pg_attribute

The pg_attribute table stores information about table columns. There will be exactly one pg_attribute row for every column in every table in the database. There will also be attribute entries for indexes, and all objects that have pg_class entries. The term attribute is equivalent to column.

Column Type References Description

Column	Type	References	Description
attrelid	oid	pg_class.oid	The table this column belongs to
attname	name	—	The column name
atttypid	oid	pg_type.oid	The data type of this column
attstattarget	integer	—	Controls the level of detail of statistics accumulated for this column by `ANALYZE`. A zero value indicates that no statistics should be collected. A negative value says to use the system default statistics target. The exact meaning of positive values is data type-dependent. For scalar data types, it is both the target number of "most common values" to collect and the target number of histogram bins to create
attlen	int2	—	A copy of `pg_type.typlen` of this column’s type
attnum	int2	—	The number of the column. Ordinary columns are numbered from 1 up. System columns, such as `oid`, have (arbitrary) negative numbers
attndims	integer	—	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 is an array
attcacheoff	integer	—	Always `-1` in storage, but when loaded into a row descriptor in memory this may be updated to cache the offset of the attribute within the row
atttypmod	integer	—	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 it
attbyval	boolean	—	A copy of `pg_type.typbyval` of this column’s type
attstorage	char	—	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
attalign	char	—	A copy of `pg_type.typalign` of this column’s type
attnotnull	boolean	—	This represents a not-null constraint. It is possible to change this column to activate or deactivate the constraint
atthasdef	boolean	—	This column has a default value, in which case there will be a corresponding entry in the `pg_attrdef` catalog that actually defines the value
attisdropped	boolean	—	This column has been dropped and is no longer valid.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	boolean	—	This column is defined locally in the relation. Note that a column may be locally defined and inherited simultaneously
attinhcount	integer	—	The number of direct descendants this column has. A column with a nonzero number of descendants cannot be dropped nor renamed
attcollation	oid	pg_collation.oid	The defined collation of the column, or `0` if it is not of a collatable data type
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

attrelid

oid

pg_class.oid

The table this column belongs to

attname

name

—

The column name

atttypid

oid

pg_type.oid

The data type of this column

attstattarget

integer

—

Controls the level of detail of statistics accumulated for this column by ANALYZE. A zero value indicates that no statistics should be collected. A negative value says to use the system default statistics target. The exact meaning of positive values is data type-dependent. For scalar data types, it is both the target number of "most common values" to collect and the target number of histogram bins to create

attlen

int2

—

A copy of pg_type.typlen of this column’s type

attnum

int2

—

The number of the column. Ordinary columns are numbered from 1 up. System columns, such as oid, have (arbitrary) negative numbers

attndims

integer

—

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 is an array

attcacheoff

integer

—

Always -1 in storage, but when loaded into a row descriptor in memory this may be updated to cache the offset of the attribute within the row

atttypmod

integer

—

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 it

attbyval

boolean

—

A copy of pg_type.typbyval of this column’s type

attstorage

char

—

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

attalign

char

—

A copy of pg_type.typalign of this column’s type

attnotnull

boolean

—

This represents a not-null constraint. It is possible to change this column to activate or deactivate the constraint

atthasdef

boolean

—

This column has a default value, in which case there will be a corresponding entry in the pg_attrdef catalog that actually defines the value

attisdropped

boolean

—

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

boolean

—

This column is defined locally in the relation. Note that a column may be locally defined and inherited simultaneously

attinhcount

integer

—

The number of direct descendants this column has. A column with a nonzero number of descendants cannot be dropped nor renamed

attcollation

oid

pg_collation.oid

The defined collation of the column, or 0 if it is not of a collatable data type

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

pg_attrdef

pg_attribute_encoding