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From omalley <...@git.apache.org>
Subject [GitHub] orc pull request #41: ORC-58: Move code for reading rows from Reader to RowR...
Date Tue, 19 Jul 2016 16:52:13 GMT
Github user omalley commented on a diff in the pull request:

    https://github.com/apache/orc/pull/41#discussion_r71378147
  
    --- Diff: c++/include/orc/Reader.hh ---
    @@ -645,7 +645,72 @@ namespace orc {
       };
     
       /**
    -   * The interface for reading ORC files.
    +   * The interface for reading rows in ORC files.
    +   * This is an an abstract class that will subclassed as necessary.
    +   */
    +  class RowReader {
    +  public:
    +    virtual ~RowReader();
    +    /**
    +     * Get the selected type of the rows in the file. The file's row type
    +     * is projected down to just the selected columns. Thus, if the file's
    +     * type is struct<col0:int,col1:double,col2:string> and the selected
    +     * columns are "col0,col2" the selected type would be
    +     * struct<col0:int,col2:string>.
    +     * @return the root type
    +     */
    +    virtual const Type& getSelectedType() const = 0;
    +
    +    /**
    +     * Get the selected columns of the file.
    +     */
    +    virtual const std::vector<bool> getSelectedColumns() const = 0;
    +
    +    /**
    +     * Create a row batch for reading the selected columns of this file.
    +     * @param size the number of rows to read
    +     * @return a new ColumnVectorBatch to read into
    +     */
    +    virtual ORC_UNIQUE_PTR<ColumnVectorBatch> createRowBatch(uint64_t size
    +                                                             ) const = 0;
    +
    +    /**
    +     * Read the next row batch from the current position.
    +     * Caller must look at numElements in the row batch to determine how
    +     * many rows were read.
    +     * @param data the row batch to read into.
    +     * @return true if a non-zero number of rows were read or false if the
    +     *   end of the file was reached.
    +     */
    +    virtual bool next(ColumnVectorBatch& data) = 0;
    +
    +    /**
    +     * Get the row number of the first row in the previously read batch.
    +     * @return the row number of the previous batch.
    +     */
    +    virtual uint64_t getRowNumber() const = 0;
    +
    +    /**
    +     * Seek to a given row.
    +     * @param rowNumber the next row the reader should return
    +     */
    +    virtual void seekToRow(uint64_t rowNumber) = 0;
    +  
    +    /**
    +     * Estimate an upper bound on heap memory allocation by the Reader
    +     * based on the information in the file footer.
    +     * The bound is less tight if only few columns are read or compression is
    +     * used.
    +     * @param stripeIx index of the stripe to be read (if not specified,
    +     *        all stripes are considered).
    +     * @return upper bound on memory use
    +     */
    +    virtual uint64_t getMemoryUse(int stripeIx=-1) = 0;
    --- End diff --
    
    This should stay in the reader.


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