Handle rescan of RemoteQuery node correctly

We never had this support and we never felt the need because the use of FQS was
limited for utility statements and simple queries which can be completed
pushed down to the remote node. But in PG 10, we're seeing errors while using
cursors for queries which are FQSed. So instead of forcing regular remote
subplan on such queries, we are adding support for rescan of RemoteQuery node.

Patch by Senhu <[email protected]>

diff --git a/src/backend/executor/execAmi.c b/src/backend/executor/execAmi.c
index b802ad6956d0dc3d74797872a1e96643315b2898..83e23da368fb623e4d253c92e32bdea04d3c754d 100644 (file)
--- a/src/backend/executor/execAmi.c
+++ b/src/backend/executor/execAmi.c
@@ -232,6 +232,9 @@ ExecReScan(PlanState *node)
                case T_RemoteSubplanState:
                        ExecReScanRemoteSubplan((RemoteSubplanState *) node);
                        break;
+               case T_RemoteQueryState:
+                       ExecReScanRemoteQuery((RemoteQueryState *) node);
+                       break;
 #endif
                case T_CustomScanState:
                        ExecReScanCustomScan((CustomScanState *) node);

diff --git a/src/backend/pgxc/pool/execRemote.c b/src/backend/pgxc/pool/execRemote.c
index 14067ee0af1dd0247d8e8a46e431c22fc2610560..0286337639ddc5749c7ff7568bef8ad1e37411ba 100644 (file)
--- a/src/backend/pgxc/pool/execRemote.c
+++ b/src/backend/pgxc/pool/execRemote.c
@@ -4763,6 +4763,44 @@ ExecRemoteQuery(PlanState *pstate)
        return NULL;
 }
 
+/* ----------------------------------------------------------------
+ *             ExecReScanRemoteQuery
+ * ----------------------------------------------------------------
+ */
+void
+ExecReScanRemoteQuery(RemoteQueryState *node)
+{
+       ResponseCombiner *combiner = (ResponseCombiner *)node;
+
+       /*
+        * If we haven't queried remote nodes yet, just return. If outerplan'
+        * chgParam is not NULL then it will be re-scanned by ExecProcNode,
+        * else - no reason to re-scan it at all.
+        */
+       if (!node->query_Done)
+               return;
+
+       /*
+        * If we execute locally rescan local copy of the plan
+        */
+       if (outerPlanState(node))
+               ExecReScan(outerPlanState(node));
+
+       /*
+        * Consume any possible pending input
+        */
+       pgxc_connections_cleanup(combiner);
+
+       /* misc cleanup */
+       combiner->command_complete_count = 0;
+       combiner->description_count = 0;
+
+       /*
+        * Force query is re-bound with new parameters
+        */
+       node->query_Done = false;
+
+}
 
 /*
  * Clean up and discard any data on the data node connections that might not

diff --git a/src/include/pgxc/execRemote.h b/src/include/pgxc/execRemote.h
index 027b647c1b4d618694307c60aa558aaaa697a29a..b7c0f5b7a160990982f8751809d78268a7b0d93d 100644 (file)
--- a/src/include/pgxc/execRemote.h
+++ b/src/include/pgxc/execRemote.h
@@ -244,6 +244,7 @@ extern bool DataNodeCopyEnd(PGXCNodeHandle *handle, bool is_error);
 
 extern RemoteQueryState *ExecInitRemoteQuery(RemoteQuery *node, EState *estate, int eflags);
 extern TupleTableSlot* ExecRemoteQuery(PlanState *pstate);
+extern void ExecReScanRemoteQuery(RemoteQueryState *node);
 extern void ExecEndRemoteQuery(RemoteQueryState *step);
 extern void RemoteSubplanMakeUnique(Node *plan, int unique);
 extern RemoteSubplanState *ExecInitRemoteSubplan(RemoteSubplan *node, EState *estate, int eflags);