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Previously tables declared WITH OIDS, including a significant fraction of the catalog tables, stored the oid column not as a normal column, but as part of the tuple header. This special column was not shown by default, which was somewhat odd, as it's often (consider e.g. pg_class.oid) one of the more important parts of a row. Neither pg_dump nor COPY included the contents of the oid column by default. The fact that the oid column was not an ordinary column necessitated a significant amount of special case code to support oid columns. That already was painful for the existing, but upcoming work aiming to make table storage pluggable, would have required expanding and duplicating that "specialness" significantly. WITH OIDS has been deprecated since 2005 (commit ff02d0a05280e0). Remove it. Removing includes: - CREATE TABLE and ALTER TABLE syntax for declaring the table to be WITH OIDS has been removed (WITH (oids[ = true]) will error out) - pg_dump does not support dumping tables declared WITH OIDS and will issue a warning when dumping one (and ignore the oid column). - restoring an pg_dump archive with pg_restore will warn when restoring a table with oid contents (and ignore the oid column) - COPY will refuse to load binary dump that includes oids. - pg_upgrade will error out when encountering tables declared WITH OIDS, they have to be altered to remove the oid column first. - Functionality to access the oid of the last inserted row (like plpgsql's RESULT_OID, spi's SPI_lastoid, ...) has been removed. The syntax for declaring a table WITHOUT OIDS (or WITH (oids = false) for CREATE TABLE) is still supported. While that requires a bit of support code, it seems unnecessary to break applications / dumps that do not use oids, and are explicit about not using them. The biggest user of WITH OID columns was postgres' catalog. This commit changes all 'magic' oid columns to be columns that are normally declared and stored. To reduce unnecessary query breakage all the newly added columns are still named 'oid', even if a table's column naming scheme would indicate 'reloid' or such. This obviously requires adapting a lot code, mostly replacing oid access via HeapTupleGetOid() with access to the underlying Form_pg_*->oid column. The bootstrap process now assigns oids for all oid columns in genbki.pl that do not have an explicit value (starting at the largest oid previously used), only oids assigned later by oids will be above FirstBootstrapObjectId. As the oid column now is a normal column the special bootstrap syntax for oids has been removed. Oids are not automatically assigned during insertion anymore, all backend code explicitly assigns oids with GetNewOidWithIndex(). For the rare case that insertions into the catalog via SQL are called for the new pg_nextoid() function can be used (which only works on catalog tables). The fact that oid columns on system tables are now normal columns means that they will be included in the set of columns expanded by * (i.e. SELECT * FROM pg_class will now include the table's oid, previously it did not). It'd not technically be hard to hide oid column by default, but that'd mean confusing behavior would either have to be carried forward forever, or it'd cause breakage down the line. While it's not unlikely that further adjustments are needed, the scope/invasiveness of the patch makes it worthwhile to get merge this now. It's painful to maintain externally, too complicated to commit after the code code freeze, and a dependency of a number of other patches. Catversion bump, for obvious reasons. Author: Andres Freund, with contributions by John Naylor Discussion: https://postgr.es/m/20180930034810.ywp2c7awz7opzcfr@alap3.anarazel.de
90 lines
2.6 KiB
C
90 lines
2.6 KiB
C
/*-------------------------------------------------------------------------
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*
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* pg_cast.h
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* definition of the "type casts" system catalog (pg_cast)
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*
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* As of Postgres 8.0, pg_cast describes not only type coercion functions
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* but also length coercion functions.
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*
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* Portions Copyright (c) 1996-2018, 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_cast.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_CAST_H
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#define PG_CAST_H
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#include "catalog/genbki.h"
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#include "catalog/pg_cast_d.h"
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/* ----------------
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* pg_cast definition. cpp turns this into
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* typedef struct FormData_pg_cast
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* ----------------
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*/
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CATALOG(pg_cast,2605,CastRelationId)
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{
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Oid oid; /* oid */
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/* source datatype for cast */
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Oid castsource BKI_LOOKUP(pg_type);
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/* destination datatype for cast */
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Oid casttarget BKI_LOOKUP(pg_type);
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/* cast function; 0 = binary coercible */
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Oid castfunc BKI_LOOKUP(pg_proc);
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/* contexts in which cast can be used */
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char castcontext;
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/* cast method */
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char castmethod;
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} FormData_pg_cast;
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/* ----------------
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* Form_pg_cast corresponds to a pointer to a tuple with
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* the format of pg_cast relation.
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* ----------------
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*/
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typedef FormData_pg_cast *Form_pg_cast;
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#ifdef EXPOSE_TO_CLIENT_CODE
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/*
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* The allowable values for pg_cast.castcontext are specified by this enum.
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* Since castcontext is stored as a "char", we use ASCII codes for human
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* convenience in reading the table. Note that internally to the backend,
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* these values are converted to the CoercionContext enum (see primnodes.h),
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* which is defined to sort in a convenient order; the ASCII codes don't
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* have to sort in any special order.
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*/
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typedef enum CoercionCodes
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{
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COERCION_CODE_IMPLICIT = 'i', /* coercion in context of expression */
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COERCION_CODE_ASSIGNMENT = 'a', /* coercion in context of assignment */
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COERCION_CODE_EXPLICIT = 'e' /* explicit cast operation */
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} CoercionCodes;
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/*
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* The allowable values for pg_cast.castmethod are specified by this enum.
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* Since castmethod is stored as a "char", we use ASCII codes for human
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* convenience in reading the table.
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*/
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typedef enum CoercionMethod
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{
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COERCION_METHOD_FUNCTION = 'f', /* use a function */
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COERCION_METHOD_BINARY = 'b', /* types are binary-compatible */
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COERCION_METHOD_INOUT = 'i' /* use input/output functions */
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} CoercionMethod;
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#endif /* EXPOSE_TO_CLIENT_CODE */
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#endif /* PG_CAST_H */
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