[CALCITE-7273] CoreRules.JOIN_REDUCE_EXPRESSIONS throws when applied to an ASOF JOIN

Signed-off-by: Mihai Budiu <mbudiu@feldera.com>

Author: mihaibudiu

core/src/main/java/org/apache/calcite/rel/rules/ReduceExpressionsRule.java

@@ -30,6 +30,7 @@
 import org.apache.calcite.rel.core.Join;
 import org.apache.calcite.rel.core.Project;
 import org.apache.calcite.rel.core.Window;
+import org.apache.calcite.rel.logical.LogicalAsofJoin;
 import org.apache.calcite.rel.logical.LogicalCalc;
 import org.apache.calcite.rel.logical.LogicalFilter;
 import org.apache.calcite.rel.logical.LogicalProject;
@@ -373,6 +374,12 @@ public JoinReduceExpressionsRule(Class<? extends Join> joinClass,
 
     @Override public void onMatch(RelOptRuleCall call) {
       final Join join = call.rel(0);
+      if (join instanceof LogicalAsofJoin) {
+        // Currently ASOF JOINs are restricted by the validator to use very specific
+        // conditions, so there isn't much to simplify about them.
+        // Moreover, calling join.copy() below for an ASOF JOIN will throw.
+        return;
+      }
       final List<RexNode> expList = Lists.newArrayList(join.getCondition());
       final int fieldCount = join.getLeft().getRowType().getFieldCount();
       final RelMetadataQuery mq = call.getMetadataQuery();

core/src/test/java/org/apache/calcite/test/RelOptRulesTest.java

@@ -3391,6 +3391,19 @@ private void checkPushJoinThroughUnionOnRightDoesNotMatchSemiOrAntiJoin(JoinRelT
         .checkUnchanged();
   }
 
+  /** Test case for <a href="https://issues.apache.org/jira/browse/CALCITE-7273">[CALCITE-7273]
+   *  CoreRules.JOIN_REDUCE_EXPRESSIONS throws when applied to an ASOF JOIN</a>. */
+  @Test void testAsofOptJoin() {
+    // Had to use ROW values to cause the optimization rule to match
+    final String sql = "SELECT *\n"
+        + "FROM (VALUES (NULL, ROW(0, 1)), (1, ROW(0, 2))) AS t1(k, t)\n"
+        + "ASOF JOIN (VALUES (2, ROW(0, 3))) AS t2(k, t)\n"
+        + "MATCH_CONDITION t2.t < t1.t\n"
+        + "ON t1.k = t2.k\n";
+    sql(sql).withRule(CoreRules.JOIN_REDUCE_EXPRESSIONS)
+        .checkUnchanged();
+  }
+
   /** Tests to see if the final branch of union is missed. */
   @Test void testUnionMergeRule() {
     final String sql = "select * from (\n"

core/src/test/resources/org/apache/calcite/test/RelOptRulesTest.xml

@@ -1586,6 +1586,30 @@ LogicalProject(K=[$0], T=[$1], K0=[$2], T0=[$3])
   LogicalAsofJoin(condition=[=($0, $2)], joinType=[asof], matchCondition=[<($3, $1)])
     LogicalValues(tuples=[[{ null, 0 }, { 1, null }, { 1, 0 }, { 1, 1 }, { 1, 2 }, { 1, 3 }, { 1, 4 }, { 2, 3 }, { 3, 4 }]])
     LogicalValues(tuples=[[{ 1, null }, { 1, 2 }, { 1, 3 }, { 2, 10 }, { 2, 0 }]])
+]]>
+    </Resource>
+  </TestCase>
+  <TestCase name="testAsofOptJoin">
+    <Resource name="sql">
+      <![CDATA[SELECT *
+FROM (VALUES (NULL, ROW(0, 1)), (1, ROW(0, 2))) AS t1(k, t)
+ASOF JOIN (VALUES (2, ROW(0, 3))) AS t2(k, t)
+MATCH_CONDITION t2.t < t1.t
+ON t1.k = t2.k
+]]>
+    </Resource>
+    <Resource name="planBefore">
+      <![CDATA[
+LogicalProject(K=[$0], T=[$1], K0=[$2], T0=[$3])
+  LogicalAsofJoin(condition=[=($0, $2)], joinType=[asof], matchCondition=[<($3, $1)])
+    LogicalProject(K=[$0], T=[$1])
+      LogicalUnion(all=[true])
+        LogicalProject(EXPR$0=[null:INTEGER], EXPR$1=[ROW(0, 1)])
+          LogicalValues(tuples=[[{ 0 }]])
+        LogicalProject(EXPR$0=[1], EXPR$1=[ROW(0, 2)])
+          LogicalValues(tuples=[[{ 0 }]])
+    LogicalProject(K=[2], T=[ROW(0, 3)])
+      LogicalValues(tuples=[[{ 0 }]])
 ]]>
     </Resource>
   </TestCase>