Optimize QueryTokenStream handling.

This commit moves EQL and HQL parsers to QueryTokenStream and optimizes composite renderers as well as JSQLParser usage.
We also avoid Single-thread construction on each parse run to avoid thread creation overhead.

See: #3309

Author: mp911de

spring-data-jpa-performance/src/test/java/org/springframework/data/jpa/repository/Profiler.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright 2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.jpa.repository.query;
+
+import java.util.Collections;
+import java.util.Iterator;
+
+/**
+ * Empty QueryTokenStream.
+ *
+ * @author Mark Paluch
+ * @since 3.4
+ */
+class EmptyQueryTokenStream implements QueryTokenStream {
+
+	static final EmptyQueryTokenStream INSTANCE = new EmptyQueryTokenStream();
+
+	private EmptyQueryTokenStream() {}
+
+	@Override
+	public QueryToken getFirst() {
+		return null;
+	}
+
+	@Override
+	public QueryToken getLast() {
+		return null;
+	}
+
+	@Override
+	public boolean isExpression() {
+		return false;
+	}
+
+	@Override
+	public int size() {
+		return 0;
+	}
+
+	@Override
+	public boolean isEmpty() {
+		return true;
+	}
+
+	@Override
+	public Iterator<QueryToken> iterator() {
+		return Collections.emptyIterator();
+	}
+}

spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/query/EmptyQueryTokenStream.java

@@ -15,7 +15,7 @@
  */
 package org.springframework.data.jpa.repository.query;
 
-import static org.springframework.data.jpa.repository.query.JpaQueryParsingToken.*;
+import static org.springframework.data.jpa.repository.query.QueryTokens.*;
 
 import org.springframework.data.jpa.repository.query.QueryRenderer.QueryRendererBuilder;
 import org.springframework.data.jpa.repository.query.QueryTransformers.CountSelectionTokenStream;
@@ -62,42 +62,42 @@ public QueryRendererBuilder visitSelect_statement(EqlParser.Select_statementCont
 	}
 
 	@Override
-	public QueryRendererBuilder visitSelect_clause(EqlParser.Select_clauseContext ctx) {
+	public QueryTokenStream visitSelect_clause(EqlParser.Select_clauseContext ctx) {
 
 		QueryRendererBuilder builder = QueryRenderer.builder();
 
-		builder.append(JpaQueryParsingToken.expression(ctx.SELECT()));
+		builder.append(QueryTokens.expression(ctx.SELECT()));
 		builder.append(TOKEN_COUNT_FUNC);
 
 		if (countProjection != null) {
-			builder.append(JpaQueryParsingToken.token(countProjection));
+			builder.append(QueryTokens.token(countProjection));
 		}
 
 		QueryRendererBuilder nested = QueryRenderer.builder();
 
 		if (ctx.DISTINCT() != null) {
-			nested.append(JpaQueryParsingToken.expression(ctx.DISTINCT()));
+			nested.append(QueryTokens.expression(ctx.DISTINCT()));
 		}
 
 		if (countProjection == null) {
 
 			if (ctx.DISTINCT() != null) {
 
-				QueryRendererBuilder selectionListbuilder = QueryRendererBuilder.concat(ctx.select_item(), this::visit,
+				QueryTokenStream selectionListbuilder = QueryTokenStream.concat(ctx.select_item(), this::visit,
 						TOKEN_COMMA);
 
 				CountSelectionTokenStream countSelection = QueryTransformers
 						.filterCountSelection(selectionListbuilder);
 
 				if (countSelection.requiresPrimaryAlias()) {
 					// constructor
-					nested.append(new JpaQueryParsingToken(primaryFromAlias));
+					nested.append(QueryTokens.token(primaryFromAlias));
 				} else {
 					// keep all the select items to distinct against
 					nested.append(countSelection);
 				}
 			} else {
-				nested.append(new JpaQueryParsingToken(primaryFromAlias));
+				nested.append(QueryTokens.token(primaryFromAlias));
 			}
 		}
 

spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/query/EqlCountQueryTransformer.java

@@ -15,7 +15,7 @@
  */
 package org.springframework.data.jpa.repository.query;
 
-import static org.springframework.data.jpa.repository.query.JpaQueryParsingToken.*;
+import static org.springframework.data.jpa.repository.query.QueryTokens.*;
 
 import java.util.ArrayList;
 import java.util.Collections;
@@ -34,7 +34,7 @@ class EqlQueryIntrospector extends EqlBaseVisitor<Void> implements ParsedQueryIn
 	private final EqlQueryRenderer renderer = new EqlQueryRenderer();
 
 	private @Nullable String primaryFromAlias = null;
-	private @Nullable List<JpaQueryParsingToken> projection;
+	private @Nullable List<QueryToken> projection;
 	private boolean projectionProcessed;
 	private boolean hasConstructorExpression = false;
 
@@ -44,7 +44,7 @@ public String getAlias() {
 	}
 
 	@Override
-	public List<JpaQueryParsingToken> getProjection() {
+	public List<QueryToken> getProjection() {
 		return projection == null ? Collections.emptyList() : projection;
 	}
 
@@ -57,15 +57,15 @@ public boolean hasConstructorExpression() {
 	public Void visitSelect_clause(EqlParser.Select_clauseContext ctx) {
 
 		List<EqlParser.Select_itemContext> selections = ctx.select_item();
-		List<JpaQueryParsingToken> selectItemTokens = new ArrayList<>(selections.size() * 2);
+		List<QueryToken> selectItemTokens = new ArrayList<>(selections.size() * 2);
 
 		for (EqlParser.Select_itemContext selection : selections) {
 
 			if (!selectItemTokens.isEmpty()) {
 				selectItemTokens.add(TOKEN_COMMA);
 			}
 
-			selectItemTokens.add(JpaQueryParsingToken.token(renderer.visitSelect_item(selection).build().render()));
+			selectItemTokens.add(QueryTokens.token(QueryRenderer.from(renderer.visitSelect_item(selection)).render()));
 		}
 
 		if (!projectionProcessed) {