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Commit91e9e89

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Make nodeSort.c use Datum sorts for single column sorts
Datum sorts can be significantly faster than tuple sorts, especially whenthe data type being sorted is a pass-by-value type. Something in theregion of 50-70% performance improvements appear to be possible.Just in case there's any confusion; the Datum sort is only used when thetargetlist of the Sort node contains a single column, not when there's asingle column in the sort key and multiple items in the target list.Author: Ronan DunklauReviewed-by: James Coleman, David Rowley, Ranier Vilela, Hou ZhijieTested-by: John NaylorDiscussion:https://postgr.es/m/3177670.itZtoPt7T5@aivenronan
1 parent7fa1e1e commit91e9e89

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2 files changed

+82
-25
lines changed

2 files changed

+82
-25
lines changed

‎src/backend/executor/nodeSort.c‎

Lines changed: 81 additions & 25 deletions
Original file line numberDiff line numberDiff line change
@@ -29,6 +29,16 @@
2929
*which saves the results in a temporary file or memory. After the
3030
*initial call, returns a tuple from the file with each call.
3131
*
32+
*There are two distinct ways that this sort can be performed:
33+
*
34+
*1) When the result is a single column we perform a Datum sort.
35+
*
36+
*2) When the result contains multiple columns we perform a tuple sort.
37+
*
38+
*We could do this by always performing a tuple sort, however sorting
39+
*Datums only can be significantly faster than sorting tuples,
40+
*especially when the Datums are of a pass-by-value type.
41+
*
3242
*Conditions:
3343
* -- none.
3444
*
@@ -86,31 +96,56 @@ ExecSort(PlanState *pstate)
8696
outerNode=outerPlanState(node);
8797
tupDesc=ExecGetResultType(outerNode);
8898

89-
tuplesortstate=tuplesort_begin_heap(tupDesc,
90-
plannode->numCols,
91-
plannode->sortColIdx,
92-
plannode->sortOperators,
93-
plannode->collations,
94-
plannode->nullsFirst,
95-
work_mem,
96-
NULL,
97-
node->randomAccess);
99+
if (node->datumSort)
100+
tuplesortstate=tuplesort_begin_datum(TupleDescAttr(tupDesc,0)->atttypid,
101+
plannode->sortOperators[0],
102+
plannode->collations[0],
103+
plannode->nullsFirst[0],
104+
work_mem,
105+
NULL,
106+
node->randomAccess);
107+
else
108+
tuplesortstate=tuplesort_begin_heap(tupDesc,
109+
plannode->numCols,
110+
plannode->sortColIdx,
111+
plannode->sortOperators,
112+
plannode->collations,
113+
plannode->nullsFirst,
114+
work_mem,
115+
NULL,
116+
node->randomAccess);
98117
if (node->bounded)
99118
tuplesort_set_bound(tuplesortstate,node->bound);
100119
node->tuplesortstate= (void*)tuplesortstate;
101120

102121
/*
103-
* Scan the subplan and feed all the tuples to tuplesort.
122+
* Scan the subplan and feed all the tuples to tuplesort using the
123+
* appropriate method based on the type of sort we're doing.
104124
*/
105-
106-
for (;;)
125+
if (node->datumSort)
107126
{
108-
slot=ExecProcNode(outerNode);
109-
110-
if (TupIsNull(slot))
111-
break;
112-
113-
tuplesort_puttupleslot(tuplesortstate,slot);
127+
for (;;)
128+
{
129+
slot=ExecProcNode(outerNode);
130+
131+
if (TupIsNull(slot))
132+
break;
133+
slot_getsomeattrs(slot,1);
134+
tuplesort_putdatum(tuplesortstate,
135+
slot->tts_values[0],
136+
slot->tts_isnull[0]);
137+
}
138+
}
139+
else
140+
{
141+
for (;;)
142+
{
143+
slot=ExecProcNode(outerNode);
144+
145+
if (TupIsNull(slot))
146+
break;
147+
tuplesort_puttupleslot(tuplesortstate,slot);
148+
}
114149
}
115150

116151
/*
@@ -144,15 +179,27 @@ ExecSort(PlanState *pstate)
144179
SO1_printf("ExecSort: %s\n",
145180
"retrieving tuple from tuplesort");
146181

182+
slot=node->ss.ps.ps_ResultTupleSlot;
183+
147184
/*
148-
* Get the first or next tuple from tuplesort. Returns NULL if no more
149-
* tuples. Note that we only rely on slot tuple remaining valid until the
150-
* next fetch from the tuplesort.
185+
* Fetch the next sorted item from the appropriate tuplesort function. For
186+
* datum sorts we must manage the slot ourselves and leave it clear when
187+
* tuplesort_getdatum returns false to indicate there are no more datums.
188+
* For tuple sorts, tuplesort_gettupleslot manages the slot for us and
189+
* empties the slot when it runs out of tuples.
151190
*/
152-
slot=node->ss.ps.ps_ResultTupleSlot;
153-
(void)tuplesort_gettupleslot(tuplesortstate,
154-
ScanDirectionIsForward(dir),
155-
false,slot,NULL);
191+
if (node->datumSort)
192+
{
193+
ExecClearTuple(slot);
194+
if (tuplesort_getdatum(tuplesortstate,ScanDirectionIsForward(dir),
195+
&(slot->tts_values[0]),&(slot->tts_isnull[0]),NULL))
196+
ExecStoreVirtualTuple(slot);
197+
}
198+
else
199+
(void)tuplesort_gettupleslot(tuplesortstate,
200+
ScanDirectionIsForward(dir),
201+
false,slot,NULL);
202+
156203
returnslot;
157204
}
158205

@@ -221,6 +268,15 @@ ExecInitSort(Sort *node, EState *estate, int eflags)
221268
ExecInitResultTupleSlotTL(&sortstate->ss.ps,&TTSOpsMinimalTuple);
222269
sortstate->ss.ps.ps_ProjInfo=NULL;
223270

271+
/*
272+
* We perform a Datum sort when we're sorting just a single column,
273+
* otherwise we perform a tuple sort.
274+
*/
275+
if (ExecGetResultType(outerPlanState(sortstate))->natts==1)
276+
sortstate->datumSort= true;
277+
else
278+
sortstate->datumSort= false;
279+
224280
SO1_printf("ExecInitSort: %s\n",
225281
"sort node initialized");
226282

‎src/include/nodes/execnodes.h‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2151,6 +2151,7 @@ typedef struct SortState
21512151
int64bound_Done;/* value of bound we did the sort with */
21522152
void*tuplesortstate;/* private state of tuplesort.c */
21532153
boolam_worker;/* are we a worker? */
2154+
booldatumSort;/* Datum sort instead of tuple sort? */
21542155
SharedSortInfo*shared_info;/* one entry per worker */
21552156
}SortState;
21562157

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