ListTransientTable.java

/*
 * 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.schema.impl;

import org.apache.calcite.DataContext;
import org.apache.calcite.adapter.java.AbstractQueryableTable;
import org.apache.calcite.linq4j.AbstractEnumerable;
import org.apache.calcite.linq4j.Enumerable;
import org.apache.calcite.linq4j.Enumerator;
import org.apache.calcite.linq4j.Linq4j;
import org.apache.calcite.linq4j.QueryProvider;
import org.apache.calcite.linq4j.Queryable;
import org.apache.calcite.linq4j.function.Experimental;
import org.apache.calcite.linq4j.tree.Expression;
import org.apache.calcite.plan.RelOptCluster;
import org.apache.calcite.plan.RelOptTable;
import org.apache.calcite.prepare.Prepare;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rel.core.TableModify;
import org.apache.calcite.rel.logical.LogicalTableModify;
import org.apache.calcite.rel.type.RelDataType;
import org.apache.calcite.rel.type.RelDataTypeFactory;
import org.apache.calcite.rex.RexNode;
import org.apache.calcite.schema.ModifiableTable;
import org.apache.calcite.schema.ScannableTable;
import org.apache.calcite.schema.SchemaPlus;
import org.apache.calcite.schema.Schemas;
import org.apache.calcite.schema.TransientTable;

import org.checkerframework.checker.nullness.qual.Nullable;

import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * {@link TransientTable} backed by a Java list. It will be automatically added to the
 * current schema when {@link #scan(DataContext)} method gets called.
 *
 * <p>NOTE: The current API is experimental and subject to change without notice.
 */
@Experimental
public class ListTransientTable extends AbstractQueryableTable
    implements TransientTable, ModifiableTable, ScannableTable {
  private static final Type TYPE = Object[].class;
  @SuppressWarnings("rawtypes")
  private final List rows = new ArrayList();
  @SuppressWarnings({"unused", "FieldCanBeLocal"})
  private final String name;
  private final RelDataType protoRowType;

  public ListTransientTable(String name, RelDataType rowType) {
    super(TYPE);
    this.name = name;
    this.protoRowType = rowType;
  }

  @Override public TableModify toModificationRel(
      RelOptCluster cluster,
      RelOptTable table,
      Prepare.CatalogReader catalogReader,
      RelNode child,
      TableModify.Operation operation,
      @Nullable List<String> updateColumnList,
      @Nullable List<RexNode> sourceExpressionList,
      boolean flattened) {
    return LogicalTableModify.create(table, catalogReader, child, operation,
        updateColumnList, sourceExpressionList, flattened);
  }

  @SuppressWarnings("rawtypes")
  @Override public Collection getModifiableCollection() {
    return rows;
  }

  @Override public Enumerable<@Nullable Object[]> scan(DataContext root) {

    final AtomicBoolean cancelFlag = DataContext.Variable.CANCEL_FLAG.get(root);

    return new AbstractEnumerable<@Nullable Object[]>() {
      @Override public Enumerator<@Nullable Object[]> enumerator() {
        return new Enumerator<@Nullable Object[]>() {
          @SuppressWarnings({"rawtypes", "unchecked"})
          private final List list = new ArrayList(rows);
          private int i = -1;

          // TODO cleaner way to handle non-array objects?
          @Override public Object[] current() {
            Object current = list.get(i);
            return current != null && current.getClass().isArray()
                ? (Object[]) current
                : new Object[]{current};
          }

          @Override public boolean moveNext() {
            if (cancelFlag != null && cancelFlag.get()) {
              return false;
            }

            return ++i < list.size();
          }

          @Override public void reset() {
            i = -1;
          }

          @Override public void close() {
          }
        };
      }
    };
  }

  @Override public Expression getExpression(SchemaPlus schema, String tableName,
      @SuppressWarnings("rawtypes") Class clazz) {
    return Schemas.tableExpression(schema, elementType, tableName, clazz);
  }

  @Override public <T> Queryable<T> asQueryable(QueryProvider queryProvider,
                                                SchemaPlus schema, String tableName) {
    return new AbstractTableQueryable<T>(queryProvider, schema, this, tableName) {
      @Override public Enumerator<T> enumerator() {
        //noinspection unchecked
        return (Enumerator<T>) Linq4j.enumerator(rows);
      }
    };
  }

  @Override public RelDataType getRowType(RelDataTypeFactory typeFactory) {
    return typeFactory.copyType(protoRowType);
  }

  @Override public Type getElementType() {
    return TYPE;
  }
}