| /*------------------------------------------------------------------------- |
| * |
| * backendid.h |
| * POSTGRES backend id communication definitions |
| * |
| * |
| * Portions Copyright (c) 1996-2021, 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 ParallelLeaderBackendId; |
| |
| /* |
| * 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 */ |
