[CALCITE-7474] LAST in MATCH_RECOGNIZE might return wrong result

core/src/main/java/org/apache/calcite/adapter/enumerable/MatchUtils.java

@@ -27,7 +27,7 @@ private MatchUtils() {
   }
 
   /**
-   * Returns the row with the highest index whose corresponding symbol matches, null otherwise.
+   * Returns the highest index whose corresponding symbol matches, -1 otherwise.
    *
    * @param symbol Target Symbol
    * @param rows List of passed rows
@@ -44,6 +44,23 @@ public static <E> int lastWithSymbol(String symbol, List<E> rows, List<String> s
     return -1;
   }
 
+  /**
+   * Returns the highest index whose corresponding symbol matches, startIndex otherwise.
+   *
+   * @param symbol Target Symbol
+   * @param symbols Corresponding symbols to rows
+   * @return index or startIndex
+   */
+  public static int lastWithSymbolOrLast(String symbol, List<String> symbols,
+      int startIndex) {
+    for (int i = startIndex; i >= 0; i--) {
+      if (symbol.equals(symbols.get(i))) {
+        return i;
+      }
+    }
+    return startIndex;
+  }
+
   public static void print(int s) {
     System.out.println(s);
   }

core/src/main/java/org/apache/calcite/adapter/enumerable/RexImpTable.java

@@ -22,7 +22,6 @@
 import org.apache.calcite.avatica.util.DateTimeUtils;
 import org.apache.calcite.avatica.util.TimeUnit;
 import org.apache.calcite.avatica.util.TimeUnitRange;
-import org.apache.calcite.linq4j.tree.BinaryExpression;
 import org.apache.calcite.linq4j.tree.BlockBuilder;
 import org.apache.calcite.linq4j.tree.BlockStatement;
 import org.apache.calcite.linq4j.tree.ConstantExpression;
@@ -4173,43 +4172,27 @@ private static class LastImplementor implements MatchImplementor {
 
       final String alpha = ((RexPatternFieldRef) call.getOperands().get(0)).getAlpha();
 
-      // TODO: verify if the variable is needed
-      @SuppressWarnings("unused")
-      final BinaryExpression lastIndex =
-          Expressions.subtract(
-              Expressions.call(rows, BuiltInMethod.COLLECTION_SIZE.method),
-              Expressions.constant(1));
-
       // Just take the last one, if exists
       if ("*".equals(alpha)) {
         setInputGetterIndex(translator, i);
-        // Important, unbox the node / expression to avoid NullAs.NOT_POSSIBLE
-        final RexPatternFieldRef ref = (RexPatternFieldRef) node;
-        final RexPatternFieldRef newRef =
-            new RexPatternFieldRef(ref.getAlpha(),
-                ref.getIndex(),
-                translator.typeFactory.createTypeWithNullability(ref.getType(),
-                    true));
-        final Expression expression = translator.translate(newRef, NullAs.NULL);
-        setInputGetterIndex(translator, null);
-        return expression;
       } else {
         // Alpha != "*" so we have to search for a specific one to find and use that, if found
+        // otherwise pick the last one
         setInputGetterIndex(translator,
-            Expressions.call(BuiltInMethod.MATCH_UTILS_LAST_WITH_SYMBOL.method,
-                Expressions.constant(alpha), rows, symbols, i));
-
-        // Important, unbox the node / expression to avoid NullAs.NOT_POSSIBLE
-        final RexPatternFieldRef ref = (RexPatternFieldRef) node;
-        final RexPatternFieldRef newRef =
-            new RexPatternFieldRef(ref.getAlpha(),
-                ref.getIndex(),
-                translator.typeFactory.createTypeWithNullability(ref.getType(),
-                    true));
-        final Expression expression = translator.translate(newRef, NullAs.NULL);
-        setInputGetterIndex(translator, null);
-        return expression;
+            Expressions.call(BuiltInMethod.MATCH_UTILS_LAST_WITH_SYMBOL_OR_LAST.method,
+                Expressions.constant(alpha), symbols, i));
       }
+
+      // Important, unbox the node / expression to avoid NullAs.NOT_POSSIBLE
+      final RexPatternFieldRef ref = (RexPatternFieldRef) node;
+      final RexPatternFieldRef newRef =
+          new RexPatternFieldRef(ref.getAlpha(),
+              ref.getIndex(),
+              translator.typeFactory.createTypeWithNullability(ref.getType(),
+                  true));
+      final Expression expression = translator.translate(newRef, NullAs.NULL);
+      setInputGetterIndex(translator, null);
+      return expression;
     }
 
     private static void setInputGetterIndex(RexToLixTranslator translator, @Nullable Expression o) {

core/src/main/java/org/apache/calcite/util/BuiltInMethod.java

@@ -245,6 +245,8 @@ public enum BuiltInMethod {
   MATCHER_BUILDER_BUILD(Matcher.Builder.class, "build"),
   MATCH_UTILS_LAST_WITH_SYMBOL(MatchUtils.class, "lastWithSymbol", String.class,
       List.class, List.class, int.class),
+  MATCH_UTILS_LAST_WITH_SYMBOL_OR_LAST(MatchUtils.class, "lastWithSymbolOrLast", String.class,
+      List.class, int.class),
   EMITTER_EMIT(Enumerables.Emitter.class, "emit", List.class, List.class,
       List.class, int.class, Consumer.class),
   MERGE_JOIN(EnumerableDefaults.class, "mergeJoin", Enumerable.class,

core/src/test/resources/sql/match.iq

@@ -140,6 +140,22 @@ C    EMPID
 
 !ok
 
+# Test Simple LAST with expanded column name
+# Test case for CALCITE-7474
+select *
+from "hr"."emps" match_recognize (
+    order by "empid" desc
+    measures "commission" as c,
+    LAST("hr"."emps"."empid") as empid
+    pattern (s up)
+    define up as up."commission" < prev(up."commission"));
+C    EMPID
+---- -----
+1000   100
+ 500   200
+
+!ok
+
 # Test LAST with Classifier
 select *
 from "hr"."emps" match_recognize (