PG_ATTRIBUTE

PG_ATTRIBUTE records information about table columns.

**Table 1** PG_ATTRIBUTE columns
Name	Type	Description
attrelid	oid	Table to which a column belongs
attname	name	Column name
atttypid	oid	Column type
attstattarget	integer	Level of details of statistics collected for this column by ANALYZE. The value 0 indicates that no statistics should be collected. A negative value indicates that the system default statistic object is used. 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.
attlen	smallint	Copy of pg_type.typlen in the column's type
attnum	smallint	Number of the column
attndims	integer	Number of dimensions if the column is an array (0 in other cases)
attcacheoff	integer	This column is always set to –1 on disks. When it is loaded into a row descriptor in the memory, it may be updated to cache the offset of the columns in the row.
atttypmod	integer	Type-specific data supplied at the table creation time (for example, the maximum length of a varchar column). This column is used as the third parameter when passing to type-specific input functions and length coercion functions. The value will generally be –1 for types that do not need atttypmod.
attbyval	boolean	Copy of pg_type.typbyval of this column's type
attstorage	"char"	Copy of pg_type.typstorage of this column's type
attalign	"char"	Copy of pg_type.typalign of this column's type
attnotnull	boolean	A non-null constraint. It is possible to change this column to enable or disable the constraint.
atthasdef	boolean	This column has a default value, in which case there will be a corresponding entry in the PG_ATTRDEF table that actually defines the value.
attisdropped	boolean	Indicates that this column has been deleted and is no longer valid. A deleted column is still physically present in the table but is ignored by the analyzer, so it cannot be accessed through SQL.
attislocal	boolean	Indicates that this column is locally defined in the relationship. Note that a column can be locally defined and inherited simultaneously.
attcmprmode	tinyint	Compressed modes for a specific column. The compressed mode includes: ATT_CMPR_NOCOMPRESS ATT_CMPR_DELTA ATT_CMPR_DICTIONARY ATT_CMPR_PREFIX ATT_CMPR_NUMSTR
attinhcount	integer	Number of direct ancestors that this column has. A column with an ancestor cannot be dropped nor renamed.
attcollation	oid	Defined collation of a column
attacl	aclitem[]	Permissions for column-level access
attoptions	text[]	Column attribute. Currently, the following attributes are supported: n_distinct: number of distinct values of a column (excluding subtables). n_distinct_inherited: number of distinct values of a column (including subtables).
attfdwoptions	text[]	Column attribute of a foreign table. Currently, dist_fdw, file_fdw, and log_fdw do not use foreign table column attributes.
attinitdefval	bytea	attinitdefval stores the default value expression. ADD COLUMN in the row-store table must use this column.
attkvtype	tinyint	Specifies the key value type for a column. Value: 0. ATT_KV_UNDEFINED: default value 1. ATT_KV_TAG: dimension 2. ATT_KV_FIELD: indicator 3. ATT_KV_TIMETAG: time column