Rework EXPLAIN for planner's buffer usage.

Commit ce77abe63c 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

diff --git a/doc/src/sgml/ref/explain.sgml b/doc/src/sgml/ref/explain.sgml
index 1c19e254dc240b497df39bcf42d2e7b8ff6f8d37..906b2ccd50a2f3a2ba218e8ea69403ebe25001bc 100644 (file)
--- a/doc/src/sgml/ref/explain.sgml
+++ b/doc/src/sgml/ref/explain.sgml
@@ -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 ANALYZE is also enabled.  It defaults to
+      format, only non-zero values are printed.  It defaults to
       FALSE.
      
     

diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 30e0a7ee7f2190f8c9fad0d1308df410bc0e91d8..c98c9b5547c5a5a08fa98040f239bb13a85a54ae 100644 (file)
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -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);
@@ -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),
@@ -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)
    {
@@ -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);
@@ -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);
 
@@ -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);
@@ -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)
    {
@@ -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)
@@ -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
    {

diff --git a/src/test/regress/expected/explain.out b/src/test/regress/expected/explain.out
index 96baba038c2e2d0720ffe4e2ebb969232054bdfa..a1ee6c6792560d8eea94b6f9641b4c27292f4304 100644 (file)
--- a/src/test/regress/expected/explain.out
+++ b/src/test/regress/expected/explain.out
@@ -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, +
@@ -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         +
@@ -155,7 +155,6 @@ select explain_filter('explain (analyze, buffers, format xml) select * from int8
        N    +
                                                 +
                                              +
-       N.N              +
        N        +
        N      +
        N+
@@ -167,6 +166,7 @@ select explain_filter('explain (analyze, buffers, format xml) select * from int8
        N          +
        N    +
                                             +
+     N.N                +
                                              +
                                             +
      N.N              +
@@ -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 +
@@ -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.
@@ -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,                        +
@@ -416,6 +462,7 @@ select jsonb_pretty(
          },                                                 +
          "Triggers": [                                      +
          ],                                                 +
+         "Planning Time": 0.0,                              +
          "Execution Time": 0.0                              +
      }                                                      +
  ]

diff --git a/src/test/regress/sql/explain.sql b/src/test/regress/sql/explain.sql
index dce2a34207246a5cc99e0b4b6f923321757dd2f1..01783c607aa06ae9bdf7df81775a523928210c77 100644 (file)
--- a/src/test/regress/sql/explain.sql
+++ b/src/test/regress/sql/explain.sql
@@ -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,