Make SearchType in query nullable, set to null in NativeQuery with knnQuery.

Original Pull Request #2570
Closes #2569

Author: sothawo

src/main/java/org/springframework/data/elasticsearch/client/elc/RequestConverter.java

@@ -22,6 +22,7 @@
 import co.elastic.clients.elasticsearch._types.FieldValue;
 import co.elastic.clients.elasticsearch._types.InlineScript;
 import co.elastic.clients.elasticsearch._types.OpType;
+import co.elastic.clients.elasticsearch._types.SearchType;
 import co.elastic.clients.elasticsearch._types.SortOptions;
 import co.elastic.clients.elasticsearch._types.SortOrder;
 import co.elastic.clients.elasticsearch._types.VersionType;
@@ -1153,9 +1154,12 @@ public MsearchRequest searchMsearchRequest(
 				var query = param.query();
 				mrb.searches(sb -> sb //
 						.header(h -> {
+							var searchType = (query instanceof NativeQuery nativeQuery && nativeQuery.getKnnQuery() != null) ? null
+									: searchType(query.getSearchType());
+
 							h //
 									.index(Arrays.asList(param.index().getIndexNames())) //
-									.searchType(searchType(query.getSearchType())) //
+									.searchType(searchType) //
 									.requestCache(query.getRequestCache()) //
 							;
 
@@ -1256,8 +1260,8 @@ public MsearchRequest searchMsearchRequest(
 							query.getScriptedFields().forEach(scriptedField -> bb.scriptFields(scriptedField.getFieldName(),
 									sf -> sf.script(getScript(scriptedField.getScriptData()))));
 
-							if (query instanceof NativeQuery) {
-								prepareNativeSearch((NativeQuery) query, bb);
+							if (query instanceof NativeQuery nativeQuery) {
+								prepareNativeSearch(nativeQuery, bb);
 							}
 							return bb;
 						} //
@@ -1279,12 +1283,15 @@ private <T> void prepareSearchRequest(Query query, @Nullable String routing, @Nu
 
 		ElasticsearchPersistentEntity<?> persistentEntity = getPersistentEntity(clazz);
 
+		var searchType = (query instanceof NativeQuery nativeQuery && nativeQuery.getKnnQuery() != null) ? null
+				: searchType(query.getSearchType());
+
 		builder //
 				.version(true) //
 				.trackScores(query.getTrackScores()) //
 				.allowNoIndices(query.getAllowNoIndices()) //
 				.source(getSourceConfig(query)) //
-				.searchType(searchType(query.getSearchType())) //
+				.searchType(searchType) //
 				.timeout(timeStringMs(query.getTimeout())) //
 				.requestCache(query.getRequestCache()) //
 		;
@@ -1361,8 +1368,8 @@ private <T> void prepareSearchRequest(Query query, @Nullable String routing, @Nu
 		query.getScriptedFields().forEach(scriptedField -> builder.scriptFields(scriptedField.getFieldName(),
 				sf -> sf.script(getScript(scriptedField.getScriptData()))));
 
-		if (query instanceof NativeQuery) {
-			prepareNativeSearch((NativeQuery) query, builder);
+		if (query instanceof NativeQuery nativeQuery) {
+			prepareNativeSearch(nativeQuery, builder);
 		}
 
 		if (query.getTrackTotalHits() != null) {

src/main/java/org/springframework/data/elasticsearch/core/query/BaseQuery.java

@@ -58,7 +58,7 @@ public class BaseQuery implements Query {
 	protected float minScore;
 	@Nullable protected Collection<String> ids;
 	@Nullable protected String route;
-	protected SearchType searchType = SearchType.QUERY_THEN_FETCH;
+	@Nullable protected SearchType searchType = SearchType.QUERY_THEN_FETCH;
 	@Nullable protected IndicesOptions indicesOptions;
 	protected boolean trackScores;
 	@Nullable protected String preference;
@@ -278,10 +278,11 @@ public void setRoute(String route) {
 		this.route = route;
 	}
 
-	public void setSearchType(SearchType searchType) {
+	public void setSearchType(@Nullable SearchType searchType) {
 		this.searchType = searchType;
 	}
 
+	@Nullable
 	@Override
 	public SearchType getSearchType() {
 		return searchType;

src/main/java/org/springframework/data/elasticsearch/core/query/BaseQueryBuilder.java

@@ -46,7 +46,7 @@ public abstract class BaseQueryBuilder<Q extends BaseQuery, SELF extends BaseQue
 	private float minScore;
 	private final Collection<String> ids = new ArrayList<>();
 	@Nullable private String route;
-	private Query.SearchType searchType = Query.SearchType.QUERY_THEN_FETCH;
+	@Nullable private Query.SearchType searchType = Query.SearchType.QUERY_THEN_FETCH;
 	@Nullable private IndicesOptions indicesOptions;
 	private boolean trackScores;
 	@Nullable private String preference;
@@ -140,6 +140,7 @@ public List<IndexBoost> getIndicesBoost() {
 		return indicesBoost;
 	}
 
+	@Nullable
 	public Query.SearchType getSearchType() {
 		return searchType;
 	}
@@ -250,23 +251,23 @@ public SELF withMaxResults(Integer maxResults) {
 		return self();
 	}
 
-		/**
-		 * Set Ids for a multi-get request run with this query. Not used in any other searches.
-		 *
-		 * @param ids list of id values
-		 */
+	/**
+	 * Set Ids for a multi-get request run with this query. Not used in any other searches.
+	 *
+	 * @param ids list of id values
+	 */
 	public SELF withIds(String... ids) {
 
 		this.ids.clear();
 		this.ids.addAll(Arrays.asList(ids));
 		return self();
 	}
 
-		/**
-		 * Set Ids for a multi-get request run with this query. Not used in any other searches.
-		 *
-		 * @param ids list of id values
-		 */
+	/**
+	 * Set Ids for a multi-get request run with this query. Not used in any other searches.
+	 *
+	 * @param ids list of id values
+	 */
 	public SELF withIds(Collection<String> ids) {
 
 		Assert.notNull(ids, "ids must not be null");
@@ -342,7 +343,7 @@ public SELF withIndicesBoost(IndexBoost... indicesBoost) {
 		return self();
 	}
 
-	public SELF withSearchType(Query.SearchType searchType) {
+	public SELF withSearchType(@Nullable Query.SearchType searchType) {
 		this.searchType = searchType;
 		return self();
 	}
@@ -382,12 +383,12 @@ public SELF withRequestCache(@Nullable Boolean requestCache) {
 		return self();
 	}
 
-		/**
-		 * Set Ids with routing values for a multi-get request run with this query. Not used in any other searches.
-		 *
-		 * @param idsWithRouting list of id values, must not be {@literal null}
-		 * @since 4.3
-		 */
+	/**
+	 * Set Ids with routing values for a multi-get request run with this query. Not used in any other searches.
+	 *
+	 * @param idsWithRouting list of id values, must not be {@literal null}
+	 * @since 4.3
+	 */
 	public SELF withIdsWithRouting(List<Query.IdWithRouting> idsWithRouting) {
 
 		Assert.notNull(idsWithRouting, "idsWithRouting must not be null");

src/main/java/org/springframework/data/elasticsearch/core/query/Query.java

@@ -221,6 +221,7 @@ static Query multiGetQuery(Collection<String> ids) {
 	 *
 	 * @return
 	 */
+	@Nullable
 	SearchType getSearchType();
 
 	/**