1 /*-------------------------------------------------------------------------
4 * definition of the "attribute" system catalog (pg_attribute)
6 * The initial contents of pg_attribute are generated at compile time by
7 * genbki.pl, so there is no pg_attribute.dat file. Only "bootstrapped"
8 * relations need be included.
11 * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
12 * Portions Copyright (c) 1994, Regents of the University of California
14 * src/include/catalog/pg_attribute.h
17 * The Catalog.pm module reads this file and derives schema
20 *-------------------------------------------------------------------------
22 #ifndef PG_ATTRIBUTE_H
23 #define PG_ATTRIBUTE_H
25 #include "catalog/genbki.h"
26 #include "catalog/pg_attribute_d.h"
29 * pg_attribute definition. cpp turns this into
30 * typedef struct FormData_pg_attribute
32 * If you change the following, make sure you change the structs for
33 * system attributes in catalog/heap.c also.
34 * You may need to change catalog/genbki.pl as well.
37 CATALOG(pg_attribute,1249,AttributeRelationId) BKI_BOOTSTRAP BKI_ROWTYPE_OID(75,AttributeRelation_Rowtype_Id) BKI_SCHEMA_MACRO
39 Oid attrelid; /* OID of relation containing this attribute */
40 NameData attname; /* name of attribute */
43 * atttypid is the OID of the instance in Catalog Class pg_type that
44 * defines the data type of this attribute (e.g. int4). Information in
45 * that instance is redundant with the attlen, attbyval, and attalign
46 * attributes of this instance, so they had better match or Postgres will
52 * attstattarget is the target number of statistics datapoints to collect
53 * during VACUUM ANALYZE of this column. A zero here indicates that we do
54 * not wish to collect any stats about this column. A "-1" here indicates
55 * that no value has been explicitly set for this column, so ANALYZE
56 * should use the default setting.
58 int32 attstattarget BKI_DEFAULT(-1);
61 * attlen is a copy of the typlen field from pg_type for this attribute.
62 * See atttypid comments above.
67 * attnum is the "attribute number" for the attribute: A value that
68 * uniquely identifies this attribute within its class. For user
69 * attributes, Attribute numbers are greater than 0 and not greater than
70 * the number of attributes in the class. I.e. if the Class pg_class says
71 * that Class XYZ has 10 attributes, then the user attribute numbers in
72 * Class pg_attribute must be 1-10.
74 * System attributes have attribute numbers less than 0 that are unique
75 * within the class, but not constrained to any particular range.
77 * Note that (attnum - 1) is often used as the index to an array.
82 * attndims is the declared number of dimensions, if an array type,
88 * fastgetattr() uses attcacheoff to cache byte offsets of attributes in
89 * heap tuples. The value actually stored in pg_attribute (-1) indicates
90 * no cached value. But when we copy these tuples into a tuple
91 * descriptor, we may then update attcacheoff in the copies. This speeds
92 * up the attribute walking process.
94 int32 attcacheoff BKI_DEFAULT(-1);
97 * atttypmod records type-specific data supplied at table creation time
98 * (for example, the max length of a varchar field). It is passed to
99 * type-specific input and output functions as the third argument. The
100 * value will generally be -1 for types that do not need typmod.
102 int32 atttypmod BKI_DEFAULT(-1);
105 * attbyval is a copy of the typbyval field from pg_type for this
106 * attribute. See atttypid comments above.
111 * attstorage tells for VARLENA attributes, what the heap access
112 * methods can do to it if a given tuple doesn't fit into a page.
113 * Possible values are
114 * 'p': Value must be stored plain always
115 * 'e': Value can be stored in "secondary" relation (if relation
116 * has one, see pg_class.reltoastrelid)
117 * 'm': Value can be stored compressed inline
118 * 'x': Value can be stored compressed inline or in "secondary"
119 * Note that 'm' fields can also be moved out to secondary storage,
120 * but only as a last resort ('e' and 'x' fields are moved first).
126 * attalign is a copy of the typalign field from pg_type for this
127 * attribute. See atttypid comments above.
131 /* This flag represents the "NOT NULL" constraint */
134 /* Has DEFAULT value or not */
135 bool atthasdef BKI_DEFAULT(f);
137 /* Has a missing value or not */
138 bool atthasmissing BKI_DEFAULT(f);
140 /* One of the ATTRIBUTE_IDENTITY_* constants below, or '\0' */
141 char attidentity BKI_DEFAULT('\0');
143 /* One of the ATTRIBUTE_GENERATED_* constants below, or '\0' */
144 char attgenerated BKI_DEFAULT('\0');
146 /* Is dropped (ie, logically invisible) or not */
147 bool attisdropped BKI_DEFAULT(f);
150 * This flag specifies whether this column has ever had a local
151 * definition. It is set for normal non-inherited columns, but also for
152 * columns that are inherited from parents if also explicitly listed in
153 * CREATE TABLE INHERITS. It is also set when inheritance is removed from
154 * a table with ALTER TABLE NO INHERIT. If the flag is set, the column is
155 * not dropped by a parent's DROP COLUMN even if this causes the column's
156 * attinhcount to become zero.
158 bool attislocal BKI_DEFAULT(t);
160 /* Number of times inherited from direct parent relation(s) */
161 int32 attinhcount BKI_DEFAULT(0);
163 /* attribute's collation */
166 #ifdef CATALOG_VARLEN /* variable-length fields start here */
167 /* NOTE: The following fields are not present in tuple descriptors. */
169 /* Column-level access permissions */
170 aclitem attacl[1] BKI_DEFAULT(_null_);
172 /* Column-level options */
173 text attoptions[1] BKI_DEFAULT(_null_);
175 /* Column-level FDW options */
176 text attfdwoptions[1] BKI_DEFAULT(_null_);
179 * Missing value for added columns. This is a one element array which lets
180 * us store a value of the attribute type here.
182 anyarray attmissingval BKI_DEFAULT(_null_);
184 } FormData_pg_attribute;
187 * ATTRIBUTE_FIXED_PART_SIZE is the size of the fixed-layout,
188 * guaranteed-not-null part of a pg_attribute row. This is in fact as much
189 * of the row as gets copied into tuple descriptors, so don't expect you
190 * can access fields beyond attcollation except in a real tuple!
192 #define ATTRIBUTE_FIXED_PART_SIZE \
193 (offsetof(FormData_pg_attribute,attcollation) + sizeof(Oid))
196 * Form_pg_attribute corresponds to a pointer to a tuple with
197 * the format of pg_attribute relation.
200 typedef FormData_pg_attribute *Form_pg_attribute;
202 #ifdef EXPOSE_TO_CLIENT_CODE
204 #define ATTRIBUTE_IDENTITY_ALWAYS 'a'
205 #define ATTRIBUTE_IDENTITY_BY_DEFAULT 'd'
207 #define ATTRIBUTE_GENERATED_STORED 's'
209 #endif /* EXPOSE_TO_CLIENT_CODE */
211 #endif /* PG_ATTRIBUTE_H */