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62f34097c8
This follows in the spirit of commit dfb75e478, which created primary key and uniqueness constraints to improve the visibility of constraints imposed on the system catalogs. While our catalogs contain many foreign-key-like relationships, they don't quite follow SQL semantics, in that the convention for an omitted reference is to write zero not NULL. Plus, we have some cases in which there are arrays each of whose elements is supposed to be an FK reference; SQL has no way to model that. So we can't create actual foreign key constraints to describe the situation. Nonetheless, we can collect and use knowledge about these relationships. This patch therefore adds annotations to the catalog header files to declare foreign-key relationships. (The BKI_LOOKUP annotations cover simple cases, but we weren't previously distinguishing which such columns are allowed to contain zeroes; we also need new markings for multi-column FK references.) Then, Catalog.pm and genbki.pl are taught to collect this information into a table in a new generated header "system_fk_info.h". The only user of that at the moment is a new SQL function pg_get_catalog_foreign_keys(), which exposes the table to SQL. The oidjoins regression test is rewritten to use pg_get_catalog_foreign_keys() to find out which columns to check. Aside from removing the need for manual maintenance of that test script, this allows it to cover numerous relationships that were not checked by the old implementation based on findoidjoins. (As of this commit, 217 relationships are checked by the test, versus 181 before.) Discussion: https://postgr.es/m/3240355.1612129197@sss.pgh.pa.us
75 lines
2.8 KiB
C
75 lines
2.8 KiB
C
/*-------------------------------------------------------------------------
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*
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* pg_description.h
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* definition of the "description" system catalog (pg_description)
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*
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* Because the contents of this table are taken from the *.dat files
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* of other catalogs, there is no pg_description.dat file. The initial
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* contents are assembled by genbki.pl and loaded during initdb.
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*
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* NOTE: an object is identified by the OID of the row that primarily
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* defines the object, plus the OID of the table that that row appears in.
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* For example, a function is identified by the OID of its pg_proc row
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* plus the pg_class OID of table pg_proc. This allows unique identification
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* of objects without assuming that OIDs are unique across tables.
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*
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* Since attributes don't have OIDs of their own, we identify an attribute
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* comment by the objoid+classoid of its parent table, plus an "objsubid"
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* giving the attribute column number. "objsubid" must be zero in a comment
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* for a table itself, so that it is distinct from any column comment.
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* Currently, objsubid is unused and zero for all other kinds of objects,
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* but perhaps it might be useful someday to associate comments with
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* constituent elements of other kinds of objects (arguments of a function,
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* for example).
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*
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*
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* Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/catalog/pg_description.h
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*
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* NOTES
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* The Catalog.pm module reads this file and derives schema
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* information.
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef PG_DESCRIPTION_H
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#define PG_DESCRIPTION_H
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#include "catalog/genbki.h"
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#include "catalog/pg_description_d.h"
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/* ----------------
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* pg_description definition. cpp turns this into
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* typedef struct FormData_pg_description
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* ----------------
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*/
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CATALOG(pg_description,2609,DescriptionRelationId)
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{
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Oid objoid; /* OID of object itself */
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Oid classoid; /* OID of table containing object */
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int32 objsubid; /* column number, or 0 if not used */
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#ifdef CATALOG_VARLEN /* variable-length fields start here */
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text description BKI_FORCE_NOT_NULL; /* description of object */
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#endif
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} FormData_pg_description;
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/* ----------------
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* Form_pg_description corresponds to a pointer to a tuple with
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* the format of pg_description relation.
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* ----------------
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*/
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typedef FormData_pg_description * Form_pg_description;
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DECLARE_TOAST(pg_description, 2834, 2835);
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DECLARE_UNIQUE_INDEX_PKEY(pg_description_o_c_o_index, 2675, on pg_description using btree(objoid oid_ops, classoid oid_ops, objsubid int4_ops));
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#define DescriptionObjIndexId 2675
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/* We do not use BKI_LOOKUP here because it causes problems for genbki.pl */
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DECLARE_FOREIGN_KEY((classoid), pg_class, (oid));
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#endif /* PG_DESCRIPTION_H */
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