Include information on buffer usage during planning phase, in EXPLAIN output.

When BUFFERS option is enabled, EXPLAIN command includes the information
on buffer usage during each plan node, in its output. In addition to that,
this commit makes EXPLAIN command include also the information on
buffer usage during planning phase, in its output. This feature makes it
easier to discern the cases where lots of buffer access happen during
planning.

Author: Julien Rouhaud, slightly revised by Fujii Masao
Reviewed-by: Justin Pryzby
Discussion: https://postgr.es/m/16109-26a1a88651e90608@postgresql.org

src/backend/commands/explain.c

@@ -372,7 +372,11 @@ ExplainOneQuery(Query *query, int cursorOptions,
 		PlannedStmt *plan;
 		instr_time	planstart,
 					planduration;
+		BufferUsage bufusage_start,
+					bufusage;
 
+		if (es->buffers)
+			bufusage_start = pgBufferUsage;
 		INSTR_TIME_SET_CURRENT(planstart);
 
 		/* plan the query */
@@ -381,9 +385,16 @@ ExplainOneQuery(Query *query, int cursorOptions,
 		INSTR_TIME_SET_CURRENT(planduration);
 		INSTR_TIME_SUBTRACT(planduration, planstart);
 
+		/* calc differences of buffer counters. */
+		if (es->buffers)
+		{
+			memset(&bufusage, 0, sizeof(BufferUsage));
+			BufferUsageAccumDiff(&bufusage, &pgBufferUsage, &bufusage_start);
+		}
+
 		/* run it (if needed) and produce output */
 		ExplainOnePlan(plan, into, es, queryString, params, queryEnv,
-					   &planduration);
+					   &planduration, (es->buffers ? &bufusage : NULL));
 	}
 }
 
@@ -476,7 +487,8 @@ ExplainOneUtility(Node *utilityStmt, IntoClause *into, ExplainState *es,
 void
 ExplainOnePlan(PlannedStmt *plannedstmt, IntoClause *into, ExplainState *es,
 			   const char *queryString, ParamListInfo params,
-			   QueryEnvironment *queryEnv, const instr_time *planduration)
+			   QueryEnvironment *queryEnv, const instr_time *planduration,
+			   const BufferUsage *bufusage)
 {
 	DestReceiver *dest;
 	QueryDesc  *queryDesc;
@@ -560,6 +572,9 @@ ExplainOnePlan(PlannedStmt *plannedstmt, IntoClause *into, ExplainState *es,
 	/* Create textual dump of plan tree */
 	ExplainPrintPlan(es, queryDesc);
 
+	if (es->summary && (planduration || bufusage))
+		ExplainOpenGroup("Planning", "Planning", true, es);
+
 	if (es->summary && planduration)
 	{
 		double		plantime = INSTR_TIME_GET_DOUBLE(*planduration);
@@ -567,6 +582,19 @@ 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);

src/backend/commands/prepare.c

@@ -616,7 +616,11 @@ ExplainExecuteQuery(ExecuteStmt *execstmt, IntoClause *into, ExplainState *es,
 	EState	   *estate = NULL;
 	instr_time	planstart;
 	instr_time	planduration;
+	BufferUsage bufusage_start,
+				bufusage;
 
+	if (es->buffers)
+		bufusage_start = pgBufferUsage;
 	INSTR_TIME_SET_CURRENT(planstart);
 
 	/* Look it up in the hash table */
@@ -654,6 +658,13 @@ ExplainExecuteQuery(ExecuteStmt *execstmt, IntoClause *into, ExplainState *es,
 	INSTR_TIME_SET_CURRENT(planduration);
 	INSTR_TIME_SUBTRACT(planduration, planstart);
 
+	/* calc differences of buffer counters. */
+	if (es->buffers)
+	{
+		memset(&bufusage, 0, sizeof(BufferUsage));
+		BufferUsageAccumDiff(&bufusage, &pgBufferUsage, &bufusage_start);
+	}
+
 	plan_list = cplan->stmt_list;
 
 	/* Explain each query */
@@ -663,7 +674,7 @@ ExplainExecuteQuery(ExecuteStmt *execstmt, IntoClause *into, ExplainState *es,
 
 		if (pstmt->commandType != CMD_UTILITY)
 			ExplainOnePlan(pstmt, into, es, query_string, paramLI, queryEnv,
-						   &planduration);
+						   &planduration, (es->buffers ? &bufusage : NULL));
 		else
 			ExplainOneUtility(pstmt->utilityStmt, into, es, query_string,
 							  paramLI, queryEnv);

src/include/commands/explain.h

@@ -89,7 +89,8 @@ extern void ExplainOneUtility(Node *utilityStmt, IntoClause *into,
 extern void ExplainOnePlan(PlannedStmt *plannedstmt, IntoClause *into,
 						   ExplainState *es, const char *queryString,
 						   ParamListInfo params, QueryEnvironment *queryEnv,
-						   const instr_time *planduration);
+						   const instr_time *planduration,
+						   const BufferUsage *bufusage);
 
 extern void ExplainPrintPlan(ExplainState *es, QueryDesc *queryDesc);
 extern void ExplainPrintTriggers(ExplainState *es, QueryDesc *queryDesc);

src/test/regress/expected/explain.out

@@ -105,7 +105,19 @@ select explain_filter('explain (analyze, buffers, format json) 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, +
+       "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    +
+     },                            +
      "Triggers": [                 +
      ],                            +
      "Execution Time": N.N         +
@@ -142,7 +154,19 @@ 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>    +
      </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>+
+       <Shared-Written-Blocks>N</Shared-Written-Blocks>+
+       <Local-Hit-Blocks>N</Local-Hit-Blocks>          +
+       <Local-Read-Blocks>N</Local-Read-Blocks>        +
+       <Local-Dirtied-Blocks>N</Local-Dirtied-Blocks>  +
+       <Local-Written-Blocks>N</Local-Written-Blocks>  +
+       <Temp-Read-Blocks>N</Temp-Read-Blocks>          +
+       <Temp-Written-Blocks>N</Temp-Written-Blocks>    +
+     </Planning>                                       +
      <Triggers>                                        +
      </Triggers>                                       +
      <Execution-Time>N.N</Execution-Time>              +
@@ -176,7 +200,18 @@ select explain_filter('explain (analyze, buffers, format yaml) select * from int
      Local Written Blocks: N  +
      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 +
+     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   +
    Triggers:                  +
    Execution Time: N.N
 (1 row)
@@ -366,9 +401,21 @@ select jsonb_pretty(
              "Shared Dirtied Blocks": 0,                    +
              "Shared Written Blocks": 0                     +
          },                                                 +
+         "Planning": {                                      +
+             "Planning Time": 0.0,                          +
+             "Local Hit Blocks": 0,                         +
+             "Temp Read Blocks": 0,                         +
+             "Local Read Blocks": 0,                        +
+             "Shared Hit Blocks": 0,                        +
+             "Shared Read Blocks": 0,                       +
+             "Temp Written Blocks": 0,                      +
+             "Local Dirtied Blocks": 0,                     +
+             "Local Written Blocks": 0,                     +
+             "Shared Dirtied Blocks": 0,                    +
+             "Shared Written Blocks": 0                     +
+         },                                                 +
          "Triggers": [                                      +
          ],                                                 +
-         "Planning Time": 0.0,                              +
          "Execution Time": 0.0                              +
      }                                                      +
  ]