Re: Fix obsolete comment in GetSnapshotData

On 31 March 2017 at 21:59, Robert Haas <robertmhaas@gmail.com> wrote:
> On Wed, Mar 29, 2017 at 12:00 AM, Craig Ringer <craig@2ndquadrant.com> wrote:
>> There's an outdated reference to GetOldestXmin(true, true) in
>> GetSnapshotData. It hasn't had that call signature for a long while
>> now. Update the comment to reflect the current signature.
>>
>> diff --git a/src/backend/storage/ipc/procarray.c
>> b/src/backend/storage/ipc/procarray.c
>> index f32881b..4bf0243 100644
>> --- a/src/backend/storage/ipc/procarray.c
>> +++ b/src/backend/storage/ipc/procarray.c
>> @@ -1556,7 +1556,8 @@ GetMaxSnapshotSubxidCount(void)
>>   *          older than this are known not running any more.
>>   *      RecentGlobalXmin: the global xmin (oldest TransactionXmin across all
>>   *          running transactions, except those running LAZY VACUUM).  This is
>> - *          the same computation done by GetOldestXmin(true, true).
>> + *          the same computation done by
>> + *          GetOldestXmin(NULL, PROCARRAY_FLAGS_DEFAULT|PROCARRAY_FLAGS_VACUUM)
>>   *      RecentGlobalDataXmin: the global xmin for non-catalog tables
>>   *          >= RecentGlobalXmin
>>   *
>
> PROCARRAY_FLAGS_VACUUM is defined as a bitwise or with
> PROCARRAY_FLAGS_DEFAULT.  So or-ing it back with that same value does
> not seem quite right.

You're right, I muddled it with PROCARRAY_VACUUM_FLAG.

PROCARRAY_FLAGS_VACUUM is sufficient.



diff --git a/src/backend/storage/ipc/procarray.c
b/src/backend/storage/ipc/procarray.c
index f32881b..4bf0243 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -1556,7 +1556,8 @@ GetMaxSnapshotSubxidCount(void) *          older than this are known not running any more. *
RecentGlobalXmin:the global xmin (oldest TransactionXmin across all *          running transactions, except those
runningLAZY VACUUM).  This is
 
- *          the same computation done by GetOldestXmin(true, true).
+ *          the same computation done by
+ *          GetOldestXmin(NULL, PROCARRAY_FLAGS_VACUUM) *      RecentGlobalDataXmin: the global xmin for non-catalog
tables*          >= RecentGlobalXmin *
 


-- Craig Ringer                   http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services