Polishing.

Inherit column name when using function builder.

See #1504

spring-data-cassandra/src/main/java/org/springframework/data/cassandra/core/query/ColumnName.java

@@ -75,6 +75,11 @@ public abstract class ColumnName {
 	 */
 	public abstract Optional<CqlIdentifier> getCqlIdentifier();
 
+	CqlIdentifier getRequiredCqlIdentifier() {
+		return getCqlIdentifier().or(() -> getColumnName().map(CqlIdentifier::fromCql))
+				.orElseGet(() -> CqlIdentifier.fromCql(toCql()));
+	}
+
 	/**
 	 * Represent the column name as CQL.
 	 *

spring-data-cassandra/src/main/java/org/springframework/data/cassandra/core/query/Columns.java

@@ -480,6 +480,10 @@ public class Columns implements Iterable<ColumnName> {
 			return new FunctionCall(expression, params, alias);
 		}
 
+		FunctionCall as(ColumnName alias) {
+			return new FunctionCall(expression, params, alias.getRequiredCqlIdentifier());
+		}
+
 		@Override
 		public String getExpression() {
 			return expression;
@@ -625,7 +629,7 @@ public class Columns implements Iterable<ColumnName> {
 
 		@Override
 		public Selector ttl() {
-			return FunctionCall.from("TTL", ColumnSelector.from(columnName));
+			return FunctionCall.from("TTL", ColumnSelector.from(columnName)).as(columnName);
 		}
 
 		@Override
@@ -657,7 +661,7 @@ public class Columns implements Iterable<ColumnName> {
 				@Override
 				public Selector using(SimilarityFunction similarityFunction) {
 					return FunctionCall.from("similarity_" + similarityFunction.name().toLowerCase(Locale.ROOT), columnName,
-							vector);
+							vector).as(columnName);
 				}
 			};
 		}