diff options
Diffstat (limited to 'src/include/access/tableam.h')
| -rw-r--r-- | src/include/access/tableam.h | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/src/include/access/tableam.h b/src/include/access/tableam.h index 1c9e802a6b1..b2ce35e2a34 100644 --- a/src/include/access/tableam.h +++ b/src/include/access/tableam.h @@ -121,7 +121,9 @@ typedef enum TU_UpdateIndexes /* * When table_tuple_update, table_tuple_delete, or table_tuple_lock fail * because the target tuple is already outdated, they fill in this struct to - * provide information to the caller about what happened. + * provide information to the caller about what happened. When those functions + * succeed, the contents of this struct should not be relied upon, except for + * `traversed`, which may be set in both success and failure cases. * * ctid is the target's ctid link: it is the same as the target's TID if the * target was deleted, or the location of the replacement tuple if the target @@ -137,6 +139,9 @@ typedef enum TU_UpdateIndexes * tuple); otherwise cmax is zero. (We make this restriction because * HeapTupleHeaderGetCmax doesn't work for tuples outdated in other * transactions.) + * + * traversed indicates if an update chain was followed in order to try to lock + * the target tuple. (This may be set in both success and failure cases.) */ typedef struct TM_FailureData { @@ -1508,7 +1513,7 @@ table_tuple_update(Relation rel, ItemPointer otid, TupleTableSlot *slot, * * Input parameters: * relation: relation containing tuple (caller must hold suitable lock) - * tid: TID of tuple to lock + * tid: TID of tuple to lock (updated if an update chain was followed) * snapshot: snapshot to use for visibility determinations * cid: current command ID (used for visibility test, and stored into * tuple's cmax if lock is successful) @@ -1533,8 +1538,10 @@ table_tuple_update(Relation rel, ItemPointer otid, TupleTableSlot *slot, * TM_WouldBlock: lock couldn't be acquired and wait_policy is skip * * In the failure cases other than TM_Invisible and TM_Deleted, the routine - * fills *tmfd with the tuple's t_ctid, t_xmax, and, if possible, t_cmax. See - * comments for struct TM_FailureData for additional info. + * fills *tmfd with the tuple's t_ctid, t_xmax, and, if possible, t_cmax. + * Additionally, in both success and failure cases, tmfd->traversed is set if + * an update chain was followed. See comments for struct TM_FailureData for + * additional info. */ static inline TM_Result table_tuple_lock(Relation rel, ItemPointer tid, Snapshot snapshot, |