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 19. With zlib specified, valid values are 1-9. When zstd is specified, valid values are 1-19. | |
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: - none (no compression)- rle_type (run-length encoding compression)- zlib (gzip compression)- zstd (Zstandard compression) | |
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. |
Parent topic: System Catalogs Definitions