[JAY-787] Add the Prefix query to QueryBuilder

CHANGELOG.md

@@ -8,6 +8,13 @@ Please mark backwards incompatible changes with an exclamation mark at the start
 
 ## [Unreleased]
 
+### Added
+- The `JayAPI::Elasticsearch::QueryBuilder::QueryClauses::Prefix` class and the
+  corresponding `#prefix` method to the `MatchClauses` module. This allows the
+  use of Elasticsearch's
+  [prefix](https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-prefix-query.html)
+  query with the Query Builder.
+
 ## [29.9.0] - 2026-08-04
 
 ### Added

documentation/source/user_guidelines/elasticsearch/query_builder.rst

@@ -334,6 +334,18 @@ Example:
 
    query_builder.query.match_none
 
+prefix
+++++++
+
+A `Prefix Query`_ allows you to find documents in which one of the fields
+starts with the given prefix.
+
+Example:
+
+.. code-block:: ruby
+
+  query_builder.query.prefix(field: 'user.id', value: "ki")
+
 query_string
 ++++++++++++
 
@@ -539,6 +551,7 @@ Example:
 .. _`Match Phrase Query`: https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-match-query-phrase.html#query-dsl-match-query-phrase
 .. _`Match All`: https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-match-all-query.html
 .. _`Match None`: https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-match-all-query.html#query-dsl-match-none-query
+.. _`Prefix Query`: https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-prefix-query.html
 .. _`Query String Query`: https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-query-string-query.html
 .. _`Wildcard Query`: https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-wildcard-query.html
 .. _`Exists Query`: https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-exists-query.html

lib/jay_api/elasticsearch/query_builder/query_clauses/match_clauses.rb

@@ -5,6 +5,7 @@
 require_relative 'match_all'
 require_relative 'match_none'
 require_relative 'match_phrase'
+require_relative 'prefix'
 require_relative 'query_string'
 require_relative 'range'
 require_relative 'regexp'
@@ -31,6 +32,16 @@ def match_phrase(**params)
             self << ::JayAPI::Elasticsearch::QueryBuilder::QueryClauses::MatchPhrase.new(**params)
           end
 
+          # Adds a +JayAPI::Elasticsearch::QueryBuilder::QueryClauses::Prefix+
+          # clause to the Query Clauses set.
+          # @param [Hash] params The parameters for the +Prefix+ class.
+          # @return [self] Returns itself so that other methods can be chained.
+          # @raise [JayAPI::Elasticsearch::QueryBuilder::Errors::QueryBuilderError]
+          #   If an error occurs when trying to add the query clause to the set.
+          def prefix(**params)
+            self << ::JayAPI::Elasticsearch::QueryBuilder::QueryClauses::Prefix.new(**params)
+          end
+
           # Adds a +JayAPI::Elasticsearch::QueryBuilder::QueryClauses::QueryString+
           # clause to the Query Clauses set.
           # @param [Hash] params The parameters for the +QueryString+ class

lib/jay_api/elasticsearch/query_builder/query_clauses/prefix.rb

@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+require_relative 'query_clause'
+
+module JayAPI
+  module Elasticsearch
+    class QueryBuilder
+      class QueryClauses
+        # Represents a +Prefix+ query in Elasticsearch
+        # More information about this type of query can be found here:
+        # https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-prefix-query.html
+        class Prefix < ::JayAPI::Elasticsearch::QueryBuilder::QueryClauses::QueryClause
+          attr_reader :field, :value
+
+          # @param [String, Symbol] field The field where the prefix query
+          #   should be applied.
+          # @param [String] value The prefix to be found in +field+
+          def initialize(field:, value:)
+            super()
+            @field = field
+            @value = value
+          end
+
+          # @return [Hash] The Hash that represents this query (in
+          #   Elasticsearch's format)
+          def to_h
+            {
+              prefix: {
+                field => {
+                  value: value
+                }
+              }
+            }
+          end
+        end
+      end
+    end
+  end
+end

spec/jay_api/elasticsearch/query_builder/query_clauses/match_clauses_spec.rb

@@ -59,6 +59,16 @@ def <<(_clause)
     it_behaves_like '#match_phrase'
   end
 
+  describe '#prefix' do
+    subject(:method_call) { test_instance.prefix(**params) }
+
+    let(:params) { { field: 'test_case.name', value: 'Networking/CAN0' } }
+
+    let(:clause_class) { JayAPI::Elasticsearch::QueryBuilder::QueryClauses::Prefix }
+
+    it_behaves_like '#match_phrase'
+  end
+
   describe '#query_string' do
     subject(:method_call) { test_instance.query_string(**params) }
 

spec/jay_api/elasticsearch/query_builder/query_clauses/prefix_spec.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+require 'jay_api/elasticsearch/query_builder/query_clauses/prefix'
+
+RSpec.describe JayAPI::Elasticsearch::QueryBuilder::QueryClauses::Prefix do
+  let(:prefix) do
+    described_class.new(
+      field: 'user.id',
+      value: 'ki'
+    )
+  end
+
+  describe '#to_h' do
+    subject(:method_call) { prefix.to_h }
+
+    let(:expected_hash) do
+      {
+        prefix: {
+          'user.id' => {
+            value: 'ki'
+          }
+        }
+      }
+    end
+
+    it 'returns the expected hash' do
+      expect(method_call).to eq(expected_hash)
+    end
+  end
+end