Add similarity module config in index resource (#321)

* Add similarity module config in index resource

Author: Jiahui Jiang

es/resource_elasticsearch_index.go

@@ -25,6 +25,7 @@ var (
 		"shard.check_on_startup",
 		"sort.field",
 		"sort.order",
+		"index.similarity.default",
 	}
 	dynamicsSettingsKeys = []string{
 		"number_of_replicas",
@@ -141,6 +142,13 @@ var (
 			ForceNew:    true,
 			Optional:    true,
 		},
+		"index_similarity_default": {
+			Type:         schema.TypeString,
+			Description:  "A JSON string describing the default index similarity config.",
+			Optional:     true,
+			ForceNew:     true, // To update index similarity config, the index must be closed, updated, and then reopened; we can't handle that here.
+			ValidateFunc: validation.StringIsJSON,
+		},
 		// Dynamic settings that can be changed at runtime
 		"number_of_replicas": {
 			Type:        schema.TypeString,
@@ -498,6 +506,17 @@ func resourceElasticsearchIndexCreate(d *schema.ResourceData, meta interface{})
 		body["mappings"] = mappings
 	}
 
+	// Decode index.similarity.default JSON
+	if defaultIndexSimilarityJSON, ok := d.GetOk("index_similarity_default"); ok {
+		var defaultIndexSimilarity map[string]interface{}
+		bytes := []byte(defaultIndexSimilarityJSON.(string))
+		err = json.Unmarshal(bytes, &defaultIndexSimilarity)
+		if err != nil {
+			return fmt.Errorf("fail to unmarshal: %v", err)
+		}
+		settings["index.similarity.default"] = defaultIndexSimilarity
+	}
+
 	// if date math is used, we need to pass the resolved name along to the read
 	// so we can pull the right result from the response
 	var resolvedName string

es/resource_elasticsearch_index_test.go

@@ -273,6 +273,19 @@ resource "elasticsearch_index" "test" {
 
   depends_on = [elasticsearch_index_template.test]
 }
+`
+
+	testAccElasticsearchIndexWithSimilarityConfig = `
+resource "elasticsearch_index" "test_similarity_config" {
+  name               = "terraform-test-update-similarity-module"
+  number_of_shards   = 1
+  number_of_replicas = 1
+  index_similarity_default = jsonencode({
+    "type" : "BM25",
+    "b" : 0.25,
+    "k1" : 1.2
+  })
+}
 `
 )
 
@@ -374,6 +387,22 @@ func TestAccElasticsearchIndex_dateMath(t *testing.T) {
 	})
 }
 
+func TestAccElasticsearchIndex_similarityConfig(t *testing.T) {
+	resource.Test(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t) },
+		Providers:    testAccProviders,
+		CheckDestroy: checkElasticsearchIndexDestroy,
+		Steps: []resource.TestStep{
+			{
+				Config: testAccElasticsearchIndexWithSimilarityConfig,
+				Check: resource.ComposeTestCheckFunc(
+					checkElasticsearchIndexExists("elasticsearch_index.test_similarity_config"),
+				),
+			},
+		},
+	})
+}
+
 func TestAccElasticsearchIndex_doctype(t *testing.T) {
 	provider := Provider()
 	diags := provider.Configure(context.Background(), &terraform.ResourceConfig{})