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Fix possible infinite loop with Parallel Append.

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When the previously-chosen plan was non-partial, all pa_finished
flags for partial plans are now set, and pa_next_plan has not yet
been set to INVALID_SUBPLAN_INDEX, the previous code could go into
an infinite loop.

Report by Rajkumar Raghuwanshi.  Patch by Amit Khandekar and me.
Review by Kyotaro Horiguchi.

Discussion: http://postgr.es/m/CAJ3gD9cf43z78qY=U=H0HvOEN341qfRO-vLpnKPSviHeWgJQ5w@mail.gmail.com
This commit is contained in:
Robert Haas 2018-02-08 12:31:48 -05:00
parent b3a101eff0
commit 88fdc70060
1 changed files with 8 additions and 2 deletions
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10
src/backend/executor/nodeAppend.c
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@ -473,6 +473,9 @@ choose_next_subplan_for_worker(AppendState *node)
return false; return false;
} }
/* Save the plan from which we are starting the search. */
node->as_whichplan = pstate->pa_next_plan;
/* Loop until we find a subplan to execute. */ /* Loop until we find a subplan to execute. */
while (pstate->pa_finished[pstate->pa_next_plan]) while (pstate->pa_finished[pstate->pa_next_plan])
{ {
@ -481,14 +484,17 @@ choose_next_subplan_for_worker(AppendState *node)
/* Advance to next plan. */ /* Advance to next plan. */
pstate->pa_next_plan++; pstate->pa_next_plan++;
} }
else if (append->first_partial_plan < node->as_nplans) else if (node->as_whichplan > append->first_partial_plan)
{ {
/* Loop back to first partial plan. */ /* Loop back to first partial plan. */
pstate->pa_next_plan = append->first_partial_plan; pstate->pa_next_plan = append->first_partial_plan;
} }
else else
{ {
/* At last plan, no partial plans, arrange to bail out. */ /*
* At last plan, and either there are no partial plans or we've
* tried them all. Arrange to bail out.
*/
pstate->pa_next_plan = node->as_whichplan; pstate->pa_next_plan = node->as_whichplan;
} }