Fix thinko introduced in 2bef06d516460 et al.

The callers for GetOldestSafeDecodingTransactionId() all inverted the
argument for the argument introduced in 2bef06d516460. Luckily this
appears to be inconsequential for the moment, as we wait for
concurrent in-progress transaction when assembling a
snapshot. Additionally this could only make a difference when adding a
second logical slot, because only a pre-existing slot could cause an
issue by lowering the returned xid dangerously much.

Reported-By: Antonin Houska
Discussion: https://postgr.es/m/32704.1496993134@localhost
Backport: 9.4-, where 2bef06d516460 was backpatched to.

diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index 6a570d0e81088861404a2a9adeadcbfa67d77c5f..3745edb445d4598266d5ae9d48dcba5f6ef5d009 100644 (file)
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -327,7 +327,7 @@ CreateInitDecodingContext(char *plugin,
     */
    LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
 
-   xmin_horizon = GetOldestSafeDecodingTransactionId(need_full_snapshot);
+   xmin_horizon = GetOldestSafeDecodingTransactionId(!need_full_snapshot);
 
    slot->effective_catalog_xmin = xmin_horizon;
    slot->data.catalog_xmin = xmin_horizon;

diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index 9359fc2386db4dedab37508a228e9ea0c3bf0dcf..03ca4ba6f6118f65616e562ed52c0da382b38f38 100644 (file)
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -595,7 +595,7 @@ SnapBuildExportSnapshot(SnapBuild *builder)
        TransactionId safeXid;
 
        LWLockAcquire(ProcArrayLock, LW_SHARED);
-       safeXid = GetOldestSafeDecodingTransactionId(true);
+       safeXid = GetOldestSafeDecodingTransactionId(false);
        LWLockRelease(ProcArrayLock);
 
        Assert(TransactionIdPrecedesOrEquals(safeXid, snap->xmin));