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Commit bb437f9

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david-rowleydavid-rowley
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Add TID Range Scans to support efficient scanning ranges of TIDs
This adds a new executor node named TID Range Scan. The query planner will generate paths for TID Range scans when quals are discovered on base relations which search for ranges on the table's ctid column. These ranges may be open at either end. For example, WHERE ctid >= '(10,0)'; will return all tuples on page 10 and over. To support this, two new optional callback functions have been added to table AM. scan_set_tidrange is used to set the scan range to just the given range of TIDs. scan_getnextslot_tidrange fetches the next tuple in the given range. For AMs were scanning ranges of TIDs would not make sense, these functions can be set to NULL in the TableAmRoutine. The query planner won't generate TID Range Scan Paths in that case. Author: Edmund Horner, David Rowley Reviewed-by: David Rowley, Tomas Vondra, Tom Lane, Andres Freund, Zhihong Yu Discussion: https://postgr.es/m/CAMyN-kB-nFTkF=VA_JPwFNo08S0d-Yk0F741S2B7LDmYAi8eyA@mail.gmail.com
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‎src/backend/access/heap/heapam.c

Copy file name to clipboardExpand all lines: src/backend/access/heap/heapam.c
+147Lines changed: 147 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1391,6 +1391,153 @@ heap_getnextslot(TableScanDesc sscan, ScanDirection direction, TupleTableSlot *s
13911391
return true;
13921392
}
13931393

1394+
void
1395+
heap_set_tidrange(TableScanDesc sscan, ItemPointer mintid,
1396+
ItemPointer maxtid)
1397+
{
1398+
HeapScanDesc scan = (HeapScanDesc) sscan;
1399+
BlockNumber startBlk;
1400+
BlockNumber numBlks;
1401+
ItemPointerData highestItem;
1402+
ItemPointerData lowestItem;
1403+
1404+
/*
1405+
* For relations without any pages, we can simply leave the TID range
1406+
* unset. There will be no tuples to scan, therefore no tuples outside
1407+
* the given TID range.
1408+
*/
1409+
if (scan->rs_nblocks == 0)
1410+
return;
1411+
1412+
/*
1413+
* Set up some ItemPointers which point to the first and last possible
1414+
* tuples in the heap.
1415+
*/
1416+
ItemPointerSet(&highestItem, scan->rs_nblocks - 1, MaxOffsetNumber);
1417+
ItemPointerSet(&lowestItem, 0, FirstOffsetNumber);
1418+
1419+
/*
1420+
* If the given maximum TID is below the highest possible TID in the
1421+
* relation, then restrict the range to that, otherwise we scan to the end
1422+
* of the relation.
1423+
*/
1424+
if (ItemPointerCompare(maxtid, &highestItem) < 0)
1425+
ItemPointerCopy(maxtid, &highestItem);
1426+
1427+
/*
1428+
* If the given minimum TID is above the lowest possible TID in the
1429+
* relation, then restrict the range to only scan for TIDs above that.
1430+
*/
1431+
if (ItemPointerCompare(mintid, &lowestItem) > 0)
1432+
ItemPointerCopy(mintid, &lowestItem);
1433+
1434+
/*
1435+
* Check for an empty range and protect from would be negative results
1436+
* from the numBlks calculation below.
1437+
*/
1438+
if (ItemPointerCompare(&highestItem, &lowestItem) < 0)
1439+
{
1440+
/* Set an empty range of blocks to scan */
1441+
heap_setscanlimits(sscan, 0, 0);
1442+
return;
1443+
}
1444+
1445+
/*
1446+
* Calculate the first block and the number of blocks we must scan. We
1447+
* could be more aggressive here and perform some more validation to try
1448+
* and further narrow the scope of blocks to scan by checking if the
1449+
* lowerItem has an offset above MaxOffsetNumber. In this case, we could
1450+
* advance startBlk by one. Likewise, if highestItem has an offset of 0
1451+
* we could scan one fewer blocks. However, such an optimization does not
1452+
* seem worth troubling over, currently.
1453+
*/
1454+
startBlk = ItemPointerGetBlockNumberNoCheck(&lowestItem);
1455+
1456+
numBlks = ItemPointerGetBlockNumberNoCheck(&highestItem) -
1457+
ItemPointerGetBlockNumberNoCheck(&lowestItem) + 1;
1458+
1459+
/* Set the start block and number of blocks to scan */
1460+
heap_setscanlimits(sscan, startBlk, numBlks);
1461+
1462+
/* Finally, set the TID range in sscan */
1463+
ItemPointerCopy(&lowestItem, &sscan->rs_mintid);
1464+
ItemPointerCopy(&highestItem, &sscan->rs_maxtid);
1465+
}
1466+
1467+
bool
1468+
heap_getnextslot_tidrange(TableScanDesc sscan, ScanDirection direction,
1469+
TupleTableSlot *slot)
1470+
{
1471+
HeapScanDesc scan = (HeapScanDesc) sscan;
1472+
ItemPointer mintid = &sscan->rs_mintid;
1473+
ItemPointer maxtid = &sscan->rs_maxtid;
1474+
1475+
/* Note: no locking manipulations needed */
1476+
for (;;)
1477+
{
1478+
if (sscan->rs_flags & SO_ALLOW_PAGEMODE)
1479+
heapgettup_pagemode(scan, direction, sscan->rs_nkeys, sscan->rs_key);
1480+
else
1481+
heapgettup(scan, direction, sscan->rs_nkeys, sscan->rs_key);
1482+
1483+
if (scan->rs_ctup.t_data == NULL)
1484+
{
1485+
ExecClearTuple(slot);
1486+
return false;
1487+
}
1488+
1489+
/*
1490+
* heap_set_tidrange will have used heap_setscanlimits to limit the
1491+
* range of pages we scan to only ones that can contain the TID range
1492+
* we're scanning for. Here we must filter out any tuples from these
1493+
* pages that are outwith that range.
1494+
*/
1495+
if (ItemPointerCompare(&scan->rs_ctup.t_self, mintid) < 0)
1496+
{
1497+
ExecClearTuple(slot);
1498+
1499+
/*
1500+
* When scanning backwards, the TIDs will be in descending order.
1501+
* Future tuples in this direction will be lower still, so we can
1502+
* just return false to indicate there will be no more tuples.
1503+
*/
1504+
if (ScanDirectionIsBackward(direction))
1505+
return false;
1506+
1507+
continue;
1508+
}
1509+
1510+
/*
1511+
* Likewise for the final page, we must filter out TIDs greater than
1512+
* maxtid.
1513+
*/
1514+
if (ItemPointerCompare(&scan->rs_ctup.t_self, maxtid) > 0)
1515+
{
1516+
ExecClearTuple(slot);
1517+
1518+
/*
1519+
* When scanning forward, the TIDs will be in ascending order.
1520+
* Future tuples in this direction will be higher still, so we can
1521+
* just return false to indicate there will be no more tuples.
1522+
*/
1523+
if (ScanDirectionIsForward(direction))
1524+
return false;
1525+
continue;
1526+
}
1527+
1528+
break;
1529+
}
1530+
1531+
/*
1532+
* if we get here it means we have a new current scan tuple, so point to
1533+
* the proper return buffer and return the tuple.
1534+
*/
1535+
pgstat_count_heap_getnext(scan->rs_base.rs_rd);
1536+
1537+
ExecStoreBufferHeapTuple(&scan->rs_ctup, slot, scan->rs_cbuf);
1538+
return true;
1539+
}
1540+
13941541
/*
13951542
* heap_fetch - retrieve tuple with given tid
13961543
*

‎src/backend/access/heap/heapam_handler.c

Copy file name to clipboardExpand all lines: src/backend/access/heap/heapam_handler.c
+3Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2542,6 +2542,9 @@ static const TableAmRoutine heapam_methods = {
25422542
.scan_rescan = heap_rescan,
25432543
.scan_getnextslot = heap_getnextslot,
25442544

2545+
.scan_set_tidrange = heap_set_tidrange,
2546+
.scan_getnextslot_tidrange = heap_getnextslot_tidrange,
2547+
25452548
.parallelscan_estimate = table_block_parallelscan_estimate,
25462549
.parallelscan_initialize = table_block_parallelscan_initialize,
25472550
.parallelscan_reinitialize = table_block_parallelscan_reinitialize,

‎src/backend/commands/explain.c

Copy file name to clipboardExpand all lines: src/backend/commands/explain.c
+23Lines changed: 23 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1057,6 +1057,7 @@ ExplainPreScanNode(PlanState *planstate, Bitmapset **rels_used)
10571057
case T_IndexOnlyScan:
10581058
case T_BitmapHeapScan:
10591059
case T_TidScan:
1060+
case T_TidRangeScan:
10601061
case T_SubqueryScan:
10611062
case T_FunctionScan:
10621063
case T_TableFuncScan:
@@ -1223,6 +1224,9 @@ ExplainNode(PlanState *planstate, List *ancestors,
12231224
case T_TidScan:
12241225
pname = sname = "Tid Scan";
12251226
break;
1227+
case T_TidRangeScan:
1228+
pname = sname = "Tid Range Scan";
1229+
break;
12261230
case T_SubqueryScan:
12271231
pname = sname = "Subquery Scan";
12281232
break;
@@ -1417,6 +1421,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
14171421
case T_SampleScan:
14181422
case T_BitmapHeapScan:
14191423
case T_TidScan:
1424+
case T_TidRangeScan:
14201425
case T_SubqueryScan:
14211426
case T_FunctionScan:
14221427
case T_TableFuncScan:
@@ -1871,6 +1876,23 @@ ExplainNode(PlanState *planstate, List *ancestors,
18711876
planstate, es);
18721877
}
18731878
break;
1879+
case T_TidRangeScan:
1880+
{
1881+
/*
1882+
* The tidrangequals list has AND semantics, so be sure to
1883+
* show it as an AND condition.
1884+
*/
1885+
List *tidquals = ((TidRangeScan *) plan)->tidrangequals;
1886+
1887+
if (list_length(tidquals) > 1)
1888+
tidquals = list_make1(make_andclause(tidquals));
1889+
show_scan_qual(tidquals, "TID Cond", planstate, ancestors, es);
1890+
show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
1891+
if (plan->qual)
1892+
show_instrumentation_count("Rows Removed by Filter", 1,
1893+
planstate, es);
1894+
}
1895+
break;
18741896
case T_ForeignScan:
18751897
show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
18761898
if (plan->qual)
@@ -3558,6 +3580,7 @@ ExplainTargetRel(Plan *plan, Index rti, ExplainState *es)
35583580
case T_IndexOnlyScan:
35593581
case T_BitmapHeapScan:
35603582
case T_TidScan:
3583+
case T_TidRangeScan:
35613584
case T_ForeignScan:
35623585
case T_CustomScan:
35633586
case T_ModifyTable:

‎src/backend/executor/Makefile

Copy file name to clipboardExpand all lines: src/backend/executor/Makefile
+1Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -67,6 +67,7 @@ OBJS = \
6767
nodeSubplan.o \
6868
nodeSubqueryscan.o \
6969
nodeTableFuncscan.o \
70+
nodeTidrangescan.o \
7071
nodeTidscan.o \
7172
nodeUnique.o \
7273
nodeValuesscan.o \

‎src/backend/executor/execAmi.c

Copy file name to clipboardExpand all lines: src/backend/executor/execAmi.c
+6Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -51,6 +51,7 @@
5151
#include "executor/nodeSubplan.h"
5252
#include "executor/nodeSubqueryscan.h"
5353
#include "executor/nodeTableFuncscan.h"
54+
#include "executor/nodeTidrangescan.h"
5455
#include "executor/nodeTidscan.h"
5556
#include "executor/nodeUnique.h"
5657
#include "executor/nodeValuesscan.h"
@@ -197,6 +198,10 @@ ExecReScan(PlanState *node)
197198
ExecReScanTidScan((TidScanState *) node);
198199
break;
199200

201+
case T_TidRangeScanState:
202+
ExecReScanTidRangeScan((TidRangeScanState *) node);
203+
break;
204+
200205
case T_SubqueryScanState:
201206
ExecReScanSubqueryScan((SubqueryScanState *) node);
202207
break;
@@ -562,6 +567,7 @@ ExecSupportsBackwardScan(Plan *node)
562567

563568
case T_SeqScan:
564569
case T_TidScan:
570+
case T_TidRangeScan:
565571
case T_FunctionScan:
566572
case T_ValuesScan:
567573
case T_CteScan:

‎src/backend/executor/execCurrent.c

Copy file name to clipboardExpand all lines: src/backend/executor/execCurrent.c
+1Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -336,6 +336,7 @@ search_plan_tree(PlanState *node, Oid table_oid,
336336
case T_IndexOnlyScanState:
337337
case T_BitmapHeapScanState:
338338
case T_TidScanState:
339+
case T_TidRangeScanState:
339340
case T_ForeignScanState:
340341
case T_CustomScanState:
341342
{

‎src/backend/executor/execProcnode.c

Copy file name to clipboardExpand all lines: src/backend/executor/execProcnode.c
+10Lines changed: 10 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -109,6 +109,7 @@
109109
#include "executor/nodeSubplan.h"
110110
#include "executor/nodeSubqueryscan.h"
111111
#include "executor/nodeTableFuncscan.h"
112+
#include "executor/nodeTidrangescan.h"
112113
#include "executor/nodeTidscan.h"
113114
#include "executor/nodeUnique.h"
114115
#include "executor/nodeValuesscan.h"
@@ -238,6 +239,11 @@ ExecInitNode(Plan *node, EState *estate, int eflags)
238239
estate, eflags);
239240
break;
240241

242+
case T_TidRangeScan:
243+
result = (PlanState *) ExecInitTidRangeScan((TidRangeScan *) node,
244+
estate, eflags);
245+
break;
246+
241247
case T_SubqueryScan:
242248
result = (PlanState *) ExecInitSubqueryScan((SubqueryScan *) node,
243249
estate, eflags);
@@ -637,6 +643,10 @@ ExecEndNode(PlanState *node)
637643
ExecEndTidScan((TidScanState *) node);
638644
break;
639645

646+
case T_TidRangeScanState:
647+
ExecEndTidRangeScan((TidRangeScanState *) node);
648+
break;
649+
640650
case T_SubqueryScanState:
641651
ExecEndSubqueryScan((SubqueryScanState *) node);
642652
break;

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