pg_appendonly
The pg_appendonly table contains information about the storage options and other characteristics of append-optimized tables.
| column | type | references | description |
|---|---|---|---|
relid |
oid | The table object identifier (OID) of the compressed table. | |
blocksize |
integer | Block size used for compression of append-optimized tables. Valid values are 8K - 2M. Default is 32K. |
|
safefswritesize |
integer | Minimum size for safe write operations to append-optimized tables in a non-mature file system. Commonly set to a multiple of the extent size of the file system; for example, Linux ext3 is 4096 bytes, so a value of 32768 is commonly used. | |
compresslevel |
smallint | The compression level, with compression ratio increasing from 1 to 9. When quicklz1 is specified for compresstype, valid values are 1 or 3. With zlib specified, valid values are 1-9. |
|
majorversion |
smallint | The major version number of the pg_appendonly table. | |
minorversion |
smallint | The minor version number of the pg_appendonly table. | |
checksum |
boolean | A checksum value that is stored to compare the state of a block of data at compression time and at scan time to ensure data integrity. | |
compresstype |
text | Type of compression used to compress append-optimized tables. Valid values are zlib (gzip compression) and quicklz1 |
|
columnstore |
boolean | 1 for column-oriented storage, 0 for row-oriented storage. |
|
segrelid |
oid | Table on-disk segment file id. | |
segidxid |
oid | Index on-disk segment file id. | |
blkdirrelid |
oid | Block used for on-disk column-oriented table file. | |
blkdiridxid |
oid | Block used for on-disk column-oriented index file. | |
visimaprelid |
oid | Visibility map for the table. | |
visimapidxid |
oid | B-tree index on the visibility map. |
Note: 1QuickLZ compression is available only in the commercial release of Tanzu Greenplum.
Parent topic: System Catalogs Definitions
