greenplumn backendid 源码
greenplumn backendid 代码
文件路径：/src/include/storage/backendid.h
/*-------------------------------------------------------------------------
*
* backendid.h
* POSTGRES backend id communication definitions
*
*
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/storage/backendid.h
*
*-------------------------------------------------------------------------
*/
#ifndef BACKENDID_H
#define BACKENDID_H
/* ----------------
* -cim 8/17/90
* ----------------
*/
typedef int BackendId; /* unique currently active backend identifier */
#define InvalidBackendId (-1)
/*
* TempRelBackendId is used in GPDB in place of a real backend ID in some
* places where we deal with a temporary tables.
*
* Future enhancement: To align closer with upstream, the TempRelBackendId
* constant should be replaced with gp_session_id. In order for it to work,
* the BufferTag needs to be augmented with session ID so that we can get rid
* of two further GPDB-specific hacks: (1) BM_TEMP flag added to distinguish
* shared buffers belonging to temp relations from non-temp relations and (2)
* the additional check for collition in GetNewRelFileNode.
*
* Based on this discussion adding gp_session_id to BufferTag is considered a
* performance overhead:
* http://www.postgresql-archive.org/Keeping-temporary-tables-in-shared-buffers-td6022361.html
*
* The advantage we would get is BufferTag can never hash to the same value for
* a temp and a non-temp relation having the same RelFileNode.
*/
#define TempRelBackendId (-2)
extern PGDLLIMPORT BackendId MyBackendId; /* backend id of this backend */
/* backend id of our parallel session leader, or InvalidBackendId if none */
extern PGDLLIMPORT BackendId ParallelMasterBackendId;
/*
* The BackendId to use for our session's temp relations is normally our own,
* but parallel workers should use their leader's ID.
*
* In GPDB, we use TempRelBackendId for everything.
*/
#define BackendIdForTempRelations() TempRelBackendId
#endif /* BACKENDID_H */
相关信息
相关文章
0
赞
热门推荐
-
2、 - 优质文章
-
3、 gate.io
-
7、 golang
-
9、 openharmony
-
10、 Vue中input框自动聚焦