Merge pull request #1471 from redis/DOC-5150-js-vec-json-examples

DOC-5150 and DOC-5151 JavaScript and C# vector json examples

Author: andy-stark-redis

content/develop/clients/dotnet/vecsearch.md

@@ -32,7 +32,9 @@ In the example below, we use [Microsoft.ML](https://dotnet.microsoft.com/en-us/a
 to generate the vector embeddings to store and index with Redis Query Engine.
 We also show how to adapt the code to use
 [Azure OpenAI](https://learn.microsoft.com/en-us/azure/ai-services/openai/how-to/embeddings?tabs=csharp)
-for the embeddings.
+for the embeddings. The code is first demonstrated for hash documents with a
+separate section to explain the
+[differences with JSON documents](#differences-with-json-documents).
 
 ## Initialize
 
@@ -89,7 +91,6 @@ using Azure;
 using Azure.AI.OpenAI;
 ```
 
-
 ## Define a function to obtain the embedding model
 
 {{< note >}}Ignore this step if you are using an Azure OpenAI
@@ -154,7 +155,9 @@ array as a `byte` string. To simplify this, we declare a
 then encodes the returned `float` array as a `byte` string. If you are
 storing your documents as JSON objects instead of hashes, then you should
 use the `float` array for the embedding directly, without first converting
-it to a `byte` string.
+it to a `byte` string (see [Differences with JSON documents](#differences-with-json-documents)
+below).
+
 
 ```csharp
 static byte[] GetEmbedding(
@@ -414,6 +417,156 @@ As you would expect, the result for `doc:1` with the content text
 is the result that is most similar in meaning to the query text
 *"That is a happy person"*.
 
+## Differences with JSON documents
+
+Indexing JSON documents is similar to hash indexing, but there are some
+important differences. JSON allows much richer data modeling with nested fields, so
+you must supply a [path]({{< relref "/develop/data-types/json/path" >}}) in the schema
+to identify each field you want to index. However, you can declare a short alias for each
+of these paths to avoid typing it in full for
+every query. Also, you must specify `IndexType.JSON` with the `On()` option when you
+create the index.
+
+The code below shows these differences, but the index is otherwise very similar to
+the one created previously for hashes:
+
+```cs
+var jsonSchema = new Schema()
+    .AddTextField(new FieldName("$.content", "content"))
+    .AddTagField(new FieldName("$.genre", "genre"))
+    .AddVectorField(
+        new FieldName("$.embedding", "embedding"),
+        VectorField.VectorAlgo.HNSW,
+        new Dictionary<string, object>()
+        {
+            ["TYPE"] = "FLOAT32",
+            ["DIM"] = "150",
+            ["DISTANCE_METRIC"] = "L2"
+        }
+    );
+
+
+db.FT().Create(
+    "vector_json_idx",
+    new FTCreateParams()
+        .On(IndexDataType.JSON)
+        .Prefix("jdoc:"),
+    jsonSchema
+);
+```
+
+An important difference with JSON indexing is that the vectors are
+specified using arrays of `float` instead of binary strings. This requires a modification
+to the `GetEmbedding()` function declared in
+[Define a function to generate an embedding](#define-a-function-to-generate-an-embedding)
+above:
+
+```cs
+static float[] GetFloatEmbedding(
+    PredictionEngine<TextData, TransformedTextData> model, string sentence
+)
+{
+    // Call the prediction API to convert the text into embedding vector.
+    var data = new TextData()
+    {
+        Text = sentence
+    };
+
+    var prediction = model.Predict(data);
+
+    float[] floatArray = Array.ConvertAll(prediction.Features, x => (float)x);
+    return floatArray;
+}
+```
+
+You should make a similar modification to the `GetEmbeddingFromAzure()` function
+if you are using Azure OpenAI with JSON.
+
+Use [`JSON().set()`]({{< relref "/commands/json.set" >}}) to add the data
+instead of [`HashSet()`]({{< relref "/commands/hset" >}}):
+
+```cs
+var jSentence1 = "That is a very happy person";
+
+var jdoc1 = new {
+    content = jSentence1,
+    genre = "persons",
+    embedding = GetFloatEmbedding(predEngine, jSentence1),
+};
+
+db.JSON().Set("jdoc:1", "$", jdoc1);
+
+var jSentence2 = "That is a happy dog";
+
+var jdoc2 = new {
+    content = jSentence2,
+    genre = "pets",
+    embedding = GetFloatEmbedding(predEngine, jSentence2),
+};
+
+db.JSON().Set("jdoc:2", "$", jdoc2);
+
+var jSentence3 = "Today is a sunny day";
+
+var jdoc3 = new {
+    content = jSentence3,
+    genre = "weather",
+    embedding = GetFloatEmbedding(predEngine, jSentence3),
+};
+
+db.JSON().Set("jdoc:3", "$", jdoc3);
+```
+
+The query is almost identical to the one for the hash documents. This
+demonstrates how the right choice of aliases for the JSON paths can
+save you having to write complex queries. The only significant difference is
+that the `FieldName` objects created for the `ReturnFields()` option must
+include the JSON path for the field.
+
+An important thing to notice
+is that the vector parameter for the query is still specified as a
+binary string (using the `GetEmbedding()` method), even though the data for
+the `embedding` field of the JSON was specified as a `float` array.
+
+```cs
+var jRes = db.FT().Search("vector_json_idx",
+    new Query("*=>[KNN 3 @embedding $query_vec AS score]")
+    .AddParam("query_vec", GetEmbedding(predEngine, "That is a happy person"))
+    .ReturnFields(
+        new FieldName("$.content", "content"),
+        new FieldName("$.score", "score")
+    )
+    .SetSortBy("score")
+    .Dialect(2));
+
+foreach (var doc in jRes.Documents) {
+    var props = doc.GetProperties();
+    var propText = string.Join(
+        ", ",
+        props.Select(p => $"{p.Key}: '{p.Value}'")
+    );
+
+    Console.WriteLine(
+        $"ID: {doc.Id}, Properties: [\n  {propText}\n]"
+    );
+}
+```
+
+Apart from the `jdoc:` prefixes for the keys, the result from the JSON
+query is the same as for hash:
+
+```
+ID: jdoc:1, Properties: [
+  score: '4.30777168274', content: 'That is a very happy person'
+]
+ID: jdoc:2, Properties: [
+  score: '25.9752807617', content: 'That is a happy dog'
+]
+ID: jdoc:3, Properties: [
+  score: '68.8638000488', content: 'Today is a sunny day'
+]
+```
+
 ## Learn more
 
 See