[CALCITE-6575] Refactor SqlValidatorImpl: Add NamespaceBuilder

Adding NamespaceBuilder to formalize the api for customizing/reusing
namespaces downstream.

core/src/main/java/org/apache/calcite/sql/validate/NamespaceBuilder.java

@@ -0,0 +1,195 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to you under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.calcite.sql.validate;
+
+import org.apache.calcite.sql.SqlCall;
+import org.apache.calcite.sql.SqlDelete;
+import org.apache.calcite.sql.SqlInsert;
+import org.apache.calcite.sql.SqlMatchRecognize;
+import org.apache.calcite.sql.SqlMerge;
+import org.apache.calcite.sql.SqlNode;
+import org.apache.calcite.sql.SqlPivot;
+import org.apache.calcite.sql.SqlSelect;
+import org.apache.calcite.sql.SqlUnpivot;
+import org.apache.calcite.sql.SqlUpdate;
+
+import org.checkerframework.checker.initialization.qual.UnknownInitialization;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import static java.util.Objects.requireNonNull;
+
+/**
+ * A builder to allow for customization of namespaces down stream.
+ */
+public class NamespaceBuilder {
+
+  private final SqlValidatorImpl sqlValidatorImpl;
+
+  public NamespaceBuilder(@UnknownInitialization SqlValidatorImpl sqlValidatorImpl) {
+    @SuppressWarnings("argument.type.incompatible")
+    SqlValidatorImpl sqlValidatorCast = sqlValidatorImpl;
+    this.sqlValidatorImpl = sqlValidatorCast;
+  }
+
+  /**
+   * Creates a namespace for a <code>SELECT</code> node. Derived class may
+   * override this factory method.
+   *
+   * @param select        Select node
+   * @param enclosingNode Enclosing node
+   * @return Select namespace
+   */
+  public SelectNamespace createSelectNamespace(
+      SqlSelect select,
+      SqlNode enclosingNode) {
+    return new SelectNamespace(sqlValidatorImpl, select, enclosingNode);
+  }
+
+  /**
+   * Creates a namespace for a set operation (<code>UNION</code>, <code>
+   * INTERSECT</code>, or <code>EXCEPT</code>). Derived class may override
+   * this factory method.
+   *
+   * @param call          Call to set operation
+   * @param enclosingNode Enclosing node
+   * @return Set operation namespace
+   */
+  public SetopNamespace createSetopNamespace(
+      SqlCall call,
+      SqlNode enclosingNode) {
+    return new SetopNamespace(sqlValidatorImpl, call, enclosingNode);
+  }
+
+
+  public MatchRecognizeNamespace createMatchRecognizeNameSpace(
+      SqlMatchRecognize call,
+      SqlNode enclosingNode) {
+    return new MatchRecognizeNamespace(sqlValidatorImpl, call, enclosingNode);
+  }
+
+  public UnpivotNamespace createUnpivotNameSpace(
+      SqlUnpivot call,
+      SqlNode enclosingNode) {
+    return new UnpivotNamespace(sqlValidatorImpl, call, enclosingNode);
+  }
+
+
+  public PivotNamespace createPivotNameSpace(
+      SqlPivot call,
+      SqlNode enclosingNode) {
+    return new PivotNamespace(sqlValidatorImpl, call, enclosingNode);
+  }
+
+  public DmlNamespace createDeleteNamespace(SqlDelete delete,
+      SqlNode enclosingNode, SqlValidatorScope parentScope) {
+    return new DeleteNamespace(sqlValidatorImpl, delete, enclosingNode, parentScope);
+  }
+
+  public DmlNamespace createInsertNamespace(SqlInsert insert,
+      SqlNode enclosingNode, SqlValidatorScope parentScope) {
+    return new InsertNamespace(sqlValidatorImpl, insert, enclosingNode, parentScope);
+  }
+
+  public DmlNamespace createMergeNamespace(SqlMerge merge, SqlNode enclosing,
+      SqlValidatorScope parentScope) {
+    return new MergeNamespace(sqlValidatorImpl, merge, enclosing, parentScope);
+  }
+
+  public DmlNamespace createUpdate(SqlUpdate sqlUpdate, SqlNode enclosing,
+      SqlValidatorScope parentScope) {
+    return new UpdateNamespace(sqlValidatorImpl, sqlUpdate, enclosing, parentScope);
+  }
+
+
+  /**
+   * Common base class for DML statement namespaces.
+   */
+  public abstract static class DmlNamespace extends IdentifierNamespace {
+    protected DmlNamespace(SqlValidatorImpl validator, SqlNode id,
+        SqlNode enclosingNode, SqlValidatorScope parentScope) {
+      super(validator, id, enclosingNode, parentScope);
+    }
+  }
+
+  /**
+   * Namespace for an INSERT statement.
+   */
+  private static class InsertNamespace extends DmlNamespace {
+    private final SqlInsert node;
+
+    InsertNamespace(SqlValidatorImpl validator, SqlInsert node,
+        SqlNode enclosingNode, SqlValidatorScope parentScope) {
+      super(validator, node.getTargetTable(), enclosingNode, parentScope);
+      this.node = requireNonNull(node, "node");
+    }
+
+    @Override public @Nullable SqlNode getNode() {
+      return node;
+    }
+  }
+
+  /**
+   * Namespace for an UPDATE statement.
+   */
+  private static class UpdateNamespace extends DmlNamespace {
+    private final SqlUpdate node;
+
+    UpdateNamespace(SqlValidatorImpl validator, SqlUpdate node,
+        SqlNode enclosingNode, SqlValidatorScope parentScope) {
+      super(validator, node.getTargetTable(), enclosingNode, parentScope);
+      this.node = requireNonNull(node, "node");
+    }
+
+    @Override public @Nullable SqlNode getNode() {
+      return node;
+    }
+  }
+
+  /**
+   * Namespace for a DELETE statement.
+   */
+  private static class DeleteNamespace extends DmlNamespace {
+    private final SqlDelete node;
+
+    DeleteNamespace(SqlValidatorImpl validator, SqlDelete node,
+        SqlNode enclosingNode, SqlValidatorScope parentScope) {
+      super(validator, node.getTargetTable(), enclosingNode, parentScope);
+      this.node = requireNonNull(node, "node");
+    }
+
+    @Override public @Nullable SqlNode getNode() {
+      return node;
+    }
+  }
+
+  /**
+   * Namespace for a MERGE statement.
+   */
+  private static class MergeNamespace extends DmlNamespace {
+    private final SqlMerge node;
+
+    MergeNamespace(SqlValidatorImpl validator, SqlMerge node,
+        SqlNode enclosingNode, SqlValidatorScope parentScope) {
+      super(validator, node.getTargetTable(), enclosingNode, parentScope);
+      this.node = requireNonNull(node, "node");
+    }
+
+    @Override public @Nullable SqlNode getNode() {
+      return node;
+    }
+  }
+}

core/src/main/java/org/apache/calcite/sql/validate/SqlValidator.java

@@ -52,6 +52,7 @@
 import org.apache.calcite.sql.validate.implicit.TypeCoercions;
 
 import org.apiguardian.api.API;
+import org.checkerframework.checker.initialization.qual.UnknownInitialization;
 import org.checkerframework.checker.nullness.qual.Nullable;
 import org.checkerframework.dataflow.qual.Pure;
 import org.immutables.value.Value;
@@ -883,6 +884,15 @@ Config withSqlQueryScopeFactory(
       return SqlQueryScopesImpl::new;
     }
 
+    /** Set a factory for name space builder to allow for custom behavior downstream. */
+    Config withNamespaceBuilderFactory(
+        Function<@UnknownInitialization SqlValidatorImpl, NamespaceBuilder> factory);
+
+    /** Returns a NamespaceBuilder factory. */
+    @Value.Default default Function<@UnknownInitialization SqlValidatorImpl, NamespaceBuilder>
+    namespaceBuilderFactory() {
+      return NamespaceBuilder::new;
+    }
 
     /** Returns the SQL conformance.
      *