Add a flag to the latest snapshot from GTM when situation demands.

Catalog scans for example require the latest snapshot to see the latest changes
to the catalogs. This patch fixes the problem with catalog scans

diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index d344c68e4cd247d3280abf30614fe7ffde4a5abb..5c68490a0b696c1e04b9d251aa14201508bfab6a 100644 (file)
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -176,7 +176,7 @@ static void DisplayXidCache(void);
 
 #ifdef PGXC  /* PGXC_DATANODE */
 
-static bool GetPGXCSnapshotData(Snapshot snapshot);
+static bool GetPGXCSnapshotData(Snapshot snapshot, bool latest);
 
 typedef struct
 {
@@ -1495,7 +1495,7 @@ GetMaxSnapshotSubxidCount(void)
  * not statically allocated (see xip allocation below).
  */
 Snapshot
-GetSnapshotData(Snapshot snapshot)
+GetSnapshotData(Snapshot snapshot, bool latest)
 {
        ProcArrayStruct *arrayP = procArray;
        TransactionId xmin;
@@ -1528,7 +1528,7 @@ GetSnapshotData(Snapshot snapshot)
                 * Obtain a global snapshot for a Postgres-XC session
                 * if possible.
                 */
-               if (GetPGXCSnapshotData(snapshot))
+               if (GetPGXCSnapshotData(snapshot, latest))
                        return snapshot;
                /*
                 * We only make one exception for using local snapshot and that's the
@@ -3151,7 +3151,7 @@ UnsetGlobalSnapshotData(void)
  * Entry of snapshot obtention for Postgres-XC node
  */
 static bool
-GetPGXCSnapshotData(Snapshot snapshot)
+GetPGXCSnapshotData(Snapshot snapshot, bool latest)
 {
        /*
         * If this node is in recovery phase,
@@ -3171,7 +3171,8 @@ GetPGXCSnapshotData(Snapshot snapshot)
         */
 
        if ((IsConnFromCoord() || IsConnFromDatanode())
-                       && !IsInitProcessingMode() && !GetForceXidFromGTM())
+                       && !IsInitProcessingMode() && !GetForceXidFromGTM() &&
+                       !latest)
        {
                if (globalSnapshot.snapshot_source == SNAPSHOT_COORDINATOR)
                        GetSnapshotFromGlobalSnapshot(snapshot);

diff --git a/src/backend/storage/lmgr/predicate.c b/src/backend/storage/lmgr/predicate.c
index bad5618341e3995e538edefd17561cf6db33721e..ae34b8803bd6b87c1bc2e60d5447c440ebd38755 100644 (file)
--- a/src/backend/storage/lmgr/predicate.c
+++ b/src/backend/storage/lmgr/predicate.c
@@ -1695,7 +1695,7 @@ GetSerializableTransactionSnapshotInt(Snapshot snapshot,
 
        /* Get the snapshot, or check that it's safe to use */
        if (!TransactionIdIsValid(sourcexid))
-               snapshot = GetSnapshotData(snapshot);
+               snapshot = GetSnapshotData(snapshot, false);
        else if (!ProcArrayInstallImportedXmin(snapshot->xmin, sourcexid))
        {
                ReleasePredXact(sxact);

diff --git a/src/backend/utils/time/snapmgr.c b/src/backend/utils/time/snapmgr.c
index 3667e2f7cc60cef661e64b4ac0dce853e38b7600..084e616a615c1fbce70a603f3b1ca21bf829da12 100644 (file)
--- a/src/backend/utils/time/snapmgr.c
+++ b/src/backend/utils/time/snapmgr.c
@@ -228,7 +228,7 @@ GetTransactionSnapshot(void)
                        if (IsolationIsSerializable())
                                CurrentSnapshot = GetSerializableTransactionSnapshot(&CurrentSnapshotData);
                        else
-                               CurrentSnapshot = GetSnapshotData(&CurrentSnapshotData);
+                               CurrentSnapshot = GetSnapshotData(&CurrentSnapshotData, false);
                        /* Make a saved copy */
                        CurrentSnapshot = CopySnapshot(CurrentSnapshot);
                        FirstXactSnapshot = CurrentSnapshot;
@@ -237,7 +237,7 @@ GetTransactionSnapshot(void)
                        pairingheap_add(&RegisteredSnapshots, &FirstXactSnapshot->ph_node);
                }
                else
-                       CurrentSnapshot = GetSnapshotData(&CurrentSnapshotData);
+                       CurrentSnapshot = GetSnapshotData(&CurrentSnapshotData, false);
 
                /* Don't allow catalog snapshot to be older than xact snapshot. */
                CatalogSnapshotStale = true;
@@ -278,7 +278,7 @@ GetTransactionSnapshot(void)
        /* Don't allow catalog snapshot to be older than xact snapshot. */
        CatalogSnapshotStale = true;
 
-       CurrentSnapshot = GetSnapshotData(&CurrentSnapshotData);
+       CurrentSnapshot = GetSnapshotData(&CurrentSnapshotData, false);
 
        return CurrentSnapshot;
 }
@@ -309,7 +309,7 @@ GetLatestSnapshot(void)
        if (!FirstSnapshotSet)
                return GetTransactionSnapshot();
 
-       SecondarySnapshot = GetSnapshotData(&SecondarySnapshotData);
+       SecondarySnapshot = GetSnapshotData(&SecondarySnapshotData, true);
 
        return SecondarySnapshot;
 }
@@ -358,7 +358,7 @@ GetNonHistoricCatalogSnapshot(Oid relid)
        if (CatalogSnapshotStale)
        {
                /* Get new snapshot. */
-               CatalogSnapshot = GetSnapshotData(&CatalogSnapshotData);
+               CatalogSnapshot = GetSnapshotData(&CatalogSnapshotData, true);
 
                /*
                 * Mark new snapshost as valid.  We must do this last, in case an
@@ -426,7 +426,7 @@ SetTransactionSnapshot(Snapshot sourcesnap, TransactionId sourcexid,
         * two variables in exported snapshot files, but it seems better to have
         * snapshot importers compute reasonably up-to-date values for them.)
         */
-       CurrentSnapshot = GetSnapshotData(&CurrentSnapshotData);
+       CurrentSnapshot = GetSnapshotData(&CurrentSnapshotData, false);
 
        /*
         * Now copy appropriate fields from the source snapshot.

diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h
index 2ddad067fcc4bce18439345291ba0521f14b3df4..f3986693ff65e06de2e4bdaceca8f41f8c478b71 100644 (file)
--- a/src/include/storage/procarray.h
+++ b/src/include/storage/procarray.h
@@ -72,7 +72,7 @@ extern void ExpireOldKnownAssignedTransactionIds(TransactionId xid);
 extern int     GetMaxSnapshotXidCount(void);
 extern int     GetMaxSnapshotSubxidCount(void);
 
-extern Snapshot GetSnapshotData(Snapshot snapshot);
+extern Snapshot GetSnapshotData(Snapshot snapshot, bool latest);
 
 extern bool ProcArrayInstallImportedXmin(TransactionId xmin,
                                                         TransactionId sourcexid);