fe/src/main/java/org/apache/impala/common/TableAliasGenerator.java

// Licensed to the Apache Software Foundation (ASF) under one
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// distributed with this work for additional information
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// 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
//
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package org.apache.impala.common;

import org.apache.impala.analysis.Analyzer;

import com.google.common.base.Preconditions;

public class TableAliasGenerator extends AliasGenerator {
  private static final String DEFAULT_TBL_ALIAS_PREFIX = "$a$";

  public TableAliasGenerator(Analyzer analyzer, String prefix) {
    Preconditions.checkNotNull(analyzer);
    aliasPrefix_ = prefix != null ? prefix : DEFAULT_TBL_ALIAS_PREFIX;
    Analyzer currentAnalyzer = analyzer;
    do {
      usedAliases_.addAll(currentAnalyzer.getAliases());
      usedAliases_.addAll(currentAnalyzer.getLocalViews().keySet());
      currentAnalyzer = currentAnalyzer.getParentAnalyzer();
    } while (currentAnalyzer != null);
  }
}