On Sat, Mar 7, 2020 at 3:26 PM Amit Kapila <amit.kapil...@gmail.com> wrote: > > On Sat, Mar 7, 2020 at 11:14 AM Amit Kapila <amit.kapil...@gmail.com> wrote: >> >> On Sat, Mar 7, 2020 at 9:57 AM Dilip Kumar <dilipbal...@gmail.com> wrote: >>> >>> On Fri, Mar 6, 2020 at 9:47 AM Amit Kapila <amit.kapil...@gmail.com> wrote: >>> > >>> > On Thu, Mar 5, 2020 at 1:54 PM Dilip Kumar <dilipbal...@gmail.com> wrote: >>> > > >>> > > On Thu, Mar 5, 2020 at 12:15 PM Amit Kapila <amit.kapil...@gmail.com> >>> > > wrote: >>> > > > >>> > > > >>> > > > 5. I have also tried to think of another way to check if we already >>> > > > hold lock type LOCKTAG_RELATION_EXTEND, but couldn't come up with a >>> > > > cheaper way than this. Basically, I think if we traverse the >>> > > > MyProc->myProcLocks queue, we will get this information, but that >>> > > > doesn't seem much cheaper than this. >>> > > >>> > > I think we can maintain a flag (rel_extlock_held). And, we can set >>> > > that true in LockRelationForExtension, >>> > > ConditionalLockRelationForExtension functions and we can reset it in >>> > > UnlockRelationForExtension or in the error path e.g. LockReleaseAll. >>> > > >>> > >>> > I think if we reset it in LockReleaseAll during the error path, then >>> > we need to find a way to reset it during LockReleaseCurrentOwner as >>> > that is called during Subtransaction Abort which can be tricky as we >>> > don't know if it belongs to the current owner. How about resetting in >>> > Abort(Sub)Transaction and CommitTransaction after we release locks via >>> > ResourceOwnerRelease. >>> >>> I think instead of the flag we need to keep the counter because we can >>> acquire the same relation extension lock multiple times. So >>> basically, every time we acquire the lock we can increment the counter >>> and while releasing we can decrement it. During an error path, I >>> think it is fine to set it to 0 in CommitTransaction/AbortTransaction. >>> But, I am not sure that we can set to 0 or decrement it in >>> AbortSubTransaction because we are not sure whether we have acquired >>> the lock under this subtransaction or not. >>> >>> Having said that, I think there should not be any case that we are >>> starting the sub-transaction while holding the relation extension >>> lock. >> >> >> Right, this is exactly the point. I think we can mention this in comments >> to make it clear why setting it to zero is fine during subtransaction abort. > > > Is there anything wrong with having an Assert during subtransaction start to > indicate that we don't have a relation extension lock?
Yes, I was planning to do that. -- Regards, Dilip Kumar EnterpriseDB: http://www.enterprisedb.com
