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 increasing compression ratio. If the gzip or zlib compression type is 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 on append-only and parquet tables. zlib, snappy, and gzip compression types are supported.
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.