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Add TIMING option to EXPLAIN, to allow eliminating of timing overhead.

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Sometimes it may be useful to get actual row counts out of EXPLAIN
(ANALYZE) without paying the cost of timing every node entry/exit.
With this patch, you can say EXPLAIN (ANALYZE, TIMING OFF) to get that.

Tomas Vondra, reviewed by Eric Theise, with minor doc changes by me.
This commit is contained in:
Robert Haas
2012-02-07 11:23:04 -05:00
parent 1631598ea2
commit af7914c662
6 changed files with 98 additions and 23 deletions
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45
src/backend/commands/explain.c
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@ -116,6 +116,7 @@ ExplainQuery(ExplainStmt *stmt, const char *queryString,
TupOutputState *tstate;
List *rewritten;
ListCell *lc;
bool timing_set = false;
/* Initialize ExplainState. */
ExplainInitState(&es);
@ -133,6 +134,11 @@ ExplainQuery(ExplainStmt *stmt, const char *queryString,
es.costs = defGetBoolean(opt);
else if (strcmp(opt->defname, "buffers") == 0)
es.buffers = defGetBoolean(opt);
else if (strcmp(opt->defname, "timing") == 0)
{
timing_set = true;
es.timing = defGetBoolean(opt);
}
else if (strcmp(opt->defname, "format") == 0)
{
char *p = defGetString(opt);
@ -162,6 +168,15 @@ ExplainQuery(ExplainStmt *stmt, const char *queryString,
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("EXPLAIN option BUFFERS requires ANALYZE")));
/* if the timing was not set explicitly, set default value */
es.timing = (timing_set) ? es.timing : es.analyze;
/* check that timing is used with EXPLAIN ANALYZE */
if (es.timing && !es.analyze)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("EXPLAIN option TIMING requires ANALYZE")));
/*
* Parse analysis was done already, but we still have to run the rule
@ -360,8 +375,11 @@ ExplainOnePlan(PlannedStmt *plannedstmt, ExplainState *es,
int eflags;
int instrument_option = 0;
if (es->analyze)
if (es->analyze && es->timing)
instrument_option |= INSTRUMENT_TIMER;
else if (es->analyze)
instrument_option |= INSTRUMENT_ROWS;
if (es->buffers)
instrument_option |= INSTRUMENT_BUFFERS;
@ -956,29 +974,42 @@ ExplainNode(PlanState *planstate, List *ancestors,
if (es->format == EXPLAIN_FORMAT_TEXT)
{
appendStringInfo(es->str,
" (actual time=%.3f..%.3f rows=%.0f loops=%.0f)",
startup_sec, total_sec, rows, nloops);
if (planstate->instrument->need_timer)
appendStringInfo(es->str,
" (actual time=%.3f..%.3f rows=%.0f loops=%.0f)",
startup_sec, total_sec, rows, nloops);
else
appendStringInfo(es->str,
" (actual rows=%.0f loops=%.0f)",
rows, nloops);
}
else
{
ExplainPropertyFloat("Actual Startup Time", startup_sec, 3, es);
ExplainPropertyFloat("Actual Total Time", total_sec, 3, es);
if (planstate->instrument->need_timer)
{
ExplainPropertyFloat("Actual Startup Time", startup_sec, 3, es);
ExplainPropertyFloat("Actual Total Time", total_sec, 3, es);
}
ExplainPropertyFloat("Actual Rows", rows, 0, es);
ExplainPropertyFloat("Actual Loops", nloops, 0, es);
}
}
else if (es->analyze)
{
if (es->format == EXPLAIN_FORMAT_TEXT)
appendStringInfo(es->str, " (never executed)");
else
else if (planstate->instrument->need_timer)
{
ExplainPropertyFloat("Actual Startup Time", 0.0, 3, es);
ExplainPropertyFloat("Actual Total Time", 0.0, 3, es);
}
else
{
ExplainPropertyFloat("Actual Rows", 0.0, 0, es);
ExplainPropertyFloat("Actual Loops", 0.0, 0, es);
}
}
/* in text format, first line ends here */