From d5057fc9b6a8c04204bf6ba468cacbafdea5ff9f Mon Sep 17 00:00:00 2001 From: Andrey Borodin Date: Fri, 18 Jul 2025 18:48:54 +0500 Subject: [PATCH v6 2/2] Fill next multitransaction in REDO to avoid corner case 2 --- src/backend/access/transam/multixact.c | 47 +++++++++++++++++++++++--- 1 file changed, 43 insertions(+), 4 deletions(-) diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c index 6375d0b4762..6ea0b90c6fd 100644 --- a/src/backend/access/transam/multixact.c +++ b/src/backend/access/transam/multixact.c @@ -341,7 +341,7 @@ static MemoryContext MXactContext = NULL; /* internal MultiXactId management */ static void MultiXactIdSetOldestVisible(void); static void RecordNewMultiXact(MultiXactId multi, MultiXactOffset offset, - int nmembers, MultiXactMember *members); + int nmembers, MultiXactMember *members, bool redo); static MultiXactId GetNewMultiXactId(int nmembers, MultiXactOffset *offset); /* MultiXact cache management */ @@ -843,7 +843,7 @@ MultiXactIdCreateFromMembers(int nmembers, MultiXactMember *members) (void) XLogInsert(RM_MULTIXACT_ID, XLOG_MULTIXACT_CREATE_ID); /* Now enter the information into the OFFSETs and MEMBERs logs */ - RecordNewMultiXact(multi, offset, nmembers, members); + RecordNewMultiXact(multi, offset, nmembers, members, false); /* Done with critical section */ END_CRIT_SECTION(); @@ -865,7 +865,7 @@ MultiXactIdCreateFromMembers(int nmembers, MultiXactMember *members) */ static void RecordNewMultiXact(MultiXactId multi, MultiXactOffset offset, - int nmembers, MultiXactMember *members) + int nmembers, MultiXactMember *members, bool redo) { int pageno; int prev_pageno; @@ -892,6 +892,43 @@ RecordNewMultiXact(MultiXactId multi, MultiXactOffset offset, *offptr = offset; + if (redo) // TODO: AB: I do not want to call RecoveryInProgress() here + { + MultiXactId next = multi + 1; /* we do not care about wrapraound here */ + int next_pageno = MultiXactIdToOffsetPage(next); + if (next_pageno == pageno) + { + offptr[1] = offset + nmembers; + } + else + { + int next_slotno; + MultiXactOffset *next_offptr; + int next_entryno = MultiXactIdToOffsetEntry(next); + + if (!SimpleLruDoesPhysicalPageExist(MultiXactOffsetCtl, next_pageno)) + { + int slotno; + + /* Copypasted comment from MaybeExtendOffsetSlru */ + /* + * Fortunately for us, SimpleLruWritePage is already prepared to deal + * with creating a new segment file even if the page we're writing is + * not the first in it, so this is enough. + */ + next_slotno = ZeroMultiXactOffsetPage(next_pageno, false); + SimpleLruWritePage(MultiXactOffsetCtl, next_slotno); + } + else + { + next_slotno = SimpleLruReadPage(MultiXactOffsetCtl, next_pageno, true, next); + } + next_offptr = (MultiXactOffset *) MultiXactOffsetCtl->shared->page_buffer[next_slotno]; + next_offptr[next_slotno] = offset + nmembers; + MultiXactMemberCtl->shared->page_dirty[next_slotno] = true; + } + } + MultiXactOffsetCtl->shared->page_dirty[slotno] = true; /* Exchange our lock */ @@ -1393,6 +1430,8 @@ retry: /* Corner case 2: next multixact is still being filled in */ LWLockRelease(MultiXactOffsetSLRULock); CHECK_FOR_INTERRUPTS(); + /* CHECK_FOR_INTERRUPTS above would be critical for avoiding conflicts with recovery, yet caller might hold LWLock rendegin CHECK_FOR_INTERRUPTS disfunctional */ + Assert(!RecoveryInProgress()); pg_usleep(1000L); goto retry; } @@ -3286,7 +3325,7 @@ multixact_redo(XLogReaderState *record) /* Store the data back into the SLRU files */ RecordNewMultiXact(xlrec->mid, xlrec->moff, xlrec->nmembers, - xlrec->members); + xlrec->members, true); /* Make sure nextMXact/nextOffset are beyond what this record has */ MultiXactAdvanceNextMXact(xlrec->mid + 1, -- 2.39.5 (Apple Git-154)