pg_attribute

The catalog pg_attribute stores information about table columns.

Reading PG 18current·documented in 24 of 24 versions, 7.4 to 20

7.4 8.0 8.1 8.2 8.3 8.4 9.0 9.1 9.2 9.3 9.4 9.5 9.6 10 11 12 13 14 15 16 17 18 19 20

Kind: System catalogs
Columns in this snapshot: 25
Definition source: English manual
Metadata snapshot: 18.6

Columns 25

As listed in the PostgreSQL 18 manual.

Column	Type	Description / reference
`attrelid`	`oid`NOT NULL	The table this column belongs to pg_class.oid
`attname`	`name`NOT NULL	The column name
`atttypid`	`oid`NOT NULL	The data type of this column (zero for a dropped column) pg_type.oid
`attlen`	`int2`NOT NULL	A copy of pg_type.typlen of this column's type
`attnum`	`int2`NOT NULL	The number of the column. Ordinary columns are numbered from 1 up. System columns, such as ctid, have (arbitrary) negative numbers.
`atttypmod`	`int4`NOT NULL	atttypmod records type-specific data supplied at table creation time (for example, the maximum length of a varchar column). It is passed to type-specific input functions and length coercion functions. The value will generally be -1 for types that do not need atttypmod.
`attndims`	`int2`NOT NULL	Number of dimensions, if the column is an array type; otherwise 0. (Presently, the number of dimensions of an array is not enforced, so any nonzero value effectively means “it's an array”.)
`attbyval`	`bool`NOT NULL	A copy of pg_type.typbyval of this column's type
`attalign`	`char`NOT NULL	A copy of pg_type.typalign of this column's type
`attstorage`	`char`NOT NULL	Normally a copy of pg_type.typstorage of this column's type. For TOAST-able data types, this can be altered after column creation to control storage policy.
`attcompression`	`char`NOT NULL	The current compression method of the column. Typically this is '\0' to specify use of the current default setting (see default_toast_compression). Otherwise, 'p' selects pglz compression, while 'l' selects LZ4 compression. However, this field is ignored whenever attstorage does not allow compression.
`attnotnull`	`bool`NOT NULL	This column has a (possibly invalid) not-null constraint.
`atthasdef`	`bool`NOT NULL	This column has a default expression or generation expression, in which case there will be a corresponding entry in the pg_attrdef catalog that actually defines the expression. (Check attgenerated to determine whether this is a default or a generation expression.)
`atthasmissing`	`bool`NOT NULL	This column has a value which is used where the column is entirely missing from the row, as happens when a column is added with a non-volatile DEFAULT value after the row is created. The actual value used is stored in the attmissingval column.
`attidentity`	`char`NOT NULL	If a zero byte (''), then not an identity column. Otherwise, a = generated always, d = generated by default.
`attgenerated`	`char`NOT NULL	If a zero byte (''), then not a generated column. Otherwise, s = stored, v = virtual. A stored generated column is physically stored like a normal column. A virtual generated column is physically stored as a null value, with the actual value being computed at run time.
`attisdropped`	`bool`NOT NULL	This column has been dropped and is no longer valid. A dropped column is still physically present in the table, but is ignored by the parser and so cannot be accessed via SQL.
`attislocal`	`bool`NOT NULL	This column is defined locally in the relation. Note that a column can be locally defined and inherited simultaneously.
`attinhcount`	`int2`NOT NULL	The number of direct ancestors this column has. A column with a nonzero number of ancestors cannot be dropped nor renamed.
`attcollation`	`oid`NOT NULL	The defined collation of the column, or zero if the column is not of a collatable data type pg_collation.oid
`attstattarget`	`int2`	attstattarget controls the level of detail of statistics accumulated for this column by ANALYZE. A zero value indicates that no statistics should be collected. A null value says to use the system default statistics target. The exact meaning of positive values is data type-dependent. For scalar data types, attstattarget is both the target number of “most common values” to collect, and the target number of histogram bins to create.
`attacl`	`aclitem[]`	Column-level access privileges, if any have been granted specifically on this column
`attoptions`	`text[]`	Attribute-level options, as “keyword=value” strings
`attfdwoptions`	`text[]`	Attribute-level foreign data wrapper options, as “keyword=value” strings
`attmissingval`	`anyarray`	This column has a one element array containing the value used when the column is entirely missing from the row, as happens when the column is added with a non-volatile DEFAULT value after the row is created. The value is only used when atthasmissing is true. If there is no value the column is null.