Update Append's idea of first_partial_plan

It turns out that after runtime partition pruning, Append's
first_partial_plan does not accurately represent partial plans to run,
if any of those got pruned.  This could limit participation of workers
in some partial subplans, if other subplans got pruned.  Fix it by
keeping an index of the first valid partial subplan in the state node,
determined at execnode Init time.

Author: David Rowley, with cosmetic changes by me.
Discussion: https://postgr.es/m/CAKJS1f8o2Yd=rOP=Et3A0FWgF+gSAOkFSU6eNhnGzTPV7nN8sQ@mail.gmail.com

diff --git a/src/backend/executor/nodeAppend.c b/src/backend/executor/nodeAppend.c
index d062cfddaccaaedb2e5b1e84ebbc5ba4724005d8..6bc3e470bf726175d16f0d949e853e3665a271f6 100644 (file)
--- a/src/backend/executor/nodeAppend.c
+++ b/src/backend/executor/nodeAppend.c
@@ -104,6 +104,7 @@ ExecInitAppend(Append *node, EState *estate, int eflags)
    PlanState **appendplanstates;
    Bitmapset  *validsubplans;
    int         nplans;
+   int         firstvalid;
    int         i,
                j;
    ListCell   *lc;
@@ -207,19 +208,30 @@ ExecInitAppend(Append *node, EState *estate, int eflags)
    /*
     * call ExecInitNode on each of the valid plans to be executed and save
     * the results into the appendplanstates array.
+    *
+    * While at it, find out the first valid partial plan.
     */
    j = i = 0;
+   firstvalid = nplans;
    foreach(lc, node->appendplans)
    {
        if (bms_is_member(i, validsubplans))
        {
            Plan       *initNode = (Plan *) lfirst(lc);
 
+           /*
+            * Record the lowest appendplans index which is a valid partial
+            * plan.
+            */
+           if (i >= node->first_partial_plan && j < firstvalid)
+               firstvalid = j;
+
            appendplanstates[j++] = ExecInitNode(initNode, estate, eflags);
        }
        i++;
    }
 
+   appendstate->as_first_partial_plan = firstvalid;
    appendstate->appendplans = appendplanstates;
    appendstate->as_nplans = nplans;
 
@@ -499,7 +511,6 @@ static bool
 choose_next_subplan_for_leader(AppendState *node)
 {
    ParallelAppendState *pstate = node->as_pstate;
-   Append     *append = (Append *) node->ps.plan;
 
    /* Backward scan is not supported by parallel-aware plans */
    Assert(ScanDirectionIsForward(node->ps.state->es_direction));
@@ -556,7 +567,7 @@ choose_next_subplan_for_leader(AppendState *node)
    }
 
    /* If non-partial, immediately mark as finished. */
-   if (node->as_whichplan < append->first_partial_plan)
+   if (node->as_whichplan < node->as_first_partial_plan)
        node->as_pstate->pa_finished[node->as_whichplan] = true;
 
    LWLockRelease(&pstate->pa_lock);
@@ -581,7 +592,6 @@ static bool
 choose_next_subplan_for_worker(AppendState *node)
 {
    ParallelAppendState *pstate = node->as_pstate;
-   Append     *append = (Append *) node->ps.plan;
 
    /* Backward scan is not supported by parallel-aware plans */
    Assert(ScanDirectionIsForward(node->ps.state->es_direction));
@@ -629,14 +639,14 @@ choose_next_subplan_for_worker(AppendState *node)
            /* Advance to the next valid plan. */
            pstate->pa_next_plan = nextplan;
        }
-       else if (node->as_whichplan > append->first_partial_plan)
+       else if (node->as_whichplan > node->as_first_partial_plan)
        {
            /*
             * Try looping back to the first valid partial plan, if there is
             * one.  If there isn't, arrange to bail out below.
             */
            nextplan = bms_next_member(node->as_valid_subplans,
-                                      append->first_partial_plan - 1);
+                                      node->as_first_partial_plan - 1);
            pstate->pa_next_plan =
                nextplan < 0 ? node->as_whichplan : nextplan;
        }
@@ -670,7 +680,7 @@ choose_next_subplan_for_worker(AppendState *node)
    if (pstate->pa_next_plan < 0)
    {
        int         nextplan = bms_next_member(node->as_valid_subplans,
-                                              append->first_partial_plan - 1);
+                                              node->as_first_partial_plan - 1);
 
        if (nextplan >= 0)
            pstate->pa_next_plan = nextplan;
@@ -686,7 +696,7 @@ choose_next_subplan_for_worker(AppendState *node)
    }
 
    /* If non-partial, immediately mark as finished. */
-   if (node->as_whichplan < append->first_partial_plan)
+   if (node->as_whichplan < node->as_first_partial_plan)
        node->as_pstate->pa_finished[node->as_whichplan] = true;
 
    LWLockRelease(&pstate->pa_lock);

diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 9fe0b790956a5ef9789c880f6c398c8115909e77..fe93e78bee86defb45b16c1a30fc289ce411c202 100644 (file)
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1087,6 +1087,8 @@ struct AppendState
    PlanState **appendplans;    /* array of PlanStates for my inputs */
    int         as_nplans;
    int         as_whichplan;
+   int         as_first_partial_plan; /* Index of 'appendplans' containing
+                                       * the first partial plan */
    ParallelAppendState *as_pstate; /* parallel coordination info */
    Size        pstate_len;     /* size of parallel coordination info */
    struct PartitionPruneState *as_prune_state;