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Commitbcc6c4c

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Fix performance issue in EXPLAIN (ANALYZE, TIMING OFF).
Commitaf7914c, which added the TIMINGoption to EXPLAIN, had an oversight: if the TIMING option is disabledthen control in InstrStartNode() goes through an elog(DEBUG2) call, whichtypically does nothing but takes a noticeable amount of time to do it.Tweak the logic to avoid that.In HEAD, also change the elog(DEBUG2)'s in instrument.c to elog(ERROR).It's not very clear why they weren't like that to begin with, but thisepisode shows that not complaining more vociferously about misuse islikely to do little except allow bugs to remain hidden.While at it, adjust some code that was making possibly-dangerousassumptions about flag bits being in the rightmost byte of theinstrument_options word.Problem reported by Pavel Stehule (via Tomas Vondra).
1 parent9221f9d commitbcc6c4c

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+11
-13
lines changed

1 file changed

+11
-13
lines changed

‎src/backend/executor/instrument.c

Lines changed: 11 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -33,9 +33,9 @@ InstrAlloc(int n, int instrument_options)
3333
instr=palloc0(n*sizeof(Instrumentation));
3434
if (instrument_options& (INSTRUMENT_BUFFERS |INSTRUMENT_TIMER))
3535
{
36+
boolneed_buffers= (instrument_options&INSTRUMENT_BUFFERS)!=0;
37+
boolneed_timer= (instrument_options&INSTRUMENT_TIMER)!=0;
3638
inti;
37-
boolneed_buffers=instrument_options&INSTRUMENT_BUFFERS;
38-
boolneed_timer=instrument_options&INSTRUMENT_TIMER;
3939

4040
for (i=0;i<n;i++)
4141
{
@@ -51,10 +51,13 @@ InstrAlloc(int n, int instrument_options)
5151
void
5252
InstrStartNode(Instrumentation*instr)
5353
{
54-
if (instr->need_timer&&INSTR_TIME_IS_ZERO(instr->starttime))
55-
INSTR_TIME_SET_CURRENT(instr->starttime);
56-
else
57-
elog(DEBUG2,"InstrStartNode called twice in a row");
54+
if (instr->need_timer)
55+
{
56+
if (INSTR_TIME_IS_ZERO(instr->starttime))
57+
INSTR_TIME_SET_CURRENT(instr->starttime);
58+
else
59+
elog(ERROR,"InstrStartNode called twice in a row");
60+
}
5861

5962
/* save buffer usage totals at node entry, if needed */
6063
if (instr->need_bufusage)
@@ -73,18 +76,13 @@ InstrStopNode(Instrumentation *instr, double nTuples)
7376
/* let's update the time only if the timer was requested */
7477
if (instr->need_timer)
7578
{
76-
7779
if (INSTR_TIME_IS_ZERO(instr->starttime))
78-
{
79-
elog(DEBUG2,"InstrStopNode called without start");
80-
return;
81-
}
80+
elog(ERROR,"InstrStopNode called without start");
8281

8382
INSTR_TIME_SET_CURRENT(endtime);
8483
INSTR_TIME_ACCUM_DIFF(instr->counter,endtime,instr->starttime);
8584

8685
INSTR_TIME_SET_ZERO(instr->starttime);
87-
8886
}
8987

9088
/* Add delta of buffer usage since entry to node's totals */
@@ -111,7 +109,7 @@ InstrEndLoop(Instrumentation *instr)
111109
return;
112110

113111
if (!INSTR_TIME_IS_ZERO(instr->starttime))
114-
elog(DEBUG2,"InstrEndLoop called on running node");
112+
elog(ERROR,"InstrEndLoop called on running node");
115113

116114
/* Accumulate per-cycle statistics into totals */
117115
totaltime=INSTR_TIME_GET_DOUBLE(instr->counter);

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