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. When quicklz1 is specified for compresstype, valid values are 1 or 3. 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)

- 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.

1QuickLZ compression is available only in the commercial release of VMware Greenplum.

Parent topic: System Catalogs Definitions

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