On Tue, Oct 19, 2021 at 2:25 PM Dilip Kumar <dilipbal...@gmail.com> wrote:
>
> On Tue, Oct 12, 2021 at 11:30 AM Dilip Kumar <dilipbal...@gmail.com> wrote:
> >
> > On Tue, Oct 12, 2021 at 10:35 AM Kyotaro Horiguchi
> > <horikyota....@gmail.com> wrote:
> > >
> > > At Tue, 12 Oct 2021 13:59:59 +0900 (JST), Kyotaro Horiguchi
> > > <horikyota....@gmail.com> wrote in
> > > > So I came up with the attached version.
> > >
> > > Sorry, it was losing a piece of change.
> >
> > Yeah, at a high level this is on the idea I have in mind, I will do a
> > detailed review in a day or two. Thanks for working on this.
>
> While doing the detailed review, I think there are a couple of
> problems with the patch, the main problem of storing all the xid in
> the snap->subxip is that once we mark the snapshot overflown then the
> XidInMVCCSnapshot, will not search the subxip array, instead it will
> fetch the topXid and search in the snap->xip array.
I missed that you are marking the snapshot as takenDuringRecovery so
your fix looks fine.
Another issue is
> that the total xids could be GetMaxSnapshotSubxidCount()
> +GetMaxSnapshotXidCount().
>
I have fixed this, the updated patch is attached.
--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com
From b6ca7a05b05a9244bf400d14b75dfcd1f99c76cd Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyota....@gmail.com>
Date: Tue, 12 Oct 2021 13:53:27 +0900
Subject: [PATCH v3] Allow overflowed snapshot when creating logical
replication slot
Snapshot can hold top XIDs up to the number of server processes but
SnapBuildInitialSnapshot tries to store all top-level and sub XIDs to
there and fails for certain circumstances. Instead, create a
"takenDuringRecovery" snapshot instead, which stores all XIDs in
subxip array. Addition to that, allow to create an overflowed
snapshot by adding to reorder buffer a function to tell whether an XID
is a top-level or not.
---
src/backend/replication/logical/reorderbuffer.c | 20 +++++++++
src/backend/replication/logical/snapbuild.c | 57 +++++++++++++++++++------
src/include/replication/reorderbuffer.h | 1 +
3 files changed, 66 insertions(+), 12 deletions(-)
diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index 46e6660..4e452cc 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -3327,6 +3327,26 @@ ReorderBufferXidHasBaseSnapshot(ReorderBuffer *rb, TransactionId xid)
/*
+ * ReorderBufferXidIsKnownSubXact
+ * Returns true if the xid is a known subtransaction.
+ */
+bool
+ReorderBufferXidIsKnownSubXact(ReorderBuffer *rb, TransactionId xid)
+{
+ ReorderBufferTXN *txn;
+
+ txn = ReorderBufferTXNByXid(rb, xid, false,
+ NULL, InvalidXLogRecPtr, false);
+
+ /* a known subtxn? */
+ if (txn && rbtxn_is_known_subxact(txn))
+ return true;
+
+ return false;
+}
+
+
+/*
* ---------------------------------------
* Disk serialization support
* ---------------------------------------
diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index dbdc172..9fd28d4 100644
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -531,8 +531,9 @@ SnapBuildInitialSnapshot(SnapBuild *builder)
{
Snapshot snap;
TransactionId xid;
- TransactionId *newxip;
- int newxcnt = 0;
+ TransactionId *newsubxip;
+ int maxxidcnt;
+ bool overflowed = false;
Assert(!FirstSnapshotSet);
Assert(XactIsoLevel == XACT_REPEATABLE_READ);
@@ -568,9 +569,13 @@ SnapBuildInitialSnapshot(SnapBuild *builder)
MyProc->xmin = snap->xmin;
- /* allocate in transaction context */
- newxip = (TransactionId *)
- palloc(sizeof(TransactionId) * GetMaxSnapshotXidCount());
+ /*
+ * Allocate in transaction context. We use only subxip to store xids. See
+ * GetSnapshotData for details.
+ */
+ newsubxip = (TransactionId *) palloc(sizeof(TransactionId) *
+ (GetMaxSnapshotXidCount() +
+ GetMaxSnapshotSubxidCount()));
/*
* snapbuild.c builds transactions in an "inverted" manner, which means it
@@ -578,6 +583,9 @@ SnapBuildInitialSnapshot(SnapBuild *builder)
* classical snapshot by marking all non-committed transactions as
* in-progress. This can be expensive.
*/
+retry:
+ newsubxcnt = 0;
+
for (xid = snap->xmin; NormalTransactionIdPrecedes(xid, snap->xmax);)
{
void *test;
@@ -591,12 +599,29 @@ SnapBuildInitialSnapshot(SnapBuild *builder)
if (test == NULL)
{
- if (newxcnt >= GetMaxSnapshotXidCount())
- ereport(ERROR,
- (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
- errmsg("initial slot snapshot too large")));
+ bool add = true;
- newxip[newxcnt++] = xid;
+ /* exlude subxids when subxip is overflowed */
+ if (overflowed &&
+ ReorderBufferXidIsKnownSubXact(builder->reorder, xid))
+ add = false;
+
+ if (add)
+ {
+ if (newsubxcnt >= GetMaxSnapshotSubxidCount())
+ {
+ if (overflowed)
+ ereport(ERROR,
+ (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+ errmsg("initial slot snapshot too large")));
+
+ /* retry excluding subxids */
+ overflowed = true;
+ goto retry;
+ }
+
+ newsubxip[newsubxcnt++] = xid;
+ }
}
TransactionIdAdvance(xid);
@@ -604,8 +629,16 @@ SnapBuildInitialSnapshot(SnapBuild *builder)
/* adjust remaining snapshot fields as needed */
snap->snapshot_type = SNAPSHOT_MVCC;
- snap->xcnt = newxcnt;
- snap->xip = newxip;
+ snap->xcnt = 0;
+ snap->subxcnt = newsubxcnt;
+ snap->subxip = newsubxip;
+ snap->suboverflowed = overflowed;
+
+ /*
+ * Although this snapshot is taken actually not during recovery, all XIDs
+ * are stored in subxip even if it is not overflowed.
+ */
+ snap->takenDuringRecovery = true;
return snap;
}
diff --git a/src/include/replication/reorderbuffer.h b/src/include/replication/reorderbuffer.h
index 5b40ff7..e5fa105 100644
--- a/src/include/replication/reorderbuffer.h
+++ b/src/include/replication/reorderbuffer.h
@@ -669,6 +669,7 @@ void ReorderBufferXidSetCatalogChanges(ReorderBuffer *, TransactionId xid, XLog
bool ReorderBufferXidHasCatalogChanges(ReorderBuffer *, TransactionId xid);
bool ReorderBufferXidHasBaseSnapshot(ReorderBuffer *, TransactionId xid);
+bool ReorderBufferXidIsKnownSubXact(ReorderBuffer *rb, TransactionId xid);
bool ReorderBufferRememberPrepareInfo(ReorderBuffer *rb, TransactionId xid,
XLogRecPtr prepare_lsn, XLogRecPtr end_lsn,
TimestampTz prepare_time,
--
1.8.3.1
