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fix: ExplainNode guard against NULL planstate on QE #1865

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fix: ExplainNode guard against NULL planstate on QE #1865

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e2e433b
Fix segfault in ExplainNode() on a QE
roaldm153 Jul 27, 2026
d3b5e84
fix: comments grammar
roaldm153 Jul 27, 2026
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16 changes: 13 additions & 3 deletions src/backend/commands/explain.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1540,7 +1540,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
const char *relationship, const char *plan_name,
ExplainState *es)
{
Plan *plan = planstate->plan;
Plan *plan;
PlanState *parentplanstate;
ExecSlice *save_currentSlice = es->currentSlice; /* save */
const char *pname; /* node type name for text output */
Expand All @@ -1557,6 +1557,13 @@ ExplainNode(PlanState *planstate, List *ancestors,
int motion_recv;
int motion_snd;
ExecSlice *parentSlice = NULL;
/*
* Guard against the case where a subtree on the QE lives in another slice
* and is not instantiated in this slice.

@Alena0704 Alena0704 Jul 27, 2026

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The comment doesn't say where the decision not to instantiate the subtree is made, so a reader has no starting point. I think you should add a pointer to ExecInitMotion here:

/*
 * Guard against the case where a subtree on the QE lives in another slice
 * and is not instantiated in this slice (see ExecInitMotion).
 */

*/
if (planstate == NULL)
return;
plan = planstate->plan;

/* Remember who called us. */
parentplanstate = es->parentPlanState;
Expand Down Expand Up @@ -2945,8 +2952,11 @@ ExplainNode(PlanState *planstate, List *ancestors,
/* lefttree */
if (outerPlan(plan) && !skip_outer)
{
ExplainNode(outerPlanState(planstate), ancestors,
"Outer", NULL, es);
if (outerPlanState(planstate))
{
ExplainNode(outerPlanState(planstate), ancestors,
"Outer", NULL, es);
}
}
else if (skip_outer)
{
Expand Down
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