0007-Expose-counters-of-plancache-to-pg_prepared_statement.patch

From e417fc58d51ab0c06de34a563d580c7d4017a1db Mon Sep 17 00:00:00 2001
From: Atsushi Torikoshi <torikoshia@oss.nttdata.com>
Date: Tue, 14 Jul 2020 20:57:16 +0900
Subject: [PATCH] We didn't have an easy way to find how many times generic and
 custom plans of a prepared statement have been executed. This patch exposes
 the numbers of both plans in pg_prepared_statements.

---
 doc/src/sgml/catalogs.sgml            | 18 ++++++++++
 src/backend/commands/prepare.c        | 15 +++++---
 src/backend/utils/cache/plancache.c   | 17 +++++----
 src/include/catalog/pg_proc.dat       |  6 ++--
 src/include/utils/plancache.h         |  3 +-
 src/test/regress/expected/prepare.out | 51 +++++++++++++++++++++++++++
 src/test/regress/expected/rules.out   |  6 ++--
 src/test/regress/sql/prepare.sql      | 15 ++++++++
 8 files changed, 115 insertions(+), 16 deletions(-)

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index e9cdff4864..8bc6d685f4 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -10830,6 +10830,24 @@ 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>
diff --git a/src/backend/commands/prepare.c b/src/backend/commands/prepare.c
index 80d6df8ac1..4b18be5b27 100644
--- a/src/backend/commands/prepare.c
+++ b/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);
 		}
diff --git a/src/backend/utils/cache/plancache.c b/src/backend/utils/cache/plancache.c
index 75b475c179..50d6ad28b4 100644
--- a/src/backend/utils/cache/plancache.c
+++ b/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);
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 95604e988a..4b5af32440 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/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',
diff --git a/src/include/utils/plancache.h b/src/include/utils/plancache.h
index 522020d763..4901568553 100644
--- a/src/include/utils/plancache.h
+++ b/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;
 
 /*
diff --git a/src/test/regress/expected/prepare.out b/src/test/regress/expected/prepare.out
index 3306c696b1..57b5272574 100644
--- a/src/test/regress/expected/prepare.out
+++ b/src/test/regress/expected/prepare.out
@@ -58,12 +58,63 @@ SELECT name, statement, parameter_types FROM pg_prepared_statements;
 PREPARE q2(text) AS
 	SELECT datname, datistemplate, datallowconn
 	FROM pg_database WHERE datname = $1;
+-- the view should return the inital state
+SELECT name, generic_plans, custom_plans from pg_prepared_statements;
+ name | generic_plans | custom_plans 
+------+---------------+--------------
+ q2   |             0 |            0
+(1 row)
+
+EXECUTE q2('postgres');
+ datname  | datistemplate | datallowconn 
+----------+---------------+--------------
+ postgres | f             | t
+(1 row)
+
+EXECUTE q2('postgres');
+ datname  | datistemplate | datallowconn 
+----------+---------------+--------------
+ postgres | f             | t
+(1 row)
+
+EXECUTE q2('postgres');
+ datname  | datistemplate | datallowconn 
+----------+---------------+--------------
+ postgres | f             | t
+(1 row)
+
+EXECUTE q2('postgres');
+ datname  | datistemplate | datallowconn 
+----------+---------------+--------------
+ postgres | f             | t
+(1 row)
+
+EXECUTE q2('postgres');
+ datname  | datistemplate | datallowconn 
+----------+---------------+--------------
+ postgres | f             | t
+(1 row)
+
+-- until here, all the plans are custom
+SELECT name, generic_plans, custom_plans from pg_prepared_statements;
+ name | generic_plans | custom_plans 
+------+---------------+--------------
+ q2   |             0 |            5
+(1 row)
+
 EXECUTE q2('postgres');
  datname  | datistemplate | datallowconn 
 ----------+---------------+--------------
  postgres | f             | t
 (1 row)
 
+-- latest plan shoud be generic
+SELECT name, generic_plans, custom_plans from pg_prepared_statements;
+ name | generic_plans | custom_plans 
+------+---------------+--------------
+ q2   |             1 |            5
+(1 row)
+
 PREPARE q3(text, int, float, boolean, smallint) AS
 	SELECT * FROM tenk1 WHERE string4 = $1 AND (four = $2 OR
 	ten = $3::bigint OR true = $4 OR odd = $5::int)
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index fa436f2caa..601734a6f1 100644
--- a/src/test/regress/expected/rules.out
+++ b/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,
diff --git a/src/test/regress/sql/prepare.sql b/src/test/regress/sql/prepare.sql
index 985d0f05c9..8a4b546b97 100644
--- a/src/test/regress/sql/prepare.sql
+++ b/src/test/regress/sql/prepare.sql
@@ -34,8 +34,23 @@ PREPARE q2(text) AS
 	SELECT datname, datistemplate, datallowconn
 	FROM pg_database WHERE datname = $1;
 
+-- the view should return the inital state
+SELECT name, generic_plans, custom_plans from pg_prepared_statements;
+
+EXECUTE q2('postgres');
+EXECUTE q2('postgres');
+EXECUTE q2('postgres');
+EXECUTE q2('postgres');
 EXECUTE q2('postgres');
 
+-- until here, all the plans are custom
+SELECT name, generic_plans, custom_plans from pg_prepared_statements;
+
+EXECUTE q2('postgres');
+
+-- latest plan shoud be generic
+SELECT name, generic_plans, custom_plans from pg_prepared_statements;
+
 PREPARE q3(text, int, float, boolean, smallint) AS
 	SELECT * FROM tenk1 WHERE string4 = $1 AND (four = $2 OR
 	ten = $3::bigint OR true = $4 OR odd = $5::int)
-- 
2.18.1