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? -- With Regards, Amit Kapila. EnterpriseDB: http://www.enterprisedb.com
