src/include/catalog/pg_description.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * pg_description.h
   4  *        definition of the "description" system catalog (pg_description)
   5  *
   6  * Because the contents of this table are taken from the *.dat files
   7  * of other catalogs, there is no pg_description.dat file. The initial
   8  * contents are assembled by genbki.pl and loaded during initdb.
   9  *
  10  * NOTE: an object is identified by the OID of the row that primarily
  11  * defines the object, plus the OID of the table that that row appears in.
  12  * For example, a function is identified by the OID of its pg_proc row
  13  * plus the pg_class OID of table pg_proc.  This allows unique identification
  14  * of objects without assuming that OIDs are unique across tables.
  15  *
  16  * Since attributes don't have OIDs of their own, we identify an attribute
  17  * comment by the objoid+classoid of its parent table, plus an "objsubid"
  18  * giving the attribute column number.  "objsubid" must be zero in a comment
  19  * for a table itself, so that it is distinct from any column comment.
  20  * Currently, objsubid is unused and zero for all other kinds of objects,
  21  * but perhaps it might be useful someday to associate comments with
  22  * constituent elements of other kinds of objects (arguments of a function,
  23  * for example).
  24  *
  25  *
  26  * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
  27  * Portions Copyright (c) 1994, Regents of the University of California
  28  *
  29  * src/include/catalog/pg_description.h
  30  *
  31  * NOTES
  32  *        The Catalog.pm module reads this file and derives schema
  33  *        information.
  34  *
  35  *-------------------------------------------------------------------------
  36  */
  37 #ifndef PG_DESCRIPTION_H
  38 #define PG_DESCRIPTION_H
  39
  40 #include "catalog/genbki.h"
  41 #include "catalog/pg_description_d.h"   /* IWYU pragma: export */
  42
  43 /* ----------------
  44  *              pg_description definition.  cpp turns this into
  45  *              typedef struct FormData_pg_description
  46  * ----------------
  47  */
  48 CATALOG(pg_description,2609,DescriptionRelationId)
  49 {
  50         Oid                     objoid;                 /* OID of object itself */
  51         Oid                     classoid;               /* OID of table containing object */
  52         int32           objsubid;               /* column number, or 0 if not used */
  53
  54 #ifdef CATALOG_VARLEN                   /* variable-length fields start here */
  55         text            description BKI_FORCE_NOT_NULL; /* description of object */
  56 #endif
  57 } FormData_pg_description;
  58
  59 /* ----------------
  60  *              Form_pg_description corresponds to a pointer to a tuple with
  61  *              the format of pg_description relation.
  62  * ----------------
  63  */
  64 typedef FormData_pg_description * Form_pg_description;
  65
  66 DECLARE_TOAST(pg_description, 2834, 2835);
  67
  68 DECLARE_UNIQUE_INDEX_PKEY(pg_description_o_c_o_index, 2675, DescriptionObjIndexId, pg_description, btree(objoid oid_ops, classoid oid_ops, objsubid int4_ops));
  69
  70 /* We do not use BKI_LOOKUP here because it causes problems for genbki.pl */
  71 DECLARE_FOREIGN_KEY((classoid), pg_class, (oid));
  72
  73 #endif                                                  /* PG_DESCRIPTION_H */