database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-08-18 12:22:09 +03:00
Code Activity

Update comments that became out-of-date with the PGXACT struct.

Browse Source 
When the "hot" members of PGPROC were split off to separate PGXACT structs,
many PGPROC fields referred to in comments were moved to PGXACT, but the
comments were neglected in the commit. Mostly this is just a search/replace
of PGPROC with PGXACT, but the way the dummy PGPROC entries are created for
prepared transactions changed more, making some of the comments totally
bogus.

Noah Misch
This commit is contained in:
Heikki Linnakangas
2012-05-14 10:22:44 +03:00
parent 64f09ca386
commit 9e4637bf89
11 changed files with 56 additions and 66 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
src/backend/utils/time/snapmgr.c
View File

@@ -19,7 +19,7 @@
* have regd_count = 1 and are counted in RegisteredSnapshots, but are not
* tracked by any resource owner.
*
* These arrangements let us reset MyProc->xmin when there are no snapshots
* These arrangements let us reset MyPgXact->xmin when there are no snapshots
* referenced by this transaction. (One possible improvement would be to be
* able to advance Xmin when the snapshot with the earliest Xmin is no longer
* referenced. That's a bit harder though, it requires more locking, and
@@ -104,7 +104,7 @@ static ActiveSnapshotElt *ActiveSnapshot = NULL;
* How many snapshots is resowner.c tracking for us?
*
* Note: for now, a simple counter is enough. However, if we ever want to be
* smarter about advancing our MyProc->xmin we will need to be more
* smarter about advancing our MyPgXact->xmin we will need to be more
* sophisticated about this, perhaps keeping our own list of snapshots.
*/
static int RegisteredSnapshots = 0;
@@ -266,7 +266,7 @@ SetTransactionSnapshot(Snapshot sourcesnap, TransactionId sourcexid)
/* NB: curcid should NOT be copied, it's a local matter */
/*
* Now we have to fix what GetSnapshotData did with MyProc->xmin and
* Now we have to fix what GetSnapshotData did with MyPgXact->xmin and
* TransactionXmin. There is a race condition: to make sure we are not
* causing the global xmin to go backwards, we have to test that the
* source transaction is still running, and that has to be done atomically.
@@ -569,7 +569,7 @@ UnregisterSnapshotFromOwner(Snapshot snapshot, ResourceOwner owner)
/*
* SnapshotResetXmin
*
* If there are no more snapshots, we can reset our PGPROC->xmin to InvalidXid.
* If there are no more snapshots, we can reset our PGXACT->xmin to InvalidXid.
* Note we can do this without locking because we assume that storing an Xid
* is atomic.
*/

4
src/backend/utils/time/tqual.c
View File

@@ -10,12 +10,12 @@
* the passed-in buffer. The caller must hold not only a pin, but at least
* shared buffer content lock on the buffer containing the tuple.
*
* NOTE: must check TransactionIdIsInProgress (which looks in PGPROC array)
* NOTE: must check TransactionIdIsInProgress (which looks in PGXACT array)
* before TransactionIdDidCommit/TransactionIdDidAbort (which look in
* pg_clog). Otherwise we have a race condition: we might decide that a
* just-committed transaction crashed, because none of the tests succeed.
* xact.c is careful to record commit/abort in pg_clog before it unsets
* MyProc->xid in PGPROC array. That fixes that problem, but it also
* MyPgXact->xid in PGXACT array. That fixes that problem, but it also
* means there is a window where TransactionIdIsInProgress and
* TransactionIdDidCommit will both return true. If we check only
* TransactionIdDidCommit, we could consider a tuple committed when a