pg_attribute
The catalog pg_attribute 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 indeed all objects that have pg_class entries.) The term attribute is equivalent to column and is used for historical reasons.
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Definition PG 18
The catalog pg_attribute 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 indeed all objects that have pg_class entries.) The term attribute is equivalent to column and is used for historical reasons.
Catalog columns
| Column | Type | Nullability | Description |
|---|---|---|---|
| attrelid | oid | Not null | The table this column belongs to |
| attname | name | Not null | The column name |
| atttypid | oid | Not null | The data type of this column (zero for a dropped column) |
| 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 |
| attstattarget | int2 | Nullable | 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[] | Nullable | Column-level access privileges, if any have been granted specifically on this column |
| attoptions | text[] | Nullable | Attribute-level options, as “keyword=value” strings. Can also contain some internal options prefixed with pg_, which cannot be set via DDL. Currently the only internal option is pg_attver. |
| attfdwoptions | text[] | Nullable | Attribute-level foreign data wrapper options, as “keyword=value” strings |
| attmissingval | anyarray | Nullable | 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. |
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attrelid, attname, atttypid, attlen, attnum, atttypmod, attndims, attbyval, attalign, attstorage, attcompression, attnotnull, atthasdef, atthasmissing, attidentity, attgenerated, attisdropped, attislocal, attinhcount, attcollation, attstattarget, attacl, attoptions, attfdwoptions, attmissingval
Source references
Full definition and evidence JSON
Definition sources
center · PostgreSQL 18 · catalog-bilingual-repair:5f3d21cc11e795731c475667f9045e714fba547de9b4d24754f861d1b07ac4f1
Text language: en · catalog-bilingual-repair:5f3d21cc11e795731c475667f9045e714fba547de9b4d24754f861d1b07ac4f1