Differentiate between JPQL and native queries in count query derivation.

We now consider whether a query is a native one when deriving a count query for pagination. Previously, the generated queries used JPQL syntax that doesn't comply with native SQL syntax rules.

Closes #2773
Original pull request #2777

Author: mp911de

src/main/java/org/springframework/data/jpa/repository/query/DefaultQueryEnhancer.java

@@ -46,7 +46,7 @@ public String detectAlias() {
 
 	@Override
 	public String createCountQueryFor(@Nullable String countProjection) {
-		return QueryUtils.createCountQueryFor(this.query.getQueryString(), countProjection);
+		return QueryUtils.createCountQueryFor(this.query.getQueryString(), countProjection, this.query.isNativeQuery());
 	}
 
 	@Override

src/main/java/org/springframework/data/jpa/repository/query/JSqlParserQueryEnhancer.java

@@ -15,9 +15,8 @@
  */
 package org.springframework.data.jpa.repository.query;
 
-import static org.springframework.data.jpa.repository.query.JSqlParserUtils.getJSqlCount;
-import static org.springframework.data.jpa.repository.query.JSqlParserUtils.getJSqlLower;
-import static org.springframework.data.jpa.repository.query.QueryUtils.checkSortExpression;
+import static org.springframework.data.jpa.repository.query.JSqlParserUtils.*;
+import static org.springframework.data.jpa.repository.query.QueryUtils.*;
 
 import net.sf.jsqlparser.JSQLParserException;
 import net.sf.jsqlparser.expression.Alias;
@@ -414,7 +413,7 @@ public String createCountQueryFor(@Nullable String countProjection) {
 			return selectBody.toString();
 		}
 
-		String countProp = tableAlias == null ? "*" : tableAlias;
+		String countProp = query.isNativeQuery() ? (distinct ? "*" : "1") : tableAlias == null ? "*" : tableAlias;
 
 		Function jSqlCount = getJSqlCount(Collections.singletonList(countProp), distinct);
 		selectBody.setSelectItems(Collections.singletonList(new SelectExpressionItem(jSqlCount)));

src/main/java/org/springframework/data/jpa/repository/query/QueryUtils.java

@@ -570,6 +570,19 @@ public static String createCountQueryFor(String originalQuery) {
 	 */
 	@Deprecated
 	public static String createCountQueryFor(String originalQuery, @Nullable String countProjection) {
+		return createCountQueryFor(originalQuery, countProjection, false);
+	}
+
+	/**
+	 * Creates a count projected query from the given original query.
+	 *
+	 * @param originalQuery must not be {@literal null}.
+	 * @param countProjection may be {@literal null}.
+	 * @param nativeQuery whether the underlying query is a native query.
+	 * @return a query String to be used a count query for pagination. Guaranteed to be not {@literal null}.
+	 * @since 2.7.8
+	 */
+	static String createCountQueryFor(String originalQuery, @Nullable String countProjection, boolean nativeQuery) {
 
 		Assert.hasText(originalQuery, "OriginalQuery must not be null or empty!");
 
@@ -591,9 +604,14 @@ public static String createCountQueryFor(String originalQuery, @Nullable String
 
 			String replacement = useVariable ? SIMPLE_COUNT_VALUE : complexCountValue;
 
-			String alias = QueryUtils.detectAlias(originalQuery);
-			if ("*".equals(variable) && alias != null) {
-				replacement = alias;
+			if (nativeQuery && (variable.contains(",") || "*".equals(variable))) {
+				replacement = "1";
+			} else {
+
+				String alias = QueryUtils.detectAlias(originalQuery);
+				if (("*".equals(variable) && alias != null)) {
+					replacement = alias;
+				}
 			}
 
 			countQuery = matcher.replaceFirst(String.format(COUNT_REPLACEMENT_TEMPLATE, replacement));

src/test/java/org/springframework/data/jpa/repository/query/QueryEnhancerUnitTests.java

@@ -228,7 +228,12 @@ void createsCountQueryForNestedReferenceCorrectly() {
 
 	@Test // DATAJPA-420
 	void createsCountQueryForScalarSelects() {
-		assertCountQuery("select p.lastname,p.firstname from Person p", "select count(p) from Person p", true);
+		assertCountQuery("select p.lastname,p.firstname from Person p", "select count(p) from Person p", false);
+	}
+
+	@Test // DATAJPA-420
+	void createsCountQueryForNativeScalarSelects() {
+		assertCountQuery("select p.lastname,p.firstname from Person p", "select count(1) from Person p", true);
 	}
 
 	@Test // DATAJPA-456
@@ -487,7 +492,7 @@ void createCountQuerySupportsWhitespaceCharacters() {
 				"  order by user.name\n ", true);
 
 		assertThat(getEnhancer(query).createCountQueryFor())
-				.isEqualToIgnoringCase("select count(user) from User user where user.age = 18");
+				.isEqualToIgnoringCase("select count(1) from User user where user.age = 18");
 	}
 
 	@Test
@@ -500,7 +505,7 @@ void createCountQuerySupportsLineBreaksInSelectClause() {
 				"  order\nby\nuser.name\n ", true);
 
 		assertThat(getEnhancer(query).createCountQueryFor())
-				.isEqualToIgnoringCase("select count(user) from User user where user.age = 18");
+				.isEqualToIgnoringCase("select count(1) from User user where user.age = 18");
 	}
 
 	@Test // DATAJPA-1061
@@ -721,17 +726,17 @@ void countQueryUsesCorrectVariable() {
 
 		QueryEnhancer queryEnhancer = getEnhancer(nativeQuery);
 		String countQueryFor = queryEnhancer.createCountQueryFor();
-		assertThat(countQueryFor).isEqualTo("SELECT count(*) FROM User WHERE created_at > $1");
+		assertThat(countQueryFor).isEqualTo("SELECT count(1) FROM User WHERE created_at > $1");
 
 		nativeQuery = new StringQuery("SELECT * FROM (select * from test) ", true);
 		queryEnhancer = getEnhancer(nativeQuery);
 		countQueryFor = queryEnhancer.createCountQueryFor();
-		assertThat(countQueryFor).isEqualTo("SELECT count(*) FROM (SELECT * FROM test)");
+		assertThat(countQueryFor).isEqualTo("SELECT count(1) FROM (SELECT * FROM test)");
 
 		nativeQuery = new StringQuery("SELECT * FROM (select * from test) as test", true);
 		queryEnhancer = getEnhancer(nativeQuery);
 		countQueryFor = queryEnhancer.createCountQueryFor();
-		assertThat(countQueryFor).isEqualTo("SELECT count(test) FROM (SELECT * FROM test) AS test");
+		assertThat(countQueryFor).isEqualTo("SELECT count(1) FROM (SELECT * FROM test) AS test");
 	}
 
 	@Test // GH-2555
@@ -861,7 +866,7 @@ void withStatementsWorksWithJSQLParser() {
 
 		assertThat(queryEnhancer.createCountQueryFor()).isEqualToIgnoringCase(
 				"with sample_data (day, value) AS (VALUES ((0, 13), (1, 12), (2, 15), (3, 4), (4, 8), (5, 16)))\n"
-						+ "SELECT count(a) FROM sample_data AS a");
+						+ "SELECT count(1) FROM sample_data AS a");
 		assertThat(queryEnhancer.applySorting(Sort.by("day").descending())).endsWith("ORDER BY a.day DESC");
 		assertThat(queryEnhancer.getJoinAliases()).isEmpty();
 		assertThat(queryEnhancer.detectAlias()).isEqualToIgnoringCase("a");
@@ -884,7 +889,7 @@ void multipleWithStatementsWorksWithJSQLParser() {
 
 		assertThat(queryEnhancer.createCountQueryFor()).isEqualToIgnoringCase(
 				"with sample_data (day, value) AS (VALUES ((0, 13), (1, 12), (2, 15), (3, 4), (4, 8), (5, 16))),test2 AS (VALUES (1, 2, 3))\n"
-						+ "SELECT count(a) FROM sample_data AS a");
+						+ "SELECT count(1) FROM sample_data AS a");
 		assertThat(queryEnhancer.applySorting(Sort.by("day").descending())).endsWith("ORDER BY a.day DESC");
 		assertThat(queryEnhancer.getJoinAliases()).isEmpty();
 		assertThat(queryEnhancer.detectAlias()).isEqualToIgnoringCase("a");
@@ -989,4 +994,5 @@ private static void endsIgnoringCase(String original, String endWithIgnoreCase)
 	private static QueryEnhancer getEnhancer(DeclaredQuery query) {
 		return QueryEnhancerFactory.forQuery(query);
 	}
+
 }