Remove prefer_v2_templates query string parameter (#56546)

This commit removes the `prefer_v2_templates` flag and setting. This was a brief setting that
allowed specifying whether V1 or V2 template should be used when an index is created. It has been
removed in favor of V2 templates always having priority.

Relates to #53101
Resolves #56528

This is not a breaking change because this flag was never in a released version.

client/rest-high-level/src/main/java/org/elasticsearch/client/IndicesRequestConverters.java

@@ -114,9 +114,6 @@ static Request createIndex(CreateIndexRequest createIndexRequest) throws IOExcep
         parameters.withTimeout(createIndexRequest.timeout());
         parameters.withMasterTimeout(createIndexRequest.masterNodeTimeout());
         parameters.withWaitForActiveShards(createIndexRequest.waitForActiveShards());
-        if (createIndexRequest.preferV2Templates() != null) {
-            parameters.putParam(IndexMetadata.PREFER_V2_TEMPLATES_FLAG, Boolean.toString(createIndexRequest.preferV2Templates()));
-        }
         request.addParameters(parameters.asMap());
         request.setEntity(RequestConverters.createEntity(createIndexRequest, RequestConverters.REQUEST_BODY_CONTENT_TYPE));
         return request;

client/rest-high-level/src/main/java/org/elasticsearch/client/RequestConverters.java

@@ -56,7 +56,6 @@
 import org.elasticsearch.client.security.RefreshPolicy;
 import org.elasticsearch.client.tasks.TaskId;
 import org.elasticsearch.cluster.health.ClusterHealthStatus;
-import org.elasticsearch.cluster.metadata.IndexMetadata;
 import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.Priority;
 import org.elasticsearch.common.Strings;
@@ -133,9 +132,6 @@ static Request bulk(BulkRequest bulkRequest) throws IOException {
         parameters.withRefreshPolicy(bulkRequest.getRefreshPolicy());
         parameters.withPipeline(bulkRequest.pipeline());
         parameters.withRouting(bulkRequest.routing());
-        if (bulkRequest.preferV2Templates() != null) {
-            parameters.putParam(IndexMetadata.PREFER_V2_TEMPLATES_FLAG, Boolean.toString(bulkRequest.preferV2Templates()));
-        }
         // Bulk API only supports newline delimited JSON or Smile. Before executing
         // the bulk, we need to check that all requests have the same content-type
         // and this content-type is supported by the Bulk API.
@@ -336,9 +332,6 @@ static Request index(IndexRequest indexRequest) {
         parameters.withPipeline(indexRequest.getPipeline());
         parameters.withRefreshPolicy(indexRequest.getRefreshPolicy());
         parameters.withWaitForActiveShards(indexRequest.waitForActiveShards());
-        if (indexRequest.preferV2Templates() != null) {
-            parameters.putParam(IndexMetadata.PREFER_V2_TEMPLATES_FLAG, Boolean.toString(indexRequest.preferV2Templates()));
-        }
 
         BytesRef source = indexRequest.source().toBytesRef();
         ContentType contentType = createContentType(indexRequest.getContentType());
@@ -365,9 +358,6 @@ static Request update(UpdateRequest updateRequest) throws IOException {
         parameters.withRetryOnConflict(updateRequest.retryOnConflict());
         parameters.withVersion(updateRequest.version());
         parameters.withVersionType(updateRequest.versionType());
-        if (updateRequest.preferV2Templates() != null) {
-            parameters.putParam(IndexMetadata.PREFER_V2_TEMPLATES_FLAG, Boolean.toString(updateRequest.preferV2Templates()));
-        }
 
         // The Java API allows update requests with different content types
         // set for the partial document and the upsert document. This client
@@ -579,10 +569,6 @@ private static Request prepareReindexRequest(ReindexRequest reindexRequest, bool
             params.putParam("scroll", reindexRequest.getScrollTime());
         }
 
-        if (reindexRequest.preferV2Templates() != null) {
-            params.putParam("prefer_v2_templates", reindexRequest.preferV2Templates().toString());
-        }
-
         request.addParameters(params.asMap());
         request.setEntity(createEntity(reindexRequest, REQUEST_BODY_CONTENT_TYPE));
         return request;

client/rest-high-level/src/main/java/org/elasticsearch/client/indices/CreateIndexRequest.java

@@ -25,7 +25,6 @@
 import org.elasticsearch.action.support.ActiveShardCount;
 import org.elasticsearch.client.TimedRequest;
 import org.elasticsearch.client.Validatable;
-import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.ParseField;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.bytes.BytesArray;
@@ -63,7 +62,6 @@ public class CreateIndexRequest extends TimedRequest implements Validatable, ToX
 
     private BytesReference mappings;
     private XContentType mappingsXContentType;
-    private Boolean preferV2Templates;
 
     private final Set<Alias> aliases = new HashSet<>();
 
@@ -267,16 +265,6 @@ public CreateIndexRequest aliases(Collection<Alias> aliases) {
         return this;
     }
 
-    public CreateIndexRequest preferV2Templates(Boolean preferV2Templates) {
-        this.preferV2Templates = preferV2Templates;
-        return this;
-    }
-
-    @Nullable
-    public Boolean preferV2Templates() {
-        return this.preferV2Templates;
-    }
-
     /**
      * Sets the settings and mappings as a single source.
      *

client/rest-high-level/src/test/java/org/elasticsearch/client/ReindexIT.java

@@ -23,20 +23,14 @@
 import org.elasticsearch.action.admin.cluster.node.tasks.list.ListTasksRequest;
 import org.elasticsearch.action.admin.cluster.node.tasks.list.ListTasksResponse;
 import org.elasticsearch.action.admin.cluster.node.tasks.list.TaskGroup;
-import org.elasticsearch.action.admin.indices.alias.get.GetAliasesRequest;
 import org.elasticsearch.action.bulk.BulkItemResponse;
 import org.elasticsearch.action.bulk.BulkRequest;
 import org.elasticsearch.action.get.GetRequest;
 import org.elasticsearch.action.index.IndexRequest;
 import org.elasticsearch.action.ingest.PutPipelineRequest;
 import org.elasticsearch.action.search.SearchRequest;
 import org.elasticsearch.action.support.WriteRequest;
-import org.elasticsearch.client.indices.PutIndexTemplateRequest;
-import org.elasticsearch.client.indices.PutIndexTemplateV2Request;
 import org.elasticsearch.client.tasks.TaskSubmissionResponse;
-import org.elasticsearch.cluster.metadata.AliasMetadata;
-import org.elasticsearch.cluster.metadata.IndexTemplateV2;
-import org.elasticsearch.cluster.metadata.Template;
 import org.elasticsearch.common.CheckedRunnable;
 import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.settings.Settings;
@@ -56,9 +50,6 @@
 
 import java.io.IOException;
 import java.util.Collections;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 import java.util.stream.Collectors;
@@ -122,44 +113,6 @@ public void testReindex() throws IOException {
         }
     }
 
-    public void testReindexPreferV2Templates() throws Exception {
-        //we don't care about warnings here
-        RequestOptions options = RequestOptions.DEFAULT.toBuilder().setWarningsHandler(warnings -> false).build();
-
-        IndexRequest indexRequest = new IndexRequest("sourcev2").source(Collections.singletonMap("foo", "bar"), XContentType.JSON);
-        indexRequest.setRefreshPolicy(WriteRequest.RefreshPolicy.IMMEDIATE);
-        RestHighLevelClient client = highLevelClient();
-        assertEquals(RestStatus.CREATED, client.index(indexRequest, options).status());
-
-        PutIndexTemplateRequest putIndexTemplateRequest = new PutIndexTemplateRequest("v1", Collections.singletonList("target*"));
-        assertTrue(client.indices().putTemplate(putIndexTemplateRequest, options).isAcknowledged());
-
-        AliasMetadata alias = AliasMetadata.builder("alias").build();
-        Template template = new Template(null, null, Map.of("alias", alias));
-        List<String> pattern = Collections.singletonList("target*");
-        IndexTemplateV2 indexTemplate = new IndexTemplateV2(pattern, template, Collections.emptyList(), 1L, 1L, new HashMap<>());
-        PutIndexTemplateV2Request putTemplateRequest = new PutIndexTemplateV2Request().name("v2").indexTemplate(indexTemplate);
-        assertTrue(client.indices().putIndexTemplate(putTemplateRequest, options).isAcknowledged());
-
-        ReindexRequest reindexRequest = new ReindexRequest()
-            .preferV2Templates(true)
-            .setSourceIndices("sourcev2")
-            .setDestIndex("target1")
-            .setRefresh(true);
-        assertEquals(1, client.reindex(reindexRequest, options).getStatus().getSuccessfullyProcessed());
-
-        GetAliasesResponse aliases = client.indices().getAlias(new GetAliasesRequest().indices("target1"), options);
-        assertEquals(RestStatus.OK, aliases.status());
-        assertEquals(Collections.singletonMap("target1", Collections.singleton(alias)), aliases.getAliases());
-
-        reindexRequest.setDestIndex("target2").preferV2Templates(false);
-        assertEquals(1, client.reindex(reindexRequest, options).getStatus().getSuccessfullyProcessed());
-
-        aliases = client.indices().getAlias(new GetAliasesRequest().indices("target2"), options);
-        assertEquals(RestStatus.OK, aliases.status());
-        assertEquals(Collections.singletonMap("target2", Collections.emptySet()), aliases.getAliases());
-    }
-
     public void testReindexTask() throws Exception {
         final String sourceIndex = "source123";
         final String destinationIndex = "dest2";

docs/reference/api-conventions.asciidoc

@@ -385,7 +385,6 @@ Returns:
     "settings": {
       "index.number_of_replicas": "1",
       "index.number_of_shards": "1",
-      "index.prefer_v2_templates": "true",
       "index.creation_date": "1474389951325",
       "index.uuid": "n6gzFZTgS664GUfx0Xrpjw",
       "index.version.created": ...,
@@ -422,8 +421,7 @@ Returns:
         "version": {
           "created": ...
         },
-        "provided_name" : "twitter",
-        "prefer_v2_templates": "true"
+        "provided_name" : "twitter"
       }
     }
   }

docs/reference/indices/index-templates.asciidoc

@@ -9,11 +9,9 @@ This documentation is about V2 (version 2) index templates. For V1 templates ple
 
 [NOTE]
 ====
-In {es} 7.8 the `prefer_v2_templates` querystring parameter was introduced to the index, update,
-bulk, and create index APIs to allow configuring whether to favor V2 or V1 index templates. In 7.x
-the default value for this parameter is `false` meaning that the <<indices-templates-v1,V1 index
-templates>> take precedence. In 8.x the default value for the parameter is `true` meaning that V2
-index templates take precedence (V1 templates may still match if no V2 template matches).
+In {es} 7.8 V2 templates were introduced. When a V2 index template matches a given index it always
+takes precedence over a V1 template. If no V2 index template matches, a V1 template may still match
+and be applied.
 ====
 
 An index template is a way to tell {es} how to configure an index when it is created. Templates are

docs/reference/indices/templates.asciidoc

@@ -9,11 +9,9 @@ replaced by V2 templates. For information about V2 templates, see <<indices-temp
 
 [NOTE]
 ====
-In {es} 7.8 the `prefer_v2_templates` querystring parameter was introduced to the index, update,
-bulk, and create index APIs to allow configuring whether to favor V2 or V1 index templates. In 7.x
-the default value for this parameter is `false` meaning that the V1 index templates take precedence.
-In 8.x the default value for the parameter is `true` meaning that <<indices-templates,V2 index
-templates>> take precedence (V1 templates may still match if no V2 template matches).
+In {es} 7.8 V2 templates were introduced. When a V2 index template matches a given index it always
+takes precedence over a V1 template. If no V2 index template matches, a V1 template may still match
+and be applied.
 ====
 
 Creates or updates an index template.

docs/reference/migration/migrate_8_0/settings.asciidoc

@@ -144,21 +144,3 @@ may be set to false.
 Discontinue use of the removed settings. Specifying these settings in
 `elasticsearch.yml` will result in an error on startup.
 ====
-
-.The `prefer_v2_templates` parameter now defaults to `true` for several document and index APIs.
-[%collapsible]
-====
-*Details* +
-In Elasticsearch 7.8.0 the `?prefer_v2_templates=true|false` parameter was introduced to allow
-specifying whether to favor V1 or V2 templates when a new index is created. In 8.0 this now defaults
-to `true`, meaning that V2 index templates will always take precedence if they match. V1 templates
-will continue to be applied if no V2 index template matches the newly created index pattern.
-
-The `?prefer_v2_templates` parameter is supported on the <<indices-create-index,Create Index>>,
-<<docs-index_,Index>>, <<docs-bulk,Bulk>>, <<docs-update,Update>>, and
-<<indices-rollover-index,Rollover>> APIs.
-
-*Impact* +
-Update your workflow and applications to assume a default value of `true` for
-the `prefer_v2_templates` query parameter.
-====

modules/reindex/src/main/java/org/elasticsearch/index/reindex/Reindexer.java

@@ -32,7 +32,6 @@
 import org.elasticsearch.action.ActionListener;
 import org.elasticsearch.action.bulk.BackoffPolicy;
 import org.elasticsearch.action.bulk.BulkItemResponse;
-import org.elasticsearch.action.bulk.BulkRequest;
 import org.elasticsearch.action.index.IndexRequest;
 import org.elasticsearch.client.Client;
 import org.elasticsearch.client.ParentTaskAssigningClient;
@@ -218,11 +217,6 @@ public BiFunction<RequestWrapper<?>, ScrollableHitSource.Hit, RequestWrapper<?>>
             return super.buildScriptApplier();
         }
 
-        @Override
-        protected BulkRequest buildBulk(Iterable<? extends ScrollableHitSource.Hit> docs) {
-            return super.buildBulk(docs).preferV2Templates(mainRequest.preferV2Templates());
-        }
-
         @Override
         protected RequestWrapper<IndexRequest> buildRequest(ScrollableHitSource.Hit doc) {
             IndexRequest index = new IndexRequest();

modules/reindex/src/main/java/org/elasticsearch/index/reindex/RestReindexAction.java

@@ -69,10 +69,6 @@ protected ReindexRequest buildRequest(RestRequest request) throws IOException {
             internal.setScroll(parseTimeValue(request.param("scroll"), "scroll"));
         }
 
-        if (request.hasParam("prefer_v2_templates")) {
-            internal.preferV2Templates(Boolean.parseBoolean(request.param("prefer_v2_templates")));
-        }
-
         return internal;
     }
 }

rest-api-spec/src/main/resources/rest-api-spec/api/bulk.json

@@ -87,10 +87,6 @@
       "pipeline":{
         "type":"string",
         "description":"The pipeline id to preprocess incoming documents with"
-      },
-      "prefer_v2_templates": {
-        "type": "boolean",
-        "description": "favor V2 templates instead of V1 templates during automatic index creation"
       }
     },
     "body":{

rest-api-spec/src/main/resources/rest-api-spec/api/create.json

@@ -90,10 +90,6 @@
       "pipeline":{
         "type":"string",
         "description":"The pipeline id to preprocess incoming documents with"
-      },
-      "prefer_v2_templates": {
-        "type": "boolean",
-        "description": "favor V2 templates instead of V1 templates during automatic index creation"
       }
     },
     "body":{

rest-api-spec/src/main/resources/rest-api-spec/api/index.json

@@ -92,10 +92,6 @@
       "pipeline":{
         "type":"string",
         "description":"The pipeline id to preprocess incoming documents with"
-      },
-      "prefer_v2_templates": {
-        "type": "boolean",
-        "description": "favor V2 templates instead of V1 templates during automatic index creation"
       }
     },
     "body":{

rest-api-spec/src/main/resources/rest-api-spec/api/indices.create.json

@@ -33,10 +33,6 @@
       "master_timeout":{
         "type":"time",
         "description":"Specify timeout for connection to master"
-      },
-      "prefer_v2_templates": {
-        "type": "boolean",
-        "description": "favor V2 templates instead of V1 templates during index creation"
       }
     },
     "body":{

rest-api-spec/src/main/resources/rest-api-spec/api/indices.rollover.json

@@ -53,10 +53,6 @@
       "wait_for_active_shards":{
         "type":"string",
         "description":"Set the number of active shards to wait for on the newly created rollover index before the operation returns."
-      },
-      "prefer_v2_templates": {
-        "type": "boolean",
-        "description": "favor V2 templates instead of V1 templates during automatic index creation"
       }
     },
     "body":{

rest-api-spec/src/main/resources/rest-api-spec/api/reindex.json

@@ -52,10 +52,6 @@
       "max_docs":{
         "type":"number",
         "description":"Maximum number of documents to process (default: all documents)"
-      },
-      "prefer_v2_templates": {
-        "type": "boolean",
-        "description": "favor V2 templates instead of V1 templates during index creation"
       }
     },
     "body":{

rest-api-spec/src/main/resources/rest-api-spec/api/update.json

@@ -99,10 +99,6 @@
       "if_primary_term":{
         "type":"number",
         "description":"only perform the update operation if the last operation that has changed the document has the specified primary term"
-      },
-      "prefer_v2_templates": {
-        "type": "boolean",
-        "description": "favor V2 templates instead of V1 templates during automatic index creation"
       }
     },
     "body":{