The pg_appendonly table contains information about the storage options and other characteristics of append-only tables.

Table 1. pg_catalog.pg_appendonly

column type references description
relid oid   The table object identifier (OID) of the compressed table.
compresslevel smallint   The compression level, with compression ratio increasing from 1 to 9. If zlib is specified, valid values are also 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-only tables. The default is zlib (gzip compression). The quicklz compresstype has been deprecated.
columnstore boolean   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.
version integer   Version of MemTuples and block layout for this table.
pagesize integer   The max page size of this relation. Only valid for Parquet tables; otherwise, the value is 0.
splitsize integer   Size of a split. Default value is 64M, which is controlled by server configuration parameter appendonly_split_write_size_mb.