feat: support parsing of SQL queries with APPLY

This change adds support for parsing of SQL queries with APPLY (join with
correlated subquery), and to build OuterReferences map of correlated variables
present in the query's join predicates. The OuterRefs will be used while
constructing Substrait plans to bind correlated variables. The change also
adds few example queries which depend on APPLY / LATERAL operators.

This change still does not map calcite-correlated-join to Substrait, as the
spec for APPLY is still not approved. As such, while the parsing of calcite
query plans will succeed after this change, the unit tests and run time
conversion will continue to fail in the final step of building the
Substrait plan. Additional changes are needed to support APPLY.

Refs #substrait-io/substrait/issues/357

isthmus/src/main/java/io/substrait/isthmus/OuterReferenceResolver.java

@@ -7,6 +7,7 @@
 import java.util.Map;
 import org.apache.calcite.rel.RelNode;
 import org.apache.calcite.rel.core.CorrelationId;
+import org.apache.calcite.rel.logical.LogicalCorrelate;
 import org.apache.calcite.rel.logical.LogicalFilter;
 import org.apache.calcite.rel.logical.LogicalProject;
 import org.apache.calcite.rex.*;
@@ -48,6 +49,32 @@ public RelNode visit(LogicalFilter filter) throws RuntimeException {
     return super.visit(filter);
   }
 
+  @Override
+  public RelNode visit(LogicalCorrelate correlate) throws RuntimeException {
+    for (CorrelationId id : correlate.getVariablesSet()) {
+      if (!nestedDepth.containsKey(id)) {
+        nestedDepth.put(id, 0);
+      }
+    }
+
+    apply(correlate.getLeft());
+
+    // Correlated join is a special case. The right-rel is a correlated sub-query but not a REX. So,
+    // the RexVisitor cannot be applied to it to correctly compute the depth map. Hence, we need to
+    // manually compute the depth map for the right-rel.
+    for (Map.Entry<CorrelationId, Integer> entry : nestedDepth.entrySet()) {
+      nestedDepth.put(entry.getKey(), entry.getValue() + 1);
+    }
+
+    apply(correlate.getRight()); // look inside sub-queries
+
+    for (Map.Entry<CorrelationId, Integer> entry : nestedDepth.entrySet()) {
+      nestedDepth.put(entry.getKey(), entry.getValue() - 1);
+    }
+
+    return correlate;
+  }
+
   @Override
   public RelNode visitOther(RelNode other) throws RuntimeException {
     for (RelNode child : other.getInputs()) {

isthmus/src/main/java/io/substrait/isthmus/OuterReferenceResolver.md

@@ -14,7 +14,7 @@ WHERE p_size <
                 AND   PS.ps_suppkey = l.l_suppkey))
 
 
-          Filter     ---  $coor0
+          Filter     ---  $corr0
           /      \ condition
          /  p_size <  RexSubquery
        Scan(P)            |
@@ -23,7 +23,7 @@ WHERE p_size <
                           |
                       Project
                           |
-                        Filter   --- $coor2
+                        Filter   --- $corr2
                         /      \
                        /        \
                 Scan (L)         \

isthmus/src/main/java/io/substrait/isthmus/SqlConverterBase.java

@@ -67,8 +67,11 @@ protected SqlConverterBase(FeatureBoard features) {
               new ProxyingMetadataHandlerProvider(DefaultRelMetadataProvider.INSTANCE);
           return new RelMetadataQuery(handler);
         });
-    parserConfig = SqlParser.Config.DEFAULT.withParserFactory(SqlDdlParserImpl.FACTORY);
     featureBoard = features == null ? FEATURES_DEFAULT : features;
+    parserConfig =
+        SqlParser.Config.DEFAULT
+            .withParserFactory(SqlDdlParserImpl.FACTORY)
+            .withConformance(featureBoard.sqlConformanceMode());
   }
 
   protected static final SimpleExtension.ExtensionCollection EXTENSION_COLLECTION;

isthmus/src/main/java/io/substrait/isthmus/SubstraitRelVisitor.java

@@ -61,6 +61,7 @@
 @SuppressWarnings("UnstableApiUsage")
 @Value.Enclosing
 public class SubstraitRelVisitor extends RelNodeVisitor<Rel, RuntimeException> {
+
   static final org.slf4j.Logger logger =
       org.slf4j.LoggerFactory.getLogger(SubstraitRelVisitor.class);
   private static final FeatureBoard FEATURES_DEFAULT = ImmutableFeatureBoard.builder().build();
@@ -196,6 +197,19 @@ public Rel visit(LogicalJoin join) {
 
   @Override
   public Rel visit(LogicalCorrelate correlate) {
+    // left input of correlated-join is similar to the left input of a logical join
+    apply(correlate.getLeft());
+
+    // right input of correlated-join is similar to a correlated sub-query
+    apply(correlate.getRight());
+
+    var joinType =
+        switch (correlate.getJoinType()) {
+          case INNER -> Join.JoinType.INNER; // corresponds to CROSS APPLY join
+          case LEFT -> Join.JoinType.LEFT; // corresponds to OUTER APPLY join
+          default -> throw new UnsupportedOperationException(
+              "Unsupported correlated join type: " + correlate.getJoinType());
+        };
     return super.visit(correlate);
   }
 

isthmus/src/test/java/io/substrait/isthmus/ApplyJoinPlanTest.java

@@ -0,0 +1,69 @@
+package io.substrait.isthmus;
+
+import org.apache.calcite.adapter.tpcds.TpcdsSchema;
+import org.apache.calcite.sql.parser.SqlParseException;
+import org.apache.calcite.sql.validate.SqlConformanceEnum;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class ApplyJoinPlanTest {
+
+  @Test
+  public void lateralJoinQuery() {
+    TpcdsSchema schema = new TpcdsSchema(1.0);
+    String sql;
+    sql =
+        """
+        SELECT ss_sold_date_sk, ss_item_sk, ss_customer_sk
+        FROM store_sales CROSS JOIN LATERAL
+          (select i_item_sk from item where item.i_item_sk = store_sales.ss_item_sk)""";
+
+    SqlToSubstrait s = new SqlToSubstrait();
+    Assertions.assertThrows(
+        UnsupportedOperationException.class,
+        () -> s.execute(sql, "tpcds", schema),
+        "Lateral join is not supported");
+  }
+
+  @Test
+  public void outerApplyQuery() throws SqlParseException {
+    TpcdsSchema schema = new TpcdsSchema(1.0);
+    String sql;
+    sql =
+        """
+        SELECT ss_sold_date_sk, ss_item_sk, ss_customer_sk
+        FROM store_sales OUTER APPLY
+          (select i_item_sk from item where item.i_item_sk = store_sales.ss_item_sk)""";
+
+    FeatureBoard featureBoard =
+        ImmutableFeatureBoard.builder()
+            .sqlConformanceMode(SqlConformanceEnum.SQL_SERVER_2008)
+            .build();
+    SqlToSubstrait s = new SqlToSubstrait(featureBoard);
+    Assertions.assertThrows(
+        UnsupportedOperationException.class,
+        () -> s.execute(sql, "tpcds", schema),
+        "APPLY is not supported");
+  }
+
+  @Test
+  public void crossApplyQuery() throws SqlParseException {
+    TpcdsSchema schema = new TpcdsSchema(1.0);
+    String sql;
+    sql =
+        """
+        SELECT ss_sold_date_sk, ss_item_sk, ss_customer_sk
+        FROM store_sales CROSS APPLY
+          (select i_item_sk from item where item.i_item_sk = store_sales.ss_item_sk)""";
+
+    FeatureBoard featureBoard =
+        ImmutableFeatureBoard.builder()
+            .sqlConformanceMode(SqlConformanceEnum.SQL_SERVER_2008)
+            .build();
+    SqlToSubstrait s = new SqlToSubstrait(featureBoard);
+    Assertions.assertThrows(
+        UnsupportedOperationException.class,
+        () -> s.execute(sql, "tpcds", schema),
+        "APPLY is not supported");
+  }
+}