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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 typlen in PG_TYPE of 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 -1 on disk. 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 typbyval in PG_TYPE of this column's type
attstorage "char" Copy of typstorage in PG_TYPE of this column's type
attalign "char" Copy of typalign in PG_TYPE 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attisdropped Boolean Indicates that this column has been deleted and is no longer valid.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[] Property-level options
attfdwoptions text[] Property-level external data options
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
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