postgresql/src/backend/access/table/tableam.c

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tableam: introduce table AM infrastructure. This introduces the concept of table access methods, i.e. CREATE ACCESS METHOD ... TYPE TABLE and CREATE TABLE ... USING (storage-engine). No table access functionality is delegated to table AMs as of this commit, that'll be done in following commits. Subsequent commits will incrementally abstract table access functionality to be routed through table access methods. That change is too large to be reviewed & committed at once, so it'll be done incrementally. Docs will be updated at the end, as adding them incrementally would likely make them less coherent, and definitely is a lot more work, without a lot of benefit. Table access methods are specified similar to index access methods, i.e. pg_am.amhandler returns, as INTERNAL, a pointer to a struct with callbacks. In contrast to index AMs that struct needs to live as long as a backend, typically that's achieved by just returning a pointer to a constant struct. Psql's \d+ now displays a table's access method. That can be disabled with HIDE_TABLEAM=true, which is mainly useful so regression tests can be run against different AMs. It's quite possible that this behaviour still needs to be fine tuned. For now it's not allowed to set a table AM for a partitioned table, as we've not resolved how partitions would inherit that. Disallowing allows us to introduce, if we decide that's the way forward, such a behaviour without a compatibility break. Catversion bumped, to add the heap table AM and references to it. Author: Haribabu Kommi, Andres Freund, Alvaro Herrera, Dimitri Golgov and others Discussion: https://postgr.es/m/20180703070645.wchpu5muyto5n647@alap3.anarazel.de https://postgr.es/m/20160812231527.GA690404@alvherre.pgsql https://postgr.es/m/20190107235616.6lur25ph22u5u5av@alap3.anarazel.de https://postgr.es/m/20190304234700.w5tmhducs5wxgzls@alap3.anarazel.de
2019-03-06 18:54:38 +01:00
/*----------------------------------------------------------------------
*
* tableam.c
* Table access method routines too big to be inline functions.
*
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/backend/access/table/tableam.c
*----------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/tableam.h"
/* GUC variables */
char *default_table_access_method = DEFAULT_TABLE_ACCESS_METHOD;