feat: introduce SubstraitSchema

Author: vbarua

isthmus/src/main/java/io/substrait/isthmus/calcite/SubstraitSchema.java

@@ -0,0 +1,23 @@
+package io.substrait.isthmus.calcite;
+
+import java.util.Map;
+import org.apache.calcite.schema.Table;
+import org.apache.calcite.schema.impl.AbstractSchema;
+
+/**
+ * Basic {@link AbstractSchema} implementation for associating table names to {@link Table} objects
+ */
+public class SubstraitSchema extends AbstractSchema {
+
+  /** Maps of table names to their associated tables */
+  protected final Map<String, Table> tableMap;
+
+  public SubstraitSchema(Map<String, Table> tableMap) {
+    this.tableMap = tableMap;
+  }
+
+  @Override
+  public Map<String, Table> getTableMap() {
+    return tableMap;
+  }
+}

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

@@ -3,6 +3,7 @@
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
 import com.google.protobuf.TextFormat;
+import io.substrait.isthmus.calcite.SubstraitSchema;
 import io.substrait.plan.ProtoPlanConverter;
 import io.substrait.proto.Expression;
 import io.substrait.proto.Plan;
@@ -13,7 +14,6 @@
 import org.apache.calcite.rel.type.RelDataTypeFactory;
 import org.apache.calcite.schema.Schema;
 import org.apache.calcite.schema.Table;
-import org.apache.calcite.schema.impl.AbstractSchema;
 import org.apache.calcite.schema.impl.AbstractTable;
 import org.apache.calcite.sql.parser.SqlParseException;
 import org.apache.calcite.sql.type.SqlTypeName;
@@ -56,14 +56,7 @@ RelDataType map(RelDataType key, RelDataType value) {
 
   private void test(Table table, String query, String expectedExpressionText)
       throws SqlParseException, IOException {
-    final Schema schema =
-        new AbstractSchema() {
-          @Override
-          protected Map<String, Table> getTableMap() {
-            return Map.of("my_table", table);
-          }
-        };
-
+    final Schema schema = new SubstraitSchema(Map.of("my_table", table));
     final SqlToSubstrait sqlToSubstrait = new SqlToSubstrait();
     Plan plan = sqlToSubstrait.execute(query, "nested", schema);
     Expression obtainedExpression =