A column with a nonzero number of ancestors cannot be dropped nor renamed.Īttcollation oid (references pg_collation. The number of direct ancestors this column has. Note that a column can be locally defined and inherited simultaneously. This column is defined locally in the relation. A dropped column is still physically present in the table, but is ignored by the parser and so cannot be accessed via SQL. This column has been dropped and is no longer valid. (Other values might be added in the future.) If a zero byte ( ''), then not a generated column. Otherwise, a = generated always, d = generated by default. If a zero byte ( ''), then not an identity column. The actual value used is stored in the attmissingval column. 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. (Check attgenerated to determine whether this is a default or a generation expression.) 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. However, this field is ignored whenever attstorage does not allow compression. Otherwise, 'p' selects pglz compression, while 'l' selects LZ4 compression. Typically this is '\0' to specify use of the current default setting (see default_toast_compression). The current compression method of the column. For TOAST-able data types, this can be altered after column creation to control storage policy. Normally a copy of pg_type.typstorage of this column's type. The value will generally be -1 for types that do not need atttypmod.Ī copy of pg_type.typbyval of this column's typeĪ copy of pg_type.typalign of this column's type It is passed to type-specific input functions and length coercion functions. (Presently, the number of dimensions of an array is not enforced, so any nonzero value effectively means “ it's an array”.)Īlways -1 in storage, but when loaded into a row descriptor in memory this might be updated to cache the offset of the attribute within the rowĪtttypmod records type-specific data supplied at table creation time (for example, the maximum length of a varchar column). Number of dimensions, if the column is an array type otherwise 0. System columns, such as ctid, have (arbitrary) negative numbers. 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.Ī copy of pg_type.typlen of this column's type The exact meaning of positive values is data type-dependent. A negative value says to use the system default statistics target. A zero value indicates that no statistics should be collected. The data type of this column (zero for a dropped column)Īttstattarget controls the level of detail of statistics accumulated for this column by ANALYZE.
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