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Commit3df51ca

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Fix CLUSTER progress reporting of number of blocks scanned.
Previously pg_stat_progress_cluster view reported the current blocknumber in heap scan as the number of heap blocks scanned (i.e.,heap_blks_scanned). This reported number could be incorrect whensynchronize_seqscans is enabled, because it allowed the heap scan tostart at block in middle. This could result in wraparounds in theheap_blks_scanned column when the heap scan wrapped around.This commit fixes the bug by calculating the number of blocks fromthe block that the heap scan starts at to the current block in scan,and reporting that number in the heap_blks_scanned column.Also, in pg_stat_progress_cluster view, previously heap_blks_scannedcould not reach heap_blks_total at the end of heap scan phaseif the last pages scanned were empty. This commit fixes the bug bymanually updating heap_blks_scanned to the same value asheap_blks_total when the heap scan phase finishes.Back-patch to v12 where pg_stat_progress_cluster view was introduced.Reported-by: Matthias van de MeentAuthor: Matthias van de MeentReviewed-by: Fujii MasaoDiscussion:https://postgr.es/m/CAEze2WjCBWSGkVfYag001Rc4+-nNLDpWM7QbyD6yPvuhKs-gYQ@mail.gmail.com
1 parentef848f4 commit3df51ca

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‎src/backend/access/heap/heapam_handler.c

Lines changed: 27 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -698,6 +698,7 @@ heapam_relation_copy_for_cluster(Relation OldHeap, Relation NewHeap,
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Datum*values;
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bool*isnull;
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BufferHeapTupleTableSlot*hslot;
701+
BlockNumberprev_cblock=InvalidBlockNumber;
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/* Remember if it's a system catalog */
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is_system_catalog=IsSystemRelation(OldHeap);
@@ -793,14 +794,38 @@ heapam_relation_copy_for_cluster(Relation OldHeap, Relation NewHeap,
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else
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{
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if (!table_scan_getnextslot(tableScan,ForwardScanDirection,slot))
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{
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/*
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* If the last pages of the scan were empty, we would go to
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* the next phase while heap_blks_scanned != heap_blks_total.
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* Instead, to ensure that heap_blks_scanned is equivalent to
802+
* total_heap_blks after the table scan phase, this parameter
803+
* is manually updated to the correct value when the table
804+
* scan finishes.
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*/
806+
pgstat_progress_update_param(PROGRESS_CLUSTER_HEAP_BLKS_SCANNED,
807+
heapScan->rs_nblocks);
796808
break;
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}
797810

798811
/*
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* In scan-and-sort mode and also VACUUM FULL, set heap blocks
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* scanned
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*
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* Note that heapScan may start at an offset and wrap around, i.e.
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* rs_startblock may be >0, and rs_cblock may end with a number
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* below rs_startblock. To prevent showing this wraparound to the
818+
* user, we offset rs_cblock by rs_startblock (modulo rs_nblocks).
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*/
802-
pgstat_progress_update_param(PROGRESS_CLUSTER_HEAP_BLKS_SCANNED,
803-
heapScan->rs_cblock+1);
820+
if (prev_cblock!=heapScan->rs_cblock)
821+
{
822+
pgstat_progress_update_param(PROGRESS_CLUSTER_HEAP_BLKS_SCANNED,
823+
(heapScan->rs_cblock+
824+
heapScan->rs_nblocks-
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heapScan->rs_startblock
826+
) %heapScan->rs_nblocks+1);
827+
prev_cblock=heapScan->rs_cblock;
828+
}
804829
}
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806831
tuple=ExecFetchSlotHeapTuple(slot, false,NULL);

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