pg_appendonly

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	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`.