Fix crashes on plans with multiple Gather (Merge) nodes.

es_query_dsa turns out to be broken by design, because it supposes
that there is only one DSA for the whole query, whereas there is
actually one per Gather (Merge) node.  For now, work around that
problem by setting and clearing the pointer around the sections of
code that might need it.  It's probably a better idea to get rid of
es_query_dsa altogether in favor of having each node keep track
individually of which DSA is relevant, but that seems like more than
we would want to back-patch.

Thomas Munro, reviewed and tested by Andreas Seltenreich, Amit
Kapila, and by me.

Discussion: http://postgr.es/m/CAEepm=1U6as=brnVvMNixEV2tpi8NuyQoTmO8Qef0-VV+=7MDA@mail.gmail.com

diff --git a/src/backend/executor/execParallel.c b/src/backend/executor/execParallel.c
index d57cdbd4e153dc2e5211fd3a9ff3e95dbbcf6d01..6b6064637b88a767741cc8efd67c87a8d2608296 100644 (file)
--- a/src/backend/executor/execParallel.c
+++ b/src/backend/executor/execParallel.c
@@ -330,7 +330,7 @@ EstimateParamExecSpace(EState *estate, Bitmapset *params)
  * parameter array) and then the datum as serialized by datumSerialize().
  */
 static dsa_pointer
-SerializeParamExecParams(EState *estate, Bitmapset *params)
+SerializeParamExecParams(EState *estate, Bitmapset *params, dsa_area *area)
 {
        Size            size;
        int                     nparams;
@@ -341,8 +341,8 @@ SerializeParamExecParams(EState *estate, Bitmapset *params)
 
        /* Allocate enough space for the current parameter values. */
        size = EstimateParamExecSpace(estate, params);
-       handle = dsa_allocate(estate->es_query_dsa, size);
-       start_address = dsa_get_address(estate->es_query_dsa, handle);
+       handle = dsa_allocate(area, size);
+       start_address = dsa_get_address(area, handle);
 
        /* First write the number of parameters as a 4-byte integer. */
        nparams = bms_num_members(params);
@@ -736,12 +736,6 @@ ExecInitParallelPlan(PlanState *planstate, EState *estate,
                                                                                LWTRANCHE_PARALLEL_QUERY_DSA,
                                                                                pcxt->seg);
 
-               /*
-                * Make the area available to executor nodes running in the leader.
-                * See also ParallelQueryMain which makes it available to workers.
-                */
-               estate->es_query_dsa = pei->area;
-
                /*
                 * Serialize parameters, if any, using DSA storage.  We don't dare use
                 * the main parallel query DSM for this because we might relaunch
@@ -750,7 +744,8 @@ ExecInitParallelPlan(PlanState *planstate, EState *estate,
                 */
                if (!bms_is_empty(sendParams))
                {
-                       pei->param_exec = SerializeParamExecParams(estate, sendParams);
+                       pei->param_exec = SerializeParamExecParams(estate, sendParams,
+                                                                                                          pei->area);
                        fpes->param_exec = pei->param_exec;
                }
        }
@@ -763,7 +758,11 @@ ExecInitParallelPlan(PlanState *planstate, EState *estate,
        d.pcxt = pcxt;
        d.instrumentation = instrumentation;
        d.nnodes = 0;
+
+       /* Install our DSA area while initializing the plan. */
+       estate->es_query_dsa = pei->area;
        ExecParallelInitializeDSM(planstate, &d);
+       estate->es_query_dsa = NULL;
 
        /*
         * Make sure that the world hasn't shifted under our feet.  This could
@@ -832,19 +831,22 @@ ExecParallelReinitialize(PlanState *planstate,
        /* Free any serialized parameters from the last round. */
        if (DsaPointerIsValid(fpes->param_exec))
        {
-               dsa_free(estate->es_query_dsa, fpes->param_exec);
+               dsa_free(pei->area, fpes->param_exec);
                fpes->param_exec = InvalidDsaPointer;
        }
 
        /* Serialize current parameter values if required. */
        if (!bms_is_empty(sendParams))
        {
-               pei->param_exec = SerializeParamExecParams(estate, sendParams);
+               pei->param_exec = SerializeParamExecParams(estate, sendParams,
+                                                                                                  pei->area);
                fpes->param_exec = pei->param_exec;
        }
 
        /* Traverse plan tree and let each child node reset associated state. */
+       estate->es_query_dsa = pei->area;
        ExecParallelReInitializeDSM(planstate, pei->pcxt);
+       estate->es_query_dsa = NULL;
 }
 
 /*

diff --git a/src/backend/executor/nodeGather.c b/src/backend/executor/nodeGather.c
index a44cf8409af4ad5cd2718872a80d6aff87d91876..1697ae650d77c2a7bd2c8e9b39d452adf0c57b90 100644 (file)
--- a/src/backend/executor/nodeGather.c
+++ b/src/backend/executor/nodeGather.c
@@ -277,7 +277,13 @@ gather_getnext(GatherState *gatherstate)
 
                if (gatherstate->need_to_scan_locally)
                {
+                       EState *estate = gatherstate->ps.state;
+
+                       /* Install our DSA area while executing the plan. */
+                       estate->es_query_dsa =
+                               gatherstate->pei ? gatherstate->pei->area : NULL;
                        outerTupleSlot = ExecProcNode(outerPlan);
+                       estate->es_query_dsa = NULL;
 
                        if (!TupIsNull(outerTupleSlot))
                                return outerTupleSlot;

diff --git a/src/backend/executor/nodeGatherMerge.c b/src/backend/executor/nodeGatherMerge.c
index 4a8a59eabf1d7cbd3e4a995954d923c5adf4b553..a69777aa9510ff879a74531dcc505e39e688d999 100644 (file)
--- a/src/backend/executor/nodeGatherMerge.c
+++ b/src/backend/executor/nodeGatherMerge.c
@@ -637,8 +637,12 @@ gather_merge_readnext(GatherMergeState *gm_state, int reader, bool nowait)
                {
                        PlanState  *outerPlan = outerPlanState(gm_state);
                        TupleTableSlot *outerTupleSlot;
+                       EState *estate = gm_state->ps.state;
 
+                       /* Install our DSA area while executing the plan. */
+                       estate->es_query_dsa = gm_state->pei ? gm_state->pei->area : NULL;
                        outerTupleSlot = ExecProcNode(outerPlan);
+                       estate->es_query_dsa = NULL;
 
                        if (!TupIsNull(outerTupleSlot))
                        {