fe/src/main/java/org/apache/impala/catalog/local/LocalView.java

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// to you under the Apache License, Version 2.0 (the
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//
//   http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.impala.catalog.local;

import java.util.List;
import java.util.Set;

import org.apache.hadoop.hive.metastore.api.Table;
import org.apache.impala.analysis.QueryStmt;
import org.apache.impala.catalog.FeView;
import org.apache.impala.catalog.TableLoadingException;
import org.apache.impala.catalog.View;
import org.apache.impala.catalog.local.MetaProvider.TableMetaRef;
import org.apache.impala.thrift.TCatalogObjectType;
import org.apache.impala.thrift.TTableDescriptor;

/**
 * View implementation corresponding to the LocalCatalog.
 *
 * NOTE: this does _not_ implement "local views" in the sense of a view defined
 * in the scope of a query using a WITH expression.
 */
public class LocalView extends LocalTable implements FeView {
  private final QueryStmt queryStmt_;

  public LocalView(LocalDb db, Table msTbl, TableMetaRef ref) {
    super(db, msTbl, ref);

    try {
      queryStmt_ = View.parseViewDef(this);
    } catch (TableLoadingException e) {
      throw new LocalCatalogException(e);
    }
  }

  @Override
  public TTableDescriptor toThriftDescriptor(int tableId,
      Set<Long> referencedPartitions) {
    // Views are always resolved into underlying tables before being serialized.
    throw new IllegalStateException("Cannot call toThriftDescriptor() on a view.");
  }

  // NOTE: "local view" in this context means "a view defined local to a query"
  // whereas "local" in the class name "LocalView" means "view from the
  // LocalCatalog catalog implementation".
  @Override
  public boolean isLocalView() {
    // TODO: the org.apache.impala.catalog.View class is still used for local views
    // even in the LocalCatalog implementation.
    return false;
  }

  @Override
  public QueryStmt getQueryStmt() {
    return queryStmt_;
  }

  @Override
  public List<String> getColLabels() {
    // Explicit column labels are only used by local views.
    // Returning null indicates that the column labels are derived
    // from the underlying statement.
    return null;
  }

  @Override
  public TCatalogObjectType getCatalogObjectType() {
    return TCatalogObjectType.VIEW;
  }
}