open-dsi
/
postgres
mirror of https://github.com/postgres/postgres
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

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

Browse Source 
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.
pull/1/head
Robert Haas 14 years ago
parent 1631598ea2
commit af7914c662
6 changed files with 97 additions and 22 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
Show Stats Download Patch File Download Diff File
  1. 17
      contrib/auto_explain/auto_explain.c
  2. 16
      doc/src/sgml/ref/explain.sgml
  3. 35
      src/backend/commands/explain.c
  4. 20
      src/backend/executor/instrument.c
  5. 1
      src/include/commands/explain.h
  6. 4
      src/include/executor/instrument.h

17
contrib/auto_explain/auto_explain.c
Unescape View File

@ -23,6 +23,7 @@ static int auto_explain_log_min_duration = -1; /* msec or -1 */
static bool auto_explain_log_analyze = false;
static bool auto_explain_log_verbose = false;
static bool auto_explain_log_buffers = false;
static bool auto_explain_log_timing = false;
static int auto_explain_log_format = EXPLAIN_FORMAT_TEXT;
static bool auto_explain_log_nested_statements = false;
@ -133,6 +134,17 @@ _PG_init(void)
NULL,
NULL);
DefineCustomBoolVariable("auto_explain.log_timing",
"Collect timing data, not just row counts.",
NULL,
&auto_explain_log_timing,
true,
PGC_SUSET,
0,
NULL,
NULL,
NULL);
EmitWarningsOnPlaceholders("auto_explain");
/* Install hooks. */
@ -170,7 +182,12 @@ explain_ExecutorStart(QueryDesc *queryDesc, int eflags)
/* Enable per-node instrumentation iff log_analyze is required. */
if (auto_explain_log_analyze && (eflags & EXEC_FLAG_EXPLAIN_ONLY) == 0)
{
if (auto_explain_log_timing)
queryDesc->instrument_options |= INSTRUMENT_TIMER;
else
queryDesc->instrument_options |= INSTRUMENT_ROWS;
if (auto_explain_log_buffers)
queryDesc->instrument_options |= INSTRUMENT_BUFFERS;
}

16
doc/src/sgml/ref/explain.sgml
Unescape View File

@ -40,6 +40,7 @@ EXPLAIN [ ANALYZE ] [ VERBOSE ] <replaceable class="parameter">statement</replac
VERBOSE [ <replaceable class="parameter">boolean</replaceable> ]
COSTS [ <replaceable class="parameter">boolean</replaceable> ]
BUFFERS [ <replaceable class="parameter">boolean</replaceable> ]
TIMING [ <replaceable class="parameter">boolean</replaceable> ]
FORMAT { TEXT | XML | JSON | YAML }
</synopsis>
</refsynopsisdiv>
@ -171,6 +172,21 @@ ROLLBACK;
</listitem>
</varlistentry>
<varlistentry>
<term><literal>TIMING</literal></term>
<listitem>
<para>
Include the actual startup time and time spent in the node in the output.
The overhead of repeatedly reading the system clock can slow down the
query significantly on some systems, so it may be useful to set this
parameter to <literal>FALSE</literal> when only actual row counts, and not
exact times, are needed.
This parameter may only be used when <literal>ANALYZE</literal> is also
enabled. It defaults to <literal>TRUE</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>FORMAT</literal></term>
<listitem>

35
src/backend/commands/explain.c
Unescape View File

@ -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);
@ -163,6 +169,15 @@ ExplainQuery(ExplainStmt *stmt, const char *queryString,
(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
* rewriter. We do not do AcquireRewriteLocks: we assume the query either
@ -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)
{
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
{
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 */

20
src/backend/executor/instrument.c
Unescape View File

@ -29,17 +29,19 @@ InstrAlloc(int n, int instrument_options)
{
Instrumentation *instr;
/* timer is always required for now */
Assert(instrument_options & INSTRUMENT_TIMER);
/* initialize all fields to zeroes, then modify as needed */
instr = palloc0(n * sizeof(Instrumentation));
if (instrument_options & INSTRUMENT_BUFFERS)
if (instrument_options & (INSTRUMENT_BUFFERS | INSTRUMENT_TIMER))
{
int i;
bool need_buffers = instrument_options & INSTRUMENT_BUFFERS;
bool need_timer = instrument_options & INSTRUMENT_TIMER;
for (i = 0; i < n; i++)
instr[i].need_bufusage = true;
{
instr[i].need_bufusage = need_buffers;
instr[i].need_timer = need_timer;
}
}
return instr;
@ -49,7 +51,7 @@ InstrAlloc(int n, int instrument_options)
void
InstrStartNode(Instrumentation *instr)
{
if (INSTR_TIME_IS_ZERO(instr->starttime))
if (instr->need_timer && INSTR_TIME_IS_ZERO(instr->starttime))
INSTR_TIME_SET_CURRENT(instr->starttime);
else
elog(DEBUG2, "InstrStartNode called twice in a row");
@ -68,6 +70,10 @@ InstrStopNode(Instrumentation *instr, double nTuples)
/* count the returned tuples */
instr->tuplecount += nTuples;
/* let's update the time only if the timer was requested */
if (instr->need_timer)
{
if (INSTR_TIME_IS_ZERO(instr->starttime))
{
elog(DEBUG2, "InstrStopNode called without start");
@ -79,6 +85,8 @@ InstrStopNode(Instrumentation *instr, double nTuples)
INSTR_TIME_SET_ZERO(instr->starttime);
}
/* Add delta of buffer usage since entry to node's totals */
if (instr->need_bufusage)
BufferUsageAccumDiff(&instr->bufusage,

1
src/include/commands/explain.h
Unescape View File

@ -31,6 +31,7 @@ typedef struct ExplainState
bool analyze; /* print actual times */
bool costs; /* print costs */
bool buffers; /* print buffer usage */
bool timing; /* print timing */
ExplainFormat format; /* output format */
/* other states */
PlannedStmt *pstmt; /* top of plan */

4
src/include/executor/instrument.h
Unescape View File

@ -31,14 +31,16 @@ typedef struct BufferUsage
/* Flag bits included in InstrAlloc's instrument_options bitmask */
typedef enum InstrumentOption
{
INSTRUMENT_TIMER = 1 << 0, /* needs timer */
INSTRUMENT_TIMER = 1 << 0, /* needs timer (and row counts) */
INSTRUMENT_BUFFERS = 1 << 1, /* needs buffer usage */
INSTRUMENT_ROWS = 1 << 2, /* needs row count */
INSTRUMENT_ALL = 0x7FFFFFFF
} InstrumentOption;
typedef struct Instrumentation
{
/* Parameters set at node creation: */
bool need_timer; /* TRUE if we need timer data */
bool need_bufusage; /* TRUE if we need buffer usage data */
/* Info about current plan cycle: */
bool running; /* TRUE if we've completed first tuple */

Write Preview
Loading…
Cancel
Save