Add generic_plans and custom_plans fields into pg_prepared_statements.

There was no easy way to find how many times generic and custom plans
have been executed for a prepared statement. This commit exposes those
numbers of times in pg_prepared_statements view.

Author: Atsushi Torikoshi, Kyotaro Horiguchi
Reviewed-by: Tatsuro Yamada, Masahiro Ikeda, Fujii Masao
Discussion: https://postgr.es/m/CACZ0uYHZ4M=NZpofH6JuPHeX=__5xcDELF8hT8_2T+R55w4RQw@mail.gmail.com

doc/src/sgml/catalogs.sgml

@@ -10841,6 +10841,24 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx
        frontend/backend protocol
       </para></entry>
      </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>generic_plans</structfield> <type>int8</type>
+      </para>
+      <para>
+       Number of times generic plan was chosen
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>custom_plans</structfield> <type>int8</type>
+      </para>
+      <para>
+       Number of times custom plan was chosen
+      </para></entry>
+     </row>
     </tbody>
    </tgroup>
   </table>

src/backend/commands/prepare.c

@@ -694,7 +694,8 @@ ExplainExecuteQuery(ExecuteStmt *execstmt, IntoClause *into, ExplainState *es,
 
 /*
  * This set returning function reads all the prepared statements and
- * returns a set of (name, statement, prepare_time, param_types, from_sql).
+ * returns a set of (name, statement, prepare_time, param_types, from_sql,
+ * generic_plans, custom_plans).
  */
 Datum
 pg_prepared_statement(PG_FUNCTION_ARGS)
@@ -723,7 +724,7 @@ pg_prepared_statement(PG_FUNCTION_ARGS)
 	 * build tupdesc for result tuples. This must match the definition of the
 	 * pg_prepared_statements view in system_views.sql
 	 */
-	tupdesc = CreateTemplateTupleDesc(5);
+	tupdesc = CreateTemplateTupleDesc(7);
 	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "name",
 					   TEXTOID, -1, 0);
 	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "statement",
@@ -734,6 +735,10 @@ pg_prepared_statement(PG_FUNCTION_ARGS)
 					   REGTYPEARRAYOID, -1, 0);
 	TupleDescInitEntry(tupdesc, (AttrNumber) 5, "from_sql",
 					   BOOLOID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 6, "generic_plans",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 7, "custom_plans",
+					   INT8OID, -1, 0);
 
 	/*
 	 * We put all the tuples into a tuplestore in one scan of the hashtable.
@@ -755,8 +760,8 @@ pg_prepared_statement(PG_FUNCTION_ARGS)
 		hash_seq_init(&hash_seq, prepared_queries);
 		while ((prep_stmt = hash_seq_search(&hash_seq)) != NULL)
 		{
-			Datum		values[5];
-			bool		nulls[5];
+			Datum		values[7];
+			bool		nulls[7];
 
 			MemSet(nulls, 0, sizeof(nulls));
 
@@ -766,6 +771,8 @@ pg_prepared_statement(PG_FUNCTION_ARGS)
 			values[3] = build_regtype_array(prep_stmt->plansource->param_types,
 											prep_stmt->plansource->num_params);
 			values[4] = BoolGetDatum(prep_stmt->from_sql);
+			values[5] = Int64GetDatumFast(prep_stmt->plansource->num_generic_plans);
+			values[6] = Int64GetDatumFast(prep_stmt->plansource->num_custom_plans);
 
 			tuplestore_putvalues(tupstore, tupdesc, values, nulls);
 		}

src/backend/utils/cache/plancache.c

@@ -218,6 +218,7 @@ CreateCachedPlan(RawStmt *raw_parse_tree,
 	plansource->generation = 0;
 	plansource->generic_cost = -1;
 	plansource->total_custom_cost = 0;
+	plansource->num_generic_plans = 0;
 	plansource->num_custom_plans = 0;
 
 	MemoryContextSwitchTo(oldcxt);
@@ -285,6 +286,7 @@ CreateOneShotCachedPlan(RawStmt *raw_parse_tree,
 	plansource->generation = 0;
 	plansource->generic_cost = -1;
 	plansource->total_custom_cost = 0;
+	plansource->num_generic_plans = 0;
 	plansource->num_custom_plans = 0;
 
 	return plansource;
@@ -1213,12 +1215,14 @@ GetCachedPlan(CachedPlanSource *plansource, ParamListInfo boundParams,
 	{
 		/* Build a custom plan */
 		plan = BuildCachedPlan(plansource, qlist, boundParams, queryEnv);
-		/* Accumulate total costs of custom plans, but 'ware overflow */
-		if (plansource->num_custom_plans < INT_MAX)
-		{
-			plansource->total_custom_cost += cached_plan_cost(plan, true);
-			plansource->num_custom_plans++;
-		}
+		/* Accumulate total costs of custom plans */
+		plansource->total_custom_cost += cached_plan_cost(plan, true);
+
+		plansource->num_custom_plans++;
+	}
+	else
+	{
+		plansource->num_generic_plans++;
 	}
 
 	Assert(plan != NULL);
@@ -1574,6 +1578,7 @@ CopyCachedPlan(CachedPlanSource *plansource)
 	/* We may as well copy any acquired cost knowledge */
 	newsource->generic_cost = plansource->generic_cost;
 	newsource->total_custom_cost = plansource->total_custom_cost;
+	newsource->num_generic_plans = plansource->num_generic_plans;
 	newsource->num_custom_plans = plansource->num_custom_plans;
 
 	MemoryContextSwitchTo(oldcxt);

src/include/catalog/pg_proc.dat

@@ -7755,9 +7755,9 @@
 { oid => '2510', descr => 'get the prepared statements for this session',
   proname => 'pg_prepared_statement', prorows => '1000', proretset => 't',
   provolatile => 's', proparallel => 'r', prorettype => 'record',
-  proargtypes => '', proallargtypes => '{text,text,timestamptz,_regtype,bool}',
-  proargmodes => '{o,o,o,o,o}',
-  proargnames => '{name,statement,prepare_time,parameter_types,from_sql}',
+  proargtypes => '', proallargtypes => '{text,text,timestamptz,_regtype,bool,int8,int8}',
+  proargmodes => '{o,o,o,o,o,o,o}',
+  proargnames => '{name,statement,prepare_time,parameter_types,from_sql,generic_plans,custom_plans}',
   prosrc => 'pg_prepared_statement' },
 { oid => '2511', descr => 'get the open cursors for this session',
   proname => 'pg_cursor', prorows => '1000', proretset => 't',

src/include/utils/plancache.h

@@ -130,7 +130,8 @@ typedef struct CachedPlanSource
 	/* State kept to help decide whether to use custom or generic plans: */
 	double		generic_cost;	/* cost of generic plan, or -1 if not known */
 	double		total_custom_cost;	/* total cost of custom plans so far */
-	int			num_custom_plans;	/* number of plans included in total */
+	int64		num_custom_plans;	/* # of custom plans included in total */
+	int64		num_generic_plans;	/* # of generic plans */
 } CachedPlanSource;
 
 /*

src/test/regress/expected/plancache.out

@@ -284,7 +284,15 @@ insert into test_mode select 1 from generate_series(1,1000) union all select 2;
 create index on test_mode (a);
 analyze test_mode;
 prepare test_mode_pp (int) as select count(*) from test_mode where a = $1;
+select name, generic_plans, custom_plans from pg_prepared_statements
+  where  name = 'test_mode_pp';
+     name     | generic_plans | custom_plans 
+--------------+---------------+--------------
+ test_mode_pp |             0 |            0
+(1 row)
+
 -- up to 5 executions, custom plan is used
+set plan_cache_mode to auto;
 explain (costs off) execute test_mode_pp(2);
                         QUERY PLAN                        
 ----------------------------------------------------------
@@ -293,6 +301,13 @@ explain (costs off) execute test_mode_pp(2);
          Index Cond: (a = 2)
 (3 rows)
 
+select name, generic_plans, custom_plans from pg_prepared_statements
+  where  name = 'test_mode_pp';
+     name     | generic_plans | custom_plans 
+--------------+---------------+--------------
+ test_mode_pp |             0 |            1
+(1 row)
+
 -- force generic plan
 set plan_cache_mode to force_generic_plan;
 explain (costs off) execute test_mode_pp(2);
@@ -303,6 +318,13 @@ explain (costs off) execute test_mode_pp(2);
          Filter: (a = $1)
 (3 rows)
 
+select name, generic_plans, custom_plans from pg_prepared_statements
+  where  name = 'test_mode_pp';
+     name     | generic_plans | custom_plans 
+--------------+---------------+--------------
+ test_mode_pp |             1 |            1
+(1 row)
+
 -- get to generic plan by 5 executions
 set plan_cache_mode to auto;
 execute test_mode_pp(1); -- 1x
@@ -329,12 +351,26 @@ execute test_mode_pp(1); -- 4x
   1000
 (1 row)
 
+select name, generic_plans, custom_plans from pg_prepared_statements
+  where  name = 'test_mode_pp';
+     name     | generic_plans | custom_plans 
+--------------+---------------+--------------
+ test_mode_pp |             1 |            5
+(1 row)
+
 execute test_mode_pp(1); -- 5x
  count 
 -------
   1000
 (1 row)
 
+select name, generic_plans, custom_plans from pg_prepared_statements
+  where  name = 'test_mode_pp';
+     name     | generic_plans | custom_plans 
+--------------+---------------+--------------
+ test_mode_pp |             2 |            5
+(1 row)
+
 -- we should now get a really bad plan
 explain (costs off) execute test_mode_pp(2);
          QUERY PLAN          
@@ -354,4 +390,11 @@ explain (costs off) execute test_mode_pp(2);
          Index Cond: (a = 2)
 (3 rows)
 
+select name, generic_plans, custom_plans from pg_prepared_statements
+  where  name = 'test_mode_pp';
+     name     | generic_plans | custom_plans 
+--------------+---------------+--------------
+ test_mode_pp |             3 |            6
+(1 row)
+
 drop table test_mode;

src/test/regress/expected/rules.out

@@ -1428,8 +1428,10 @@ pg_prepared_statements| SELECT p.name,
     p.statement,
     p.prepare_time,
     p.parameter_types,
-    p.from_sql
-   FROM pg_prepared_statement() p(name, statement, prepare_time, parameter_types, from_sql);
+    p.from_sql,
+    p.generic_plans,
+    p.custom_plans
+   FROM pg_prepared_statement() p(name, statement, prepare_time, parameter_types, from_sql, generic_plans, custom_plans);
 pg_prepared_xacts| SELECT p.transaction,
     p.gid,
     p.prepared,

src/test/regress/sql/plancache.sql

@@ -186,13 +186,20 @@ create index on test_mode (a);
 analyze test_mode;
 
 prepare test_mode_pp (int) as select count(*) from test_mode where a = $1;
+select name, generic_plans, custom_plans from pg_prepared_statements
+  where  name = 'test_mode_pp';
 
 -- up to 5 executions, custom plan is used
+set plan_cache_mode to auto;
 explain (costs off) execute test_mode_pp(2);
+select name, generic_plans, custom_plans from pg_prepared_statements
+  where  name = 'test_mode_pp';
 
 -- force generic plan
 set plan_cache_mode to force_generic_plan;
 explain (costs off) execute test_mode_pp(2);
+select name, generic_plans, custom_plans from pg_prepared_statements
+  where  name = 'test_mode_pp';
 
 -- get to generic plan by 5 executions
 set plan_cache_mode to auto;
@@ -200,7 +207,11 @@ execute test_mode_pp(1); -- 1x
 execute test_mode_pp(1); -- 2x
 execute test_mode_pp(1); -- 3x
 execute test_mode_pp(1); -- 4x
+select name, generic_plans, custom_plans from pg_prepared_statements
+  where  name = 'test_mode_pp';
 execute test_mode_pp(1); -- 5x
+select name, generic_plans, custom_plans from pg_prepared_statements
+  where  name = 'test_mode_pp';
 
 -- we should now get a really bad plan
 explain (costs off) execute test_mode_pp(2);
@@ -208,5 +219,7 @@ explain (costs off) execute test_mode_pp(2);
 -- but we can force a custom plan
 set plan_cache_mode to force_custom_plan;
 explain (costs off) execute test_mode_pp(2);
+select name, generic_plans, custom_plans from pg_prepared_statements
+  where  name = 'test_mode_pp';
 
 drop table test_mode;