On Fri, Jul 1, 2016 at 11:12 AM, Amit Kapila <amit.kapil...@gmail.com> wrote: > On Thu, Jun 30, 2016 at 8:10 PM, Masahiko Sawada <sawada.m...@gmail.com> > wrote: >> On Thu, Jun 30, 2016 at 3:12 PM, Amit Kapila <amit.kapil...@gmail.com> wrote: >>> On Thu, Jun 30, 2016 at 9:13 AM, Andres Freund <and...@anarazel.de> wrote: >>>> On 2016-06-30 08:59:16 +0530, Amit Kapila wrote: >>>>> On Wed, Jun 29, 2016 at 10:30 PM, Andres Freund <and...@anarazel.de> >>>>> wrote: >>>>> > On 2016-06-29 19:04:31 +0530, Amit Kapila wrote: >>>>> >> There is nothing in this record which recorded the information about >>>>> >> visibility clear flag. >>>>> > >>>>> > I think we can actually defer the clearing to the lock release? >>>>> >>>>> How about the case if after we release the lock on page, the heap page >>>>> gets flushed, but not vm and then server crashes? >>>> >>>> In the released branches there's no need to clear all visible at that >>>> point. Note how heap_lock_tuple doesn't clear it at all. So we should be >>>> fine there, and that's the part where reusing an existing record is >>>> important (for compatibility). >>>> >>> >>> For back branches, I agree that heap_lock_tuple is sufficient, >> >> Even if we use heap_lock_tuple, If server crashed after flushed heap >> but not vm, after crash recovery the heap is still marked all-visible >> on vm. > > So, in this case both vm and page will be marked as all_visible. > >> This case could be happen even on released branched, and could make >> IndexOnlyScan returns wrong result? >> > > Why do you think IndexOnlyScan will return wrong result? If the > server crash in the way as you described, the transaction that has > made modifications will anyway be considered aborted, so the result of > IndexOnlyScan should not be wrong. >
Ah, you're right, I misunderstood. Attached updated patch incorporating your comments. I've changed it so that heap_xlog_lock clears vm flags if page is marked all frozen. Regards, -- Masahiko Sawada
emit_wal_already_marked_true_case_v2.patch
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