pg_description.h

Go to the documentation of this file.

/*-------------------------------------------------------------------------
 *
 * pg_description.h
 *    definition of the "description" system catalog (pg_description)
 *
 * Because the contents of this table are taken from the *.dat files
 * of other catalogs, there is no pg_description.dat file. The initial
 * contents are assembled by genbki.pl and loaded during initdb.
 *
 * NOTE: an object is identified by the OID of the row that primarily
 * defines the object, plus the OID of the table that that row appears in.
 * For example, a function is identified by the OID of its pg_proc row
 * plus the pg_class OID of table pg_proc.  This allows unique identification
 * of objects without assuming that OIDs are unique across tables.
 *
 * Since attributes don't have OIDs of their own, we identify an attribute
 * comment by the objoid+classoid of its parent table, plus an "objsubid"
 * giving the attribute column number.  "objsubid" must be zero in a comment
 * for a table itself, so that it is distinct from any column comment.
 * Currently, objsubid is unused and zero for all other kinds of objects,
 * but perhaps it might be useful someday to associate comments with
 * constituent elements of other kinds of objects (arguments of a function,
 * for example).
 *
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/catalog/pg_description.h
 *
 * NOTES
 *    The Catalog.pm module reads this file and derives schema
 *    information.
 *
 *-------------------------------------------------------------------------
 */
#ifndef PG_DESCRIPTION_H
#define PG_DESCRIPTION_H
 
#include "catalog/genbki.h"
#include "catalog/pg_description_d.h"   /* IWYU pragma: export */
 
/* ----------------
 *      pg_description definition.  cpp turns this into
 *      typedef struct FormData_pg_description
 * ----------------
 */
CATALOG(pg_description,2609,DescriptionRelationId)
{
    Oid         objoid;         /* OID of object itself */
    Oid         classoid;       /* OID of table containing object */
    int32       objsubid;       /* column number, or 0 if not used */
 
#ifdef CATALOG_VARLEN           /* variable-length fields start here */
    text        description BKI_FORCE_NOT_NULL; /* description of object */
#endif
} FormData_pg_description;
 
/* ----------------
 *      Form_pg_description corresponds to a pointer to a tuple with
 *      the format of pg_description relation.
 * ----------------
 */
typedef FormData_pg_description * Form_pg_description;
 
DECLARE_TOAST(pg_description, 2834, 2835);
 
DECLARE_UNIQUE_INDEX_PKEY(pg_description_o_c_o_index, 2675, DescriptionObjIndexId, pg_description, btree(objoid oid_ops, classoid oid_ops, objsubid int4_ops));
 
/* We do not use BKI_LOOKUP here because it causes problems for genbki.pl */
DECLARE_FOREIGN_KEY((classoid), pg_class, (oid));
 
#endif                          /* PG_DESCRIPTION_H */