__gp_aovisimap_compaction_info(oid)

This function displays compaction information for an append-optimized table. The information is for the on-disk data files on Greengage DB segments that store the table data. You can use the information to determine the data files that will be compacted by a VACUUM operation on an append-optimized table.

NOTE

Until a VACUUM operation deletes the row from the data file, deleted or updated data rows occupy physical space on disk even though they are hidden to new transactions. The configuration parameter gp_appendonly_compaction controls the functionality of the VACUUM command.

This table describes the __gp_aovisimap_compaction_info() function output table.

Column Description

Column	Description
content	Greengage DB segment ID
datafile	ID of the data file on the segment
compaction_possible	The value is either `t` or `f`. The value `t` indicates that the data in data file be compacted when a `VACUUM` operation is performed. The server configuration parameter `gp_appendonly_compaction_threshold` affects this value
hidden_tupcount	In the data file, the number of hidden (deleted or updated) rows
total_tupcount	In the data file, the total number of rows
percent_hidden	In the data file, the ratio (as a percentage) of hidden (deleted or updated) rows to total rows

content

Greengage DB segment ID

datafile

ID of the data file on the segment

compaction_possible

The value is either t or f. The value t indicates that the data in data file be compacted when a VACUUM operation is performed.

The server configuration parameter gp_appendonly_compaction_threshold affects this value

hidden_tupcount

In the data file, the number of hidden (deleted or updated) rows

total_tupcount

In the data file, the total number of rows

percent_hidden

In the data file, the ratio (as a percentage) of hidden (deleted or updated) rows to total rows

__gp_aovisimap(regclass)

__gp_aovisimap_entry(regclass)