Suppress selection item aliasing for the actual count query.

We now no longer apply count selection filtering but rather skip select field aliasing when rendering a count query to drop the field alias within a count query.

Previously, we removed field aliasing by filtering the token stream which also removed the AS keyword from cast operators.

Closes: #3536
Original Pull Request: #3553

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

@@ -23,6 +23,7 @@ import java.util.List;
 
 import org.antlr.v4.runtime.ParserRuleContext;
 import org.springframework.data.domain.Sort;
+import org.springframework.data.jpa.repository.query.HqlParser.SelectionContext;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
@@ -331,6 +332,17 @@ class HqlQueryTransformer extends HqlQueryRenderer {
 		return tokens;
 	}
 
+	@Override
+	public List<JpaQueryParsingToken> visitSelection(SelectionContext ctx) {
+
+		if(!countQuery || isSubquery(ctx)) {
+			return super.visitSelection(ctx);
+		}
+
+		// do not append variables to skip AS field aliasing
+		return visit(ctx.selectExpression());
+	}
+
 	@Override
 	public List<JpaQueryParsingToken> visitSelectClause(HqlParser.SelectClauseContext ctx) {
 
@@ -339,6 +351,7 @@ class HqlQueryTransformer extends HqlQueryRenderer {
 		tokens.add(new JpaQueryParsingToken(ctx.SELECT()));
 
 		if (countQuery && !isSubquery(ctx)) {
+
 			tokens.add(TOKEN_COUNT_FUNC);
 
 			if (countProjection != null) {
@@ -358,14 +371,12 @@ class HqlQueryTransformer extends HqlQueryRenderer {
 
 				if (ctx.DISTINCT() != null) {
 
-					List<JpaQueryParsingToken> countSelection = QueryTransformers.filterCountSelection(selectionListTokens);
-
-					if (countSelection.stream().anyMatch(hqlToken -> hqlToken.getToken().contains("new"))) {
+					if (selectionListTokens.stream().anyMatch(hqlToken -> hqlToken.getToken().contains("new"))) {
 						// constructor
 						tokens.add(new JpaQueryParsingToken(() -> primaryFromAlias));
 					} else {
 						// keep all the select items to distinct against
-						tokens.addAll(countSelection);
+						tokens.addAll(selectionListTokens);
 					}
 				} else {
 					tokens.add(new JpaQueryParsingToken(() -> primaryFromAlias));

spring-data-jpa/src/test/java/org/springframework/data/jpa/repository/query/HqlQueryTransformerTests.java

@@ -85,6 +85,23 @@ class HqlQueryTransformerTests {
 		assertThat(results).isEqualTo("select count(e) FROM Employee e where e.name = :name");
 	}
 
+	@Test // GH-3536
+	void shouldCreateCountQueryForDistinctCount() {
+
+		// given
+		var original = """
+				select distinct cast(e.timestampField as date) as foo
+				from ExampleEntity e
+				order by cast(e.timestampField as date) desc
+				""";
+
+		// when
+		var results = createCountQueryFor(original);
+
+		// then
+		assertThat(results).isEqualTo("select count(distinct cast(e.timestampField as date)) from ExampleEntity e");
+	}
+
 	@Test
 	void applyCountToMoreComplexQuery() {
 
@@ -1037,9 +1054,9 @@ class HqlQueryTransformerTests {
 
 		assertCountQuery("select distinct 1 as x from Employee","select count(distinct 1) from Employee AS __");
 		assertCountQuery("SELECT DISTINCT abc AS x FROM T","SELECT count(DISTINCT abc) FROM T AS __");
-		assertCountQuery("select distinct a as x, b as y from Employee","select count(distinct a , b) from Employee AS __");
+		assertCountQuery("select distinct a as x, b as y from Employee","select count(distinct a, b) from Employee AS __");
 		assertCountQuery("select distinct sum(amount) as x from Employee GROUP BY n","select count(distinct sum(amount)) from Employee AS __ GROUP BY n");
-		assertCountQuery("select distinct a, b, sum(amount) as c, d from Employee GROUP BY n","select count(distinct a, b, sum(amount) , d) from Employee AS __ GROUP BY n");
+		assertCountQuery("select distinct a, b, sum(amount) as c, d from Employee GROUP BY n","select count(distinct a, b, sum(amount), d) from Employee AS __ GROUP BY n");
 		assertCountQuery("select distinct a, count(b) as c from Employee GROUP BY n","select count(distinct a, count(b)) from Employee AS __ GROUP BY n");
 	}