GetTopTransactionId函数返回main事务的XID(TopTransactionStateData中的XID)
GetCurrentTransactionId返回当前事务的XID(CurrentTransactionState中的XID)
GetTopFullTransactionId函数返回main事务的XID(TopTransactionStateData中的FullTransactionId)
GetCurrentTransactionId返回当前事务的XID(CurrentTransactionState中的FullTransactionId)
TransactionId GetTopTransactionId(void) TransactionId GetCurrentTransactionId(void) FullTransactionId GetTopFullTransactionId(void) FullTransactionId GetCurrentFullTransactionId(void)GetTopTransactionId GetSnapshotData调用者
GetSerializableTransactionSnapshotInt (src/backend/storage/lmgr/predicate.c)
GetTransactionSnapshot (src/backend/utils/time/snapmgr.c)
GetLatestSnapshot (src/backend/utils/time/snapmgr.c)
GetNonHistoricCatalogSnapshot (src/backend/utils/time/snapmgr.c)
importSnapshot --> SetTransactionSnapshot(src/backend/utils/time/snapmgr.c)
RestoreTransactionSnapshot --> SetTransactionSnapshot(src/backend/utils/time/snapmgr.c)