DOCSP-26438: use struct in distinct pg (#213)

* DOCSP-26438: use struct in distinct pg

* wording fix and add filter

Author: rustagir

source/fundamentals/crud/read-operations/distinct.txt

@@ -21,8 +21,17 @@ specified field across a single collection.
 Sample Data
 ~~~~~~~~~~~
 
-To run the examples in this guide, load the sample data into the
-``tea.ratings`` collection with the following
+The example in this guide uses the following ``Course`` struct as a model for documents
+in the ``courses`` collection:
+
+.. literalinclude:: /includes/fundamentals/code-snippets/CRUD/distinctValues.go
+   :start-after: start-course-struct
+   :end-before: end-course-struct
+   :language: go
+   :dedent:
+
+To run the example, load the sample data into the
+``db.courses`` collection with the following
 snippet:
 
 .. literalinclude:: /includes/fundamentals/code-snippets/CRUD/distinctValues.go
@@ -33,8 +42,10 @@ snippet:
 
 .. include:: /includes/fundamentals/automatic-db-coll-creation.rst
 
-Each document contains a rating for a type of tea that corresponds to
-the ``type`` and ``rating`` fields.
+Each document contains a description of a university course that
+includes the course title, department, and enrollment. These items
+correspond to the ``title``, ``department``, and ``enrollment`` fields
+in each document.
 
 Distinct
 --------
@@ -48,8 +59,8 @@ method:
 
 .. tip::
 
-   If you specify an empty query filter, the method matches all the
-   documents in a collection.
+   If you specify an empty query filter, the ``Distinct()`` method
+   searches for distinct values across all documents in a collection.
 
 Modify Behavior
 ~~~~~~~~~~~~~~~
@@ -80,32 +91,31 @@ with the following methods:
 Example
 ```````
 
-The following example matches all documents and prints the distinct values
-of the ``type`` field using the ``Distinct()`` method: 
+The following example matches documents with an ``enrollment`` field
+value less than ``50`` and prints the distinct values
+of the ``department`` field using the ``Distinct()`` method: 
 
 .. io-code-block::
    :copyable: true
 
    .. input::
       :language: go
 
-      results, err := coll.Distinct(context.TODO(), "type", bson.D{})
+      results, err := coll.Distinct(context.TODO(), "department", bson.D{{"enrollment", bson.D{{"$lt", 50}}}})
       if err != nil {
-         panic(err)
+          panic(err)
       }
-
+      
       for _, result := range results {
-         fmt.Println(result)
+          fmt.Println(result)
       }
 
    .. output::
       :language: none
       :visible: false
 
-      Earl Grey
-      Masala
-      Matcha
-      Oolong
+      Earth Science
+      English
 
 Additional Information
 ----------------------

source/includes/fundamentals/code-snippets/CRUD/distinctValues.go

@@ -11,6 +11,15 @@ import (
 	"go.mongodb.org/mongo-driver/mongo/options"
 )
 
+// start-course-struct
+type Course struct {
+	Title      string
+	Department string
+	Enrollment int32
+}
+
+// end-course-struct
+
 func main() {
 	var uri string
 	if uri = os.Getenv("DRIVER_REF_URI"); uri == "" {
@@ -27,31 +36,25 @@ func main() {
 		}
 	}()
 
-	client.Database("tea").Collection("ratings").Drop(context.TODO())
-
 	// begin insert docs
-	coll := client.Database("tea").Collection("ratings")
+	coll := client.Database("db").Collection("courses")
 	docs := []interface{}{
-		bson.D{{"type", "Masala"}, {"rating", 10}},
-		bson.D{{"type", "Matcha"}, {"rating", 7}},
-		bson.D{{"type", "Masala"}, {"rating", 4}},
-		bson.D{{"type", "Oolong"}, {"rating", 9}},
-		bson.D{{"type", "Matcha"}, {"rating", 5}},
-		bson.D{{"type", "Earl Grey"}, {"rating", 8}},
-		bson.D{{"type", "Oolong"}, {"rating", 3}},
-		bson.D{{"type", "Matcha"}, {"rating", 6}},
-		bson.D{{"type", "Earl Grey"}, {"rating", 4}},
+		Course{Title: "World Fiction", Department: "English", Enrollment: 35},
+		Course{Title: "Abstract Algebra", Department: "Mathematics", Enrollment: 60},
+		Course{Title: "Modern Poetry", Department: "English", Enrollment: 12},
+		Course{Title: "Plate Tectonics", Department: "Earth Science", Enrollment: 30},
 	}
 
 	result, err := coll.InsertMany(context.TODO(), docs)
+	//end insert docs
+
 	if err != nil {
 		panic(err)
 	}
 	fmt.Printf("Number of documents inserted: %d\n", len(result.InsertedIDs))
-	//end insert docs
 
 	// begin distinct
-	results, err := coll.Distinct(context.TODO(), "type", bson.D{})
+	results, err := coll.Distinct(context.TODO(), "department", bson.D{{"enrollment", bson.D{{"$lt", 50}}}})
 	if err != nil {
 		panic(err)
 	}