Skip to content

Commit

Permalink
Rework EXPLAIN for planner's buffer usage.
Browse files Browse the repository at this point in the history 
Commit ce77abe allowed EXPLAIN (BUFFERS) to report the information
on buffer usage during planning phase. However three issues were
reported regarding this feature.

(1) Previously, EXPLAIN option BUFFERS required ANALYZE. So the query
    had to be actually executed by specifying ANALYZE even when we
    want to see only the planner's buffer usage. This was inconvenient
    especially when the query was write one like DELETE.

(2) EXPLAIN included the planner's buffer usage in summary
    information. So SUMMARY option had to be enabled to report that.
    Also this format was confusing.

(3) The output structure for planning information was not consistent
    between TEXT format and the others. For example, "Planning" tag
    was output in JSON format, but not in TEXT format.

For (1), this commit allows us to perform EXPLAIN (BUFFERS) without
ANALYZE to report the planner's buffer usage.

For (2), this commit changed EXPLAIN output so that the planner's
buffer usage is reported before summary information.

For (3), this commit made the output structure for planning
information more consistent between the formats.

Back-patch to v13 where the planner's buffer usage was allowed to
be reported in EXPLAIN.

Reported-by: Pierre Giraud, David Rowley
Author: Fujii Masao
Reviewed-by: David Rowley, Julien Rouhaud, Pierre Giraud
Discussion: https://postgr.es/m/07b226e6-fa49-687f-b110-b7c37572f69e@dalibo.com
  • Loading branch information
@MasaoFujii
MasaoFujii committed Aug 21, 2020
1 parent d259afa commit 9d701e6
Show file tree
Hide file tree
Showing 4 changed files with 77 additions and 29 deletions.
3 changes: 1 addition & 2 deletions doc/src/sgml/ref/explain.sgml
View file
Expand Up @@ -187,8 +187,7 @@ ROLLBACK;
query processing.
The number of blocks shown for an
upper-level node includes those used by all its child nodes. In text
format, only non-zero values are printed. This parameter may only be
used when <literal>ANALYZE</literal> is also enabled. It defaults to
format, only non-zero values are printed. It defaults to
<literal>FALSE</literal>.
</para>
</listitem>
Expand Down
46 changes: 23 additions & 23 deletions src/backend/commands/explain.c
View file
Expand Up @@ -116,7 +116,8 @@ static void show_instrumentation_count(const char *qlabel, int which,
static void show_foreignscan_info(ForeignScanState *fsstate, ExplainState *es);
static void show_eval_params(Bitmapset *bms_params, ExplainState *es);
static const char *explain_get_index_name(Oid indexId);
static void show_buffer_usage(ExplainState *es, const BufferUsage *usage);
static void show_buffer_usage(ExplainState *es, const BufferUsage *usage,
bool planning);
static void show_wal_usage(ExplainState *es, const WalUsage *usage);
static void ExplainIndexScanDetails(Oid indexid, ScanDirection indexorderdir,
ExplainState *es);
Expand Down Expand Up @@ -221,11 +222,6 @@ ExplainQuery(ParseState *pstate, ExplainStmt *stmt,
parser_errposition(pstate, opt->location)));
}

if (es->buffers && !es->analyze)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("EXPLAIN option BUFFERS requires ANALYZE")));

if (es->wal && !es->analyze)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
Expand Down Expand Up @@ -586,8 +582,13 @@ ExplainOnePlan(PlannedStmt *plannedstmt, IntoClause *into, ExplainState *es,
/* Create textual dump of plan tree */
ExplainPrintPlan(es, queryDesc);

if (es->summary && (planduration || bufusage))
/* Show buffer usage in planning */
if (bufusage)
{
ExplainOpenGroup("Planning", "Planning", true, es);
show_buffer_usage(es, bufusage, true);
ExplainCloseGroup("Planning", "Planning", true, es);
}

if (es->summary && planduration)
{
Expand All @@ -596,19 +597,6 @@ ExplainOnePlan(PlannedStmt *plannedstmt, IntoClause *into, ExplainState *es,
ExplainPropertyFloat("Planning Time", "ms", 1000.0 * plantime, 3, es);
}

/* Show buffer usage */
if (es->summary && bufusage)
{
if (es->format == EXPLAIN_FORMAT_TEXT)
es->indent++;
show_buffer_usage(es, bufusage);
if (es->format == EXPLAIN_FORMAT_TEXT)
es->indent--;
}

if (es->summary && (planduration || bufusage))
ExplainCloseGroup("Planning", "Planning", true, es);

/* Print info about runtime of triggers */
if (es->analyze)
ExplainPrintTriggers(es, queryDesc);
Expand Down Expand Up @@ -1996,7 +1984,7 @@ ExplainNode(PlanState *planstate, List *ancestors,

/* Show buffer/WAL usage */
if (es->buffers && planstate->instrument)
show_buffer_usage(es, &planstate->instrument->bufusage);
show_buffer_usage(es, &planstate->instrument->bufusage, false);
if (es->wal && planstate->instrument)
show_wal_usage(es, &planstate->instrument->walusage);

Expand All @@ -2015,7 +2003,7 @@ ExplainNode(PlanState *planstate, List *ancestors,

ExplainOpenWorker(n, es);
if (es->buffers)
show_buffer_usage(es, &instrument->bufusage);
show_buffer_usage(es, &instrument->bufusage, false);
if (es->wal)
show_wal_usage(es, &instrument->walusage);
ExplainCloseWorker(n, es);
Expand Down Expand Up @@ -3301,7 +3289,7 @@ explain_get_index_name(Oid indexId)
* Show buffer usage details.
*/
static void
show_buffer_usage(ExplainState *es, const BufferUsage *usage)
show_buffer_usage(ExplainState *es, const BufferUsage *usage, bool planning)
{
if (es->format == EXPLAIN_FORMAT_TEXT)
{
Expand All @@ -3317,6 +3305,15 @@ show_buffer_usage(ExplainState *es, const BufferUsage *usage)
usage->temp_blks_written > 0);
bool has_timing = (!INSTR_TIME_IS_ZERO(usage->blk_read_time) ||
!INSTR_TIME_IS_ZERO(usage->blk_write_time));
bool show_planning = (planning && (has_shared ||
has_local || has_temp || has_timing));

if (show_planning)
{
ExplainIndentText(es);
appendStringInfoString(es->str, "Planning:\n");
es->indent++;
}

/* Show only positive counter values. */
if (has_shared || has_local || has_temp)
Expand Down Expand Up @@ -3386,6 +3383,9 @@ show_buffer_usage(ExplainState *es, const BufferUsage *usage)
INSTR_TIME_GET_MILLISEC(usage->blk_write_time));
appendStringInfoChar(es->str, '\n');
}

if (show_planning)
es->indent--;
}
else
{
Expand Down
55 changes: 51 additions & 4 deletions src/test/regress/expected/explain.out
View file
Expand Up @@ -106,7 +106,6 @@ select explain_filter('explain (analyze, buffers, format json) select * from int
"Temp Written Blocks": N +
}, +
"Planning": { +
"Planning Time": N.N, +
"Shared Hit Blocks": N, +
"Shared Read Blocks": N, +
"Shared Dirtied Blocks": N, +
Expand All @@ -118,6 +117,7 @@ select explain_filter('explain (analyze, buffers, format json) select * from int
"Temp Read Blocks": N, +
"Temp Written Blocks": N +
}, +
"Planning Time": N.N, +
"Triggers": [ +
], +
"Execution Time": N.N +
Expand Down Expand Up @@ -155,7 +155,6 @@ select explain_filter('explain (analyze, buffers, format xml) select * from int8
<Temp-Written-Blocks>N</Temp-Written-Blocks> +
</Plan> +
<Planning> +
<Planning-Time>N.N</Planning-Time> +
<Shared-Hit-Blocks>N</Shared-Hit-Blocks> +
<Shared-Read-Blocks>N</Shared-Read-Blocks> +
<Shared-Dirtied-Blocks>N</Shared-Dirtied-Blocks>+
Expand All @@ -167,6 +166,7 @@ select explain_filter('explain (analyze, buffers, format xml) select * from int8
<Temp-Read-Blocks>N</Temp-Read-Blocks> +
<Temp-Written-Blocks>N</Temp-Written-Blocks> +
</Planning> +
<Planning-Time>N.N</Planning-Time> +
<Triggers> +
</Triggers> +
<Execution-Time>N.N</Execution-Time> +
Expand Down Expand Up @@ -201,7 +201,6 @@ select explain_filter('explain (analyze, buffers, format yaml) select * from int
Temp Read Blocks: N +
Temp Written Blocks: N +
Planning: +
Planning Time: N.N +
Shared Hit Blocks: N +
Shared Read Blocks: N +
Shared Dirtied Blocks: N +
Expand All @@ -212,10 +211,58 @@ select explain_filter('explain (analyze, buffers, format yaml) select * from int
Local Written Blocks: N +
Temp Read Blocks: N +
Temp Written Blocks: N +
Planning Time: N.N +
Triggers: +
Execution Time: N.N
(1 row)

select explain_filter('explain (buffers, format text) select * from int8_tbl i8');
explain_filter
---------------------------------------------------------
Seq Scan on int8_tbl i8 (cost=N.N..N.N rows=N width=N)
(1 row)

select explain_filter('explain (buffers, format json) select * from int8_tbl i8');
explain_filter
------------------------------------
[ +
{ +
"Plan": { +
"Node Type": "Seq Scan", +
"Parallel Aware": false, +
"Relation Name": "int8_tbl",+
"Alias": "i8", +
"Startup Cost": N.N, +
"Total Cost": N.N, +
"Plan Rows": N, +
"Plan Width": N, +
"Shared Hit Blocks": N, +
"Shared Read Blocks": N, +
"Shared Dirtied Blocks": N, +
"Shared Written Blocks": N, +
"Local Hit Blocks": N, +
"Local Read Blocks": N, +
"Local Dirtied Blocks": N, +
"Local Written Blocks": N, +
"Temp Read Blocks": N, +
"Temp Written Blocks": N +
}, +
"Planning": { +
"Shared Hit Blocks": N, +
"Shared Read Blocks": N, +
"Shared Dirtied Blocks": N, +
"Shared Written Blocks": N, +
"Local Hit Blocks": N, +
"Local Read Blocks": N, +
"Local Dirtied Blocks": N, +
"Local Written Blocks": N, +
"Temp Read Blocks": N, +
"Temp Written Blocks": N +
} +
} +
]
(1 row)

-- SETTINGS option
-- We have to ignore other settings that might be imposed by the environment,
-- so printing the whole Settings field unfortunately won't do.
Expand Down Expand Up @@ -402,7 +449,6 @@ select jsonb_pretty(
"Shared Written Blocks": 0 +
}, +
"Planning": { +
"Planning Time": 0.0, +
"Local Hit Blocks": 0, +
"Temp Read Blocks": 0, +
"Local Read Blocks": 0, +
Expand All @@ -416,6 +462,7 @@ select jsonb_pretty(
}, +
"Triggers": [ +
], +
"Planning Time": 0.0, +
"Execution Time": 0.0 +
} +
]
Expand Down
2 changes: 2 additions & 0 deletions src/test/regress/sql/explain.sql
View file
Expand Up @@ -57,6 +57,8 @@ select explain_filter('explain (analyze, buffers, format text) select * from int
select explain_filter('explain (analyze, buffers, format json) select * from int8_tbl i8');
select explain_filter('explain (analyze, buffers, format xml) select * from int8_tbl i8');
select explain_filter('explain (analyze, buffers, format yaml) select * from int8_tbl i8');
select explain_filter('explain (buffers, format text) select * from int8_tbl i8');
select explain_filter('explain (buffers, format json) select * from int8_tbl i8');

-- SETTINGS option
-- We have to ignore other settings that might be imposed by the environment,
Expand Down

0 comments on commit 9d701e6

Please sign in to comment.