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Fix assertion failure in getNdvBySegHeapTuple for empty partitions. #1599

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Fix assertion failure in getNdvBySegHeapTuple for empty partitions. #1599

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97f4ea5
Fix assertion failure in getNdvBySegHeapTuple for empty partitions.
zhangwenchao-123 Mar 2, 2026
080c758
Address PR review: restore Assert and convert nvalues check to runtime
Mar 10, 2026
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35 changes: 28 additions & 7 deletions src/backend/commands/analyzeutils.c
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Original file line number Diff line number Diff line change
Expand Up @@ -759,17 +759,38 @@ getNdvBySegHeapTuple(AttStatsSlot * *ndvbsSlots, HeapTuple *heaptupleStats, floa
(void) get_attstatsslot(ndvbsSlots[i], heaptupleStats[i],
STATISTIC_KIND_NDV_BY_SEGMENTS, InvalidOid, ATTSTATSSLOT_VALUES);

if ((InvalidOid != ndvbsSlots[i]->valuetype && // result is not empty
// not empty partition with invalid ndvbs
(relTuples[i] > 0 && DatumGetFloat8(ndvbsSlots[i]->values[0]) == 0)) ||
// not empty partition without ndvbs
(InvalidOid == ndvbsSlots[i]->valuetype && relTuples[i] > 0)) {
if (ndvbsSlots[i]->valuetype != FLOAT8OID)
{
/*
* NDV_BY_SEGMENTS slot not found or has unexpected type.
* Non-empty partitions must have valid NDV_BY_SEGMENTS;
* empty partitions (relTuples == 0) can be skipped.
*/
if (relTuples[i] > 0)
{
valid = false;
break;
}
free_attstatsslot(ndvbsSlots[i]);
pfree(ndvbsSlots[i]);
ndvbsSlots[i] = NULL;
continue;
}

Assert(ndvbsSlots[i]->valuetype == FLOAT8OID);

if (ndvbsSlots[i]->nvalues != 1)
{
valid = false;
break;
}

Assert(ndvbsSlots[i]->valuetype == FLOAT8OID);
Assert(ndvbsSlots[i]->nvalues == 1);
/* Non-empty partition with zero NDV is suspicious */
if (relTuples[i] > 0 && DatumGetFloat8(ndvbsSlots[i]->values[0]) == 0)
{
valid = false;
break;
}
}
return valid;
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@gfphoenix78 gfphoenix78 Mar 5, 2026

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All of the ndvbsSlots could be release if the valid becomes false. On the other side, the ndvbsSlots and its pointer array could be also freed in aggregate_leaf_partition_ndvbs no matter it's valid or not.

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@zhangwenchao-123 zhangwenchao-123 Mar 10, 2026

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Right, aggregate_leaf_partition_ndvbs will free all ndvbsSlots regardless of validity. The early cleanup here for empty partitions (setting slot to NULL after free) is just to keep the slot array consistent during iteration — it won't cause a double-free since the cleanup function checks for NULL.

}
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