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v3.1

Documentation:v3.1

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Row-store Compression System Functions

  • compress_buffer_stat_info()

    Description: Queries the PCA buffer statistics.

    Return type: record

    Table 1 compress_buffer_stat_info parameters

    Parameter Type Parameter Name Type Description
    Output parameter ctrl_cnt bigint pca_page_ctrl_t structure.
    Output parameter main_cnt bigint Total number of main LRU chains in each partition.
    Output parameter free_cnt bigint Total number of free LRU chains in each partition.
    Output parameter recycle_times bigint Number of times that the buffer eliminates LRUs.
  • compress_ratio_info(file_path text)

    Description: Views the file compression rate.

    Return type: record

    Table 2 compress_ratio_info parameters

    Parameter Type Parameter Name Type Description
    Input parameter file_path text Relative file path.
    Output parameter path text Relative path of the file.
    Output parameter is_compress boolean Determines whether the file is a compressed file.
    Output parameter file_count bigint Number of contained segment files.
    Output parameter logic_size bigint Logical size, in bytes.
    Output parameter physic_size bigint Actual physical size, in bytes.
    Output parameter compress_ratio text File compression rate.
  • compress_statistic_info(file_path text, step smallint)

    Description: Collects statistics on the dispersion of compressed files.

    Return type: record

    Table 3 compress_statistic_info parameters

    Parameter Type Parameter Name Type Description
    Input parameter file_path text Relative path of the file.
    Input parameter step smallint Sampling statistics step.
    Output parameter path text Relative path of the file.
    Output parameter extent_count bigint Number of extents.
    Output parameter dispersion_count bigint Number of pages containing discrete chunks.
    Output parameter void_count bigint Number of pages containing unacknowledged chunks.
  • compress_address_header(oid regclass, seg_id bigint)

    Description: Views the management information on the file compression page.

    Return type: record

    Table 4 compress_address_header parameters

    Parameter Type Parameter Name Type Description
    Input parameter oid regclass reloid of the table to which the file belongs.
    Input parameter seg_id bigint Sequence number of a segment file.
    Output parameter extent bigint ID of the extent.
    Output parameter nblocks bigint Number of pages in the extent.
    Output parameter alocated_chunks integer Number of chunks allocated in the extent.
    Output parameter chunk_size integer Chunk size, in bytes.
    Output parameter algorithm bigint Compression algorithm.
  • compress_address_details(oid regclass, seg_id bigint)

    Description: Detailed information about the usage of page chunks.

    Return type: record

    Table 5 compress_address_details parameters

    Parameter Type Parameter Name Type Description
    Input parameter oid regclass reloid of the table to which the file belongs.
    Input parameter seg_id bigint Sequence number of a segment file.
    Output parameter extent bigint ID of the extent.
    Output parameter extent_block_number bigint Page number in the extent. The value ranges from 0 to 127.
    Output parameter block_number bigint Overall page number.
    Output parameter alocated_chunks integer Number of chunks used by the page.
    Output parameter nchunks integer Number of chunks used by the page. The value cannot be greater than the value of alocated_chunks.
    Output parameter chunknos integer Number of the used chunks, starting from 1.
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