[CALCITE-5251] Support SQL hint for Snapshot

core/src/main/java/org/apache/calcite/rel/core/Snapshot.java

@@ -21,12 +21,16 @@
 import org.apache.calcite.rel.RelNode;
 import org.apache.calcite.rel.RelWriter;
 import org.apache.calcite.rel.SingleRel;
+import org.apache.calcite.rel.hint.Hintable;
+import org.apache.calcite.rel.hint.RelHint;
 import org.apache.calcite.rel.type.RelDataType;
 import org.apache.calcite.rex.RexNode;
 import org.apache.calcite.rex.RexShuttle;
 import org.apache.calcite.sql.type.SqlTypeName;
 import org.apache.calcite.util.Litmus;
 
+import com.google.common.collect.ImmutableList;
+
 import org.checkerframework.checker.nullness.qual.Nullable;
 
 import java.util.List;
@@ -43,30 +47,49 @@
  * returns the contents whose versions that overlap with the given specific
  * period (i.e. those that started before given period and ended after it).
  */
-public abstract class Snapshot extends SingleRel  {
+public abstract class Snapshot extends SingleRel implements Hintable {
   //~ Instance fields --------------------------------------------------------
 
   private final RexNode period;
 
+  protected final ImmutableList<RelHint> hints;
+
   //~ Constructors -----------------------------------------------------------
 
   /**
    * Creates a Snapshot.
    *
    * @param cluster   Cluster that this relational expression belongs to
    * @param traitSet  The traits of this relational expression
+   * @param hints     Hints for this node
    * @param input     Input relational expression
    * @param period    Timestamp expression which as the table was at the given
    *                  time in the past
    */
   @SuppressWarnings("method.invocation.invalid")
-  protected Snapshot(RelOptCluster cluster, RelTraitSet traitSet, RelNode input,
-      RexNode period) {
+  protected Snapshot(RelOptCluster cluster, RelTraitSet traitSet, List<RelHint> hints,
+      RelNode input, RexNode period) {
     super(cluster, traitSet, input);
     this.period = Objects.requireNonNull(period, "period");
+    this.hints = ImmutableList.copyOf(hints);
     assert isValid(Litmus.THROW, null);
   }
 
+  /**
+   * Creates a Snapshot.
+   *
+   * @param cluster   Cluster that this relational expression belongs to
+   * @param traitSet  The traits of this relational expression
+   * @param input     Input relational expression
+   * @param period    Timestamp expression which as the table was at the given
+   *                  time in the past
+   */
+  @SuppressWarnings("method.invocation.invalid")
+  protected Snapshot(
+      RelOptCluster cluster, RelTraitSet traitSet, RelNode input, RexNode period) {
+    this(cluster, traitSet, ImmutableList.of(), input, period);
+  }
+
   //~ Methods ----------------------------------------------------------------
 
   @Override public final RelNode copy(RelTraitSet traitSet, List<RelNode> inputs) {
@@ -100,4 +123,8 @@ public RexNode getPeriod() {
     }
     return litmus.succeed();
   }
+
+  @Override public ImmutableList<RelHint> getHints() {
+    return hints;
+  }
 }

core/src/main/java/org/apache/calcite/rel/hint/HintPredicates.java

@@ -80,6 +80,11 @@ public abstract class HintPredicates {
   public static final HintPredicate WINDOW =
       new NodeTypeHintPredicate(NodeTypeHintPredicate.NodeType.WINDOW);
 
+  /** A hint predicate that indicates a hint can only be used to
+   * {@link org.apache.calcite.rel.core.Snapshot} nodes. */
+  public static final HintPredicate SNAPSHOT =
+      new NodeTypeHintPredicate(NodeTypeHintPredicate.NodeType.SNAPSHOT);
+
   /**
    * Returns a composed hint predicate that represents a short-circuiting logical
    * AND of an array of hint predicates {@code hintPredicates}.  When evaluating the composed

core/src/main/java/org/apache/calcite/rel/hint/NodeTypeHintPredicate.java

@@ -24,6 +24,7 @@
 import org.apache.calcite.rel.core.Join;
 import org.apache.calcite.rel.core.Project;
 import org.apache.calcite.rel.core.SetOp;
+import org.apache.calcite.rel.core.Snapshot;
 import org.apache.calcite.rel.core.Sort;
 import org.apache.calcite.rel.core.TableScan;
 import org.apache.calcite.rel.core.Values;
@@ -99,7 +100,12 @@ enum NodeType {
     /**
      * The hint would be propagated to the Window nodes.
      */
-    WINDOW(Window.class);
+    WINDOW(Window.class),
+
+    /**
+     * The hint would be propagated to the Snapshot nodes.
+     */
+    SNAPSHOT(Snapshot.class);
 
     /** Relational expression clazz that the hint can apply to. */
     @SuppressWarnings("ImmutableEnumChecker")

core/src/main/java/org/apache/calcite/rel/logical/LogicalSnapshot.java

@@ -23,18 +23,39 @@
 import org.apache.calcite.rel.RelDistributionTraitDef;
 import org.apache.calcite.rel.RelNode;
 import org.apache.calcite.rel.core.Snapshot;
+import org.apache.calcite.rel.hint.RelHint;
 import org.apache.calcite.rel.metadata.RelMdCollation;
 import org.apache.calcite.rel.metadata.RelMdDistribution;
 import org.apache.calcite.rel.metadata.RelMetadataQuery;
 import org.apache.calcite.rex.RexNode;
 
+import com.google.common.collect.ImmutableList;
+
+import java.util.List;
+
 /**
  * Sub-class of {@link org.apache.calcite.rel.core.Snapshot}
  * not targeted at any particular engine or calling convention.
  */
 public class LogicalSnapshot extends Snapshot {
 
   //~ Constructors -----------------------------------------------------------
+  /**
+   * Creates a LogicalSnapshot.
+   *
+   * <p>Use {@link #create} unless you know what you're doing.
+   *
+   * @param cluster   Cluster that this relational expression belongs to
+   * @param traitSet  The traits of this relational expression
+   * @param hints     Hints for this node
+   * @param input     Input relational expression
+   * @param period    Timestamp expression which as the table was at the given
+   *                  time in the past
+   */
+  public LogicalSnapshot(RelOptCluster cluster, RelTraitSet traitSet, List<RelHint> hints,
+      RelNode input, RexNode period) {
+    super(cluster, traitSet, hints, input, period);
+  }
 
   /**
    * Creates a LogicalSnapshot.
@@ -49,12 +70,12 @@ public class LogicalSnapshot extends Snapshot {
    */
   public LogicalSnapshot(RelOptCluster cluster, RelTraitSet traitSet,
       RelNode input, RexNode period) {
-    super(cluster, traitSet, input, period);
+    super(cluster, traitSet, ImmutableList.of(), input, period);
   }
 
   @Override public Snapshot copy(RelTraitSet traitSet, RelNode input,
       RexNode period) {
-    return new LogicalSnapshot(getCluster(), traitSet, input, period);
+    return new LogicalSnapshot(getCluster(), traitSet, hints, input, period);
   }
 
   /** Creates a LogicalSnapshot. */
@@ -69,4 +90,8 @@ public static LogicalSnapshot create(RelNode input, RexNode period) {
             () -> RelMdDistribution.snapshot(mq, input));
     return new LogicalSnapshot(cluster, traitSet, input, period);
   }
+
+  @Override public RelNode withHints(final List<RelHint> hintList) {
+    return new LogicalSnapshot(getCluster(), traitSet, hintList, input, getPeriod());
+  }
 }

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

@@ -242,6 +242,13 @@ public final Fixture sql(String sql) {
     sql(sql).ok();
   }
 
+  @Test void testSnapshotHints() {
+    final String sql = "select /*+ fast_snapshot(products_temporal) */ stream * from\n"
+        + " orders join products_temporal for system_time as of timestamp '2022-08-11 15:00:00'\n"
+        + " on orders.productid = products_temporal.productid";
+    sql(sql).ok();
+  }
+
   @Test void testHintsInSubQueryWithDecorrelation() {
     final String sql = "select /*+ resource(parallelism='3'), AGG_STRATEGY(TWO_PHASE) */\n"
         + "sum(e1.empno) from emp e1, dept d1\n"
@@ -889,6 +896,11 @@ private static class HintCollector extends RelShuttleImpl {
           if (window.getHints().size() > 0) {
             this.hintsCollect.add("Window:" + window.getHints());
           }
+        } else if (other instanceof Snapshot) {
+          Snapshot snapshot = (Snapshot) other;
+          if (snapshot.getHints().size() > 0) {
+            this.hintsCollect.add("Snapshot:" + snapshot.getHints());
+          }
         }
         return super.visit(other);
       }
@@ -978,6 +990,7 @@ static HintStrategyTable createHintStrategies(HintStrategyTable.Builder builder)
         .hintStrategy("async_merge", HintPredicates.SORT)
         .hintStrategy("mini_batch",
                 HintPredicates.and(HintPredicates.WINDOW, HintPredicates.PROJECT))
+        .hintStrategy("fast_snapshot", HintPredicates.SNAPSHOT)
         .hintStrategy("use_merge_join",
             HintStrategy.builder(
                 HintPredicates.and(HintPredicates.JOIN, joinWithFixedTableName()))

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

@@ -200,9 +200,8 @@ EnumerableProject(ENAME=[$3], JOB=[$4], SAL=[$7], NAME=[$1])
   </TestCase>
   <TestCase name="testHintsPropagationInVolcanoPlannerRules2">
     <Resource name="sql">
-      <![CDATA[select /*+ my_hint */ ename, job
-from emp where not exists (select 1 from dept where emp.deptno = dept.deptno)
-]]>
+      <![CDATA[select /*+ no_hash_join */ ename, job
+from emp where not exists (select 1 from dept where emp.deptno = dept.deptno)]]>
     </Resource>
     <Resource name="planBefore">
       <![CDATA[
@@ -232,9 +231,8 @@ EnumerableProject(ENAME=[$0], JOB=[$1])
   </TestCase>
   <TestCase name="testHintsPropagationInVolcanoPlannerRules3">
     <Resource name="sql">
-      <![CDATA[select /*+ my_hint */ ename, job
-from emp where not exists (select 1 from dept where emp.deptno = dept.deptno) order by ename
-]]>
+      <![CDATA[select /*+ no_hash_join */ ename, job
+from emp where not exists (select 1 from dept where emp.deptno = dept.deptno) order by ename]]>
     </Resource>
     <Resource name="planBefore">
       <![CDATA[
@@ -358,6 +356,19 @@ on emp.deptno = dept.deptno]]>
 Project:[[PROPERTIES inheritPath:[] options:{K1=v1, K2=v2}]]
 TableScan:[[INDEX inheritPath:[] options:[IDX1, IDX2]], [PROPERTIES inheritPath:[0, 0] options:{K1=v1, K2=v2}]]
 TableScan:[[PROPERTIES inheritPath:[] options:{K1=v1, K2=v2}], [PROPERTIES inheritPath:[0, 1] options:{K1=v1, K2=v2}]]
+]]>
+    </Resource>
+  </TestCase>
+  <TestCase name="testSnapshotHints">
+    <Resource name="sql">
+      <![CDATA[select /*+ fast_snapshot(products_temporal) */ stream * from
+ orders join products_temporal for system_time as of timestamp '2022-08-11 15:00:00'
+ on orders.productid = products_temporal.productid]]>
+    </Resource>
+    <Resource name="hints">
+      <![CDATA[
+Project:[[FAST_SNAPSHOT inheritPath:[] options:[PRODUCTS_TEMPORAL]]]
+Snapshot:[[FAST_SNAPSHOT inheritPath:[0, 1] options:[PRODUCTS_TEMPORAL]]]
 ]]>
     </Resource>
   </TestCase>