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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
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
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package org.apache.impala.analysis;

import org.apache.impala.authorization.Privilege;
import org.apache.impala.common.AnalysisException;
import org.apache.impala.thrift.TFunctionCategory;
import org.apache.impala.thrift.TShowFunctionsParams;

import com.google.common.base.Preconditions;

/**
 * Representation of a SHOW FUNCTIONS [pattern] statement.
 * Acceptable syntax:
 *
 * SHOW FUNCTIONS
 * SHOW FUNCTIONS LIKE 'pattern'
 *
 */
public class ShowFunctionsStmt extends StatementBase {
  // Pattern to match tables against. | denotes choice, * matches all strings
  private final String pattern_;

  // DB (if any) as seen by the parser
  private final String parsedDb_;

  // Category of functions to be shown. Always set.
  private final TFunctionCategory fnCategory_;

  // Set during analysis
  private String postAnalysisDb_;

  /**
   * Constructs a show statement which matches all functions against the
   * supplied pattern.
   */
  public ShowFunctionsStmt(String db, String pattern, TFunctionCategory fnCategory) {
    Preconditions.checkNotNull(fnCategory);
    parsedDb_ = db;
    pattern_ = pattern;
    fnCategory_ = fnCategory;
  }

  /**
   * Can only be called after analysis, returns the name of the database that
   * this show will search against.
   */
  public String getDb() {
    Preconditions.checkNotNull(postAnalysisDb_);
    return postAnalysisDb_;
  }

  public String getPattern() { return pattern_; }

  @Override
  public String toSql(ToSqlOptions options) {
    String fnCategory = (fnCategory_ == null) ? "" : fnCategory_.toString() + " ";
    if (pattern_ == null) {
      return "SHOW " + fnCategory + "FUNCTIONS";
    } else {
      return "SHOW " + fnCategory + "FUNCTIONS LIKE '" + pattern_ + "'";
    }
  }

  @Override
  public void analyze(Analyzer analyzer) throws AnalysisException {
    postAnalysisDb_ = (parsedDb_ == null ? analyzer.getDefaultDb() : parsedDb_);
    if (analyzer.getDb(postAnalysisDb_, Privilege.VIEW_METADATA) == null) {
      throw new AnalysisException(Analyzer.DB_DOES_NOT_EXIST_ERROR_MSG + postAnalysisDb_);
    }
  }

  public TShowFunctionsParams toThrift() {
    TShowFunctionsParams params = new TShowFunctionsParams();
    params.setCategory(fnCategory_);
    params.setDb(getDb());
    params.setShow_pattern(getPattern());
    return params;
  }
}