n\n\n
That is why Elasticsearch has two kinds of string data types:<\/p>\n\n\n\n