STL_ANALYZE_COMPRESSION
Records details for compression analysis operations during COPY or ANALYZE COMPRESSION commands.
This view is visible to all users. Superusers can see all rows; regular users can see only their own data. For more information, see Visibility of data in system tables and views.
Table columns
Column name | Data type | Description |
---|---|---|
userid | integer | The ID of the user who generated the entry. |
start_time | timestamp | The time when the compression analysis operation started. |
xid | bigint | The transaction ID of the compression analysis operation. |
tbl | integer | The table ID of the table that was analyzed. |
tablename | character(128) | The name of the table that was analyzed. |
col | integer | The index of the column in the table that was analyzed to determine the compression encoding. |
old_encoding | character(15) | The encoding type before compression analysis. |
new_encoding | character(15) | The encoding type after compression analysis. |
mode | character(14) | The possible values are:
|
Sample queries
The following example inspects the details of compression analysis on the lineitem
table by the last COPY command run in the same session.
select xid, tbl, btrim(tablename) as tablename, col, old_encoding, new_encoding, mode from stl_analyze_compression where xid = (select xid from stl_query where query = pg_last_copy_id()) order by col; xid | tbl | tablename | col | old_encoding | new_encoding | mode ======+========+===========+=====+=================+=================+============= 8196 | 248126 | lineitem | 0 | mostly32 | mostly32 | ON 8196 | 248126 | lineitem | 1 | mostly32 | lzo | ON 8196 | 248126 | lineitem | 2 | lzo | delta32k | ON 8196 | 248126 | lineitem | 3 | delta | delta | ON 8196 | 248126 | lineitem | 4 | bytedict | bytedict | ON 8196 | 248126 | lineitem | 5 | mostly32 | mostly32 | ON 8196 | 248126 | lineitem | 6 | delta | delta | ON 8196 | 248126 | lineitem | 7 | delta | delta | ON 8196 | 248126 | lineitem | 8 | lzo | zstd | ON 8196 | 248126 | lineitem | 9 | runlength | zstd | ON 8196 | 248126 | lineitem | 10 | delta | lzo | ON 8196 | 248126 | lineitem | 11 | delta | delta | ON 8196 | 248126 | lineitem | 12 | delta | delta | ON 8196 | 248126 | lineitem | 13 | bytedict | zstd | ON 8196 | 248126 | lineitem | 14 | bytedict | zstd | ON 8196 | 248126 | lineitem | 15 | text255 | zstd | ON (16 rows)