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.