Introduce field tracking cached plan type in PlannedStmt

PlannedStmt gains a new field, called CachedPlanType, able to track if a
given plan tree originates from the cache and if we are dealing with a
generic or custom cached plan.

This field can be used for monitoring or statistical purposes, in the
executor hooks, for example, based on the planned statement attached to
a QueryDesc.  A patch is under discussion for pg_stat_statements to
provide an equivalent of the counters in pg_prepared_statements for
custom and generic plans, to provide a more global view of such data, as
this data is now restricted to the current session.

The concept introduced in this commit is useful on its own, and has been
extracted from a larger patch by the same author.

Author: Sami Imseih <samimseih@gmail.com>
Reviewed-by: Andrei Lepikhov <lepihov@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/CAA5RZ0uFw8Y9GCFvafhC=OA8NnMqVZyzXPfv_EePOt+iv1T-qQ@mail.gmail.com

9 files changed, 33 insertions, 0 deletions

diff --git a/src/backend/commands/foreigncmds.c b/src/backend/commands/foreigncmds.c
index 8d2d7431544..fcd5fcd8915 100644
--- a/src/backend/commands/foreigncmds.c
+++ b/src/backend/commands/foreigncmds.c
@@ -1588,6 +1588,7 @@ ImportForeignSchema(ImportForeignSchemaStmt *stmt)
 			pstmt->utilityStmt = (Node *) cstmt;
 			pstmt->stmt_location = rs->stmt_location;
 			pstmt->stmt_len = rs->stmt_len;
+			pstmt->cached_plan_type = PLAN_CACHE_NONE;
 
 			/* Execute statement */
 			ProcessUtility(pstmt, cmd, false,
diff --git a/src/backend/commands/schemacmds.c b/src/backend/commands/schemacmds.c
index 546160f0941..c00f1a11384 100644
--- a/src/backend/commands/schemacmds.c
+++ b/src/backend/commands/schemacmds.c
@@ -215,6 +215,7 @@ CreateSchemaCommand(CreateSchemaStmt *stmt, const char *queryString,
 		wrapper->utilityStmt = stmt;
 		wrapper->stmt_location = stmt_location;
 		wrapper->stmt_len = stmt_len;
+		wrapper->cached_plan_type = PLAN_CACHE_NONE;
 
 		/* do this step */
 		ProcessUtility(wrapper,
diff --git a/src/backend/executor/execParallel.c b/src/backend/executor/execParallel.c
index f3e77bda279..fc76f22fb82 100644
--- a/src/backend/executor/execParallel.c
+++ b/src/backend/executor/execParallel.c
@@ -189,6 +189,7 @@ ExecSerializePlan(Plan *plan, EState *estate)
 	pstmt->permInfos = estate->es_rteperminfos;
 	pstmt->resultRelations = NIL;
 	pstmt->appendRelations = NIL;
+	pstmt->cached_plan_type = PLAN_CACHE_NONE;
 
 	/*
 	 * Transfer only parallel-safe subplans, leaving a NULL "hole" in the list
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index c989e72cac5..a77b2147e95 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -582,6 +582,7 @@ standard_planner(Query *parse, const char *query_string, int cursorOptions,
 	result->utilityStmt = parse->utilityStmt;
 	result->stmt_location = parse->stmt_location;
 	result->stmt_len = parse->stmt_len;
+	result->cached_plan_type = PLAN_CACHE_NONE;
 
 	result->jitFlags = PGJIT_NONE;
 	if (jit_enabled && jit_above_cost >= 0 &&
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 2f8c3d5f918..a297606cdd7 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -988,6 +988,7 @@ pg_plan_queries(List *querytrees, const char *query_string, int cursorOptions,
 			stmt->stmt_location = query->stmt_location;
 			stmt->stmt_len = query->stmt_len;
 			stmt->queryId = query->queryId;
+			stmt->cached_plan_type = PLAN_CACHE_NONE;
 		}
 		else
 		{
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 4c1faf5575c..babc34d0cbe 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -1234,6 +1234,7 @@ ProcessUtilitySlow(ParseState *pstate,
 							wrapper->utilityStmt = stmt;
 							wrapper->stmt_location = pstmt->stmt_location;
 							wrapper->stmt_len = pstmt->stmt_len;
+							wrapper->cached_plan_type = PLAN_CACHE_NONE;
 
 							ProcessUtility(wrapper,
 										   queryString,
@@ -1964,6 +1965,7 @@ ProcessUtilityForAlterTable(Node *stmt, AlterTableUtilityContext *context)
 	wrapper->utilityStmt = stmt;
 	wrapper->stmt_location = context->pstmt->stmt_location;
 	wrapper->stmt_len = context->pstmt->stmt_len;
+	wrapper->cached_plan_type = PLAN_CACHE_NONE;
 
 	ProcessUtility(wrapper,
 				   context->queryString,
diff --git a/src/backend/utils/cache/plancache.c b/src/backend/utils/cache/plancache.c
index 89a1c79e984..f4d2b9458a5 100644
--- a/src/backend/utils/cache/plancache.c
+++ b/src/backend/utils/cache/plancache.c
@@ -1283,6 +1283,7 @@ GetCachedPlan(CachedPlanSource *plansource, ParamListInfo boundParams,
 	CachedPlan *plan = NULL;
 	List	   *qlist;
 	bool		customplan;
+	ListCell   *lc;
 
 	/* Assert caller is doing things in a sane order */
 	Assert(plansource->magic == CACHEDPLANSOURCE_MAGIC);
@@ -1385,6 +1386,13 @@ GetCachedPlan(CachedPlanSource *plansource, ParamListInfo boundParams,
 		plan->is_saved = true;
 	}
 
+	foreach(lc, plan->stmt_list)
+	{
+		PlannedStmt *pstmt = (PlannedStmt *) lfirst(lc);
+
+		pstmt->cached_plan_type = customplan ? PLAN_CACHE_CUSTOM : PLAN_CACHE_GENERIC;
+	}
+
 	return plan;
 }
 
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 4f59e30d62d..46e2e09ea35 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -29,6 +29,20 @@
  */
 
 /* ----------------
+ *		CachedPlanType
+ *
+ * CachedPlanType identifies whether a PlannedStmt is a cached plan, and if
+ * so, whether it is generic or custom.
+ * ----------------
+ */
+typedef enum CachedPlanType
+{
+	PLAN_CACHE_NONE = 0,		/* Not a cached plan */
+	PLAN_CACHE_GENERIC,			/* Generic cached plan */
+	PLAN_CACHE_CUSTOM,			/* Custom cached plan */
+} CachedPlanType;
+
+/* ----------------
  *		PlannedStmt node
  *
  * The output of the planner is a Plan tree headed by a PlannedStmt node.
@@ -58,6 +72,9 @@ typedef struct PlannedStmt
 	/* plan identifier (can be set by plugins) */
 	int64		planId;
 
+	/* type of cached plan */
+	CachedPlanType cached_plan_type;
+
 	/* is it insert|update|delete|merge RETURNING? */
 	bool		hasReturning;
 
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index a8656419cb6..4353befab99 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -391,6 +391,7 @@ CachedFunctionHashEntry
 CachedFunctionHashKey
 CachedPlan
 CachedPlanSource
+CachedPlanType
 CallContext
 CallStmt
 CancelRequestPacket