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Diffstat (limited to 'src/include/utils/old_snapshot.h')
| -rw-r--r-- | src/include/utils/old_snapshot.h | 75 |
1 files changed, 0 insertions, 75 deletions
diff --git a/src/include/utils/old_snapshot.h b/src/include/utils/old_snapshot.h deleted file mode 100644 index f1978a28e1c..00000000000 --- a/src/include/utils/old_snapshot.h +++ /dev/null @@ -1,75 +0,0 @@ -/*------------------------------------------------------------------------- - * - * old_snapshot.h - * Data structures for 'snapshot too old' - * - * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group - * Portions Copyright (c) 1994, Regents of the University of California - * - * IDENTIFICATION - * src/include/utils/old_snapshot.h - * - *------------------------------------------------------------------------- - */ - -#ifndef OLD_SNAPSHOT_H -#define OLD_SNAPSHOT_H - -#include "datatype/timestamp.h" -#include "storage/s_lock.h" - -/* - * Structure for dealing with old_snapshot_threshold implementation. - */ -typedef struct OldSnapshotControlData -{ - /* - * Variables for old snapshot handling are shared among processes and are - * only allowed to move forward. - */ - slock_t mutex_current; /* protect current_timestamp */ - TimestampTz current_timestamp; /* latest snapshot timestamp */ - slock_t mutex_latest_xmin; /* protect latest_xmin and next_map_update */ - TransactionId latest_xmin; /* latest snapshot xmin */ - TimestampTz next_map_update; /* latest snapshot valid up to */ - slock_t mutex_threshold; /* protect threshold fields */ - TimestampTz threshold_timestamp; /* earlier snapshot is old */ - TransactionId threshold_xid; /* earlier xid may be gone */ - - /* - * Keep one xid per minute for old snapshot error handling. - * - * Use a circular buffer with a head offset, a count of entries currently - * used, and a timestamp corresponding to the xid at the head offset. A - * count_used value of zero means that there are no times stored; a - * count_used value of OLD_SNAPSHOT_TIME_MAP_ENTRIES means that the buffer - * is full and the head must be advanced to add new entries. Use - * timestamps aligned to minute boundaries, since that seems less - * surprising than aligning based on the first usage timestamp. The - * latest bucket is effectively stored within latest_xmin. The circular - * buffer is updated when we get a new xmin value that doesn't fall into - * the same interval. - * - * It is OK if the xid for a given time slot is from earlier than - * calculated by adding the number of minutes corresponding to the - * (possibly wrapped) distance from the head offset to the time of the - * head entry, since that just results in the vacuuming of old tuples - * being slightly less aggressive. It would not be OK for it to be off in - * the other direction, since it might result in vacuuming tuples that are - * still expected to be there. - * - * Use of an SLRU was considered but not chosen because it is more - * heavyweight than is needed for this, and would probably not be any less - * code to implement. - * - * Persistence is not needed. - */ - int head_offset; /* subscript of oldest tracked time */ - TimestampTz head_timestamp; /* time corresponding to head xid */ - int count_used; /* how many slots are in use */ - TransactionId xid_by_minute[FLEXIBLE_ARRAY_MEMBER]; -} OldSnapshotControlData; - -extern PGDLLIMPORT volatile OldSnapshotControlData *oldSnapshotControl; - -#endif |