Fixes: #5787 In prepared statements, map any unused parameters

to a generic type.

src/backend/distributed/executor/adaptive_executor.c

@@ -152,6 +152,7 @@
 #include "distributed/multi_partitioning_utils.h"
 #include "distributed/multi_physical_planner.h"
 #include "distributed/multi_server_executor.h"
+#include "distributed/param_utils.h"
 #include "distributed/placement_access.h"
 #include "distributed/placement_connection.h"
 #include "distributed/relation_access_tracking.h"
@@ -830,6 +831,19 @@ AdaptiveExecutor(CitusScanState *scanState)
 		distributedPlan->modLevel, taskList, excludeFromXact);
 
 	bool localExecutionSupported = true;
+
+	/*
+	 * In some rare cases, we have prepared statements that pass a parameter
+	 * and never used in the query, mark such parameters' type as Invalid(0),
+	 * which will be used later in ExtractParametersFromParamList() to map them
+	 * to a generic datatype. Skip for dynamic parameters.
+	 */
+	if (paramListInfo && !paramListInfo->paramFetch)
+	{
+		paramListInfo = copyParamList(paramListInfo);
+		MarkUnreferencedExternParams((Node *) job->jobQuery, paramListInfo);
+	}
+
 	DistributedExecution *execution = CreateDistributedExecution(
 		distributedPlan->modLevel,
 		taskList,

src/backend/distributed/utils/param_utils.c

@@ -0,0 +1,88 @@
+/*-------------------------------------------------------------------------
+ *
+ * param_utils.c
+ *	  Utilities to process paramaters.
+ *
+ * Copyright (c) Citus Data, Inc.
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <nodes/bitmapset.h>
+#include <nodes/nodeFuncs.h>
+#include <nodes/parsenodes.h>
+#include <nodes/params.h>
+#include <nodes/primnodes.h>
+#include <nodes/nodes.h>
+#include "distributed/param_utils.h"
+
+/*
+ * IsExternParamUsedInQuery returns true if the passed in paramId
+ * is used in the query, false otherwise.
+ */
+bool
+GetParamsUsedInQuery(Node *expression, Bitmapset **paramBitmap)
+{
+	if (expression == NULL)
+	{
+		return false;
+	}
+
+	if (IsA(expression, Param))
+	{
+		Param *param = (Param *) expression;
+		int paramId = param->paramid;
+
+		/* only care about user supplied parameters */
+		if (param->paramkind != PARAM_EXTERN)
+		{
+			return false;
+		}
+
+		/* Found a parameter, mark it in the bitmap and continue */
+		*paramBitmap = bms_add_member(*paramBitmap, paramId);
+
+		/* Continue searching */
+		return false;
+	}
+
+	/* keep traversing */
+	if (IsA(expression, Query))
+	{
+		return query_tree_walker((Query *) expression,
+								 GetParamsUsedInQuery,
+								 paramBitmap,
+								 0);
+	}
+	else
+	{
+		return expression_tree_walker(expression,
+									  GetParamsUsedInQuery,
+									  paramBitmap);
+	}
+}
+
+
+/*
+ * MarkUnreferencedExternParams marks parameter's type to zero if the
+ * parameter is not used in the query.
+ */
+void
+MarkUnreferencedExternParams(Node *expression, ParamListInfo boundParams)
+{
+	int parameterCount = boundParams->numParams;
+	Bitmapset *paramBitmap = NULL;
+
+	/* Fetch all parameters used in the query */
+	GetParamsUsedInQuery(expression, &paramBitmap);
+
+	/* Check for any missing parameters */
+	for (int parameterNum = 1; parameterNum <= parameterCount; parameterNum++)
+	{
+		if (!bms_is_member(parameterNum, paramBitmap))
+		{
+			boundParams->params[parameterNum - 1].ptype = 0;
+		}
+	}
+}

src/include/distributed/param_utils.h

@@ -0,0 +1,15 @@
+/*-------------------------------------------------------------------------
+ * param_utils.h
+ *
+ * Copyright (c) Citus Data, Inc.
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef PARAM_UTILS_H
+#define PARAM_UTILS_H
+
+extern bool GetParamsUsedInQuery(Node *expression, Bitmapset **paramBitmap);
+extern void MarkUnreferencedExternParams(Node *expression, ParamListInfo boundParams);
+
+#endif /* PARAM_UTILS_H */

src/test/regress/expected/with_prepare.out

@@ -211,6 +211,24 @@ ORDER BY
 	user_id,
 	time
 LIMIT 10;
+--
+-- Test a prepared statement with unused argument
+--
+CREATE TYPE foo as (x int, y int);
+CREATE TABLE footest (x int, y int, z foo);
+SELECT create_distributed_table('footest','x');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+INSERT INTO footest VALUES(1, 2, (3,4));
+-- Add a redundant parameter
+PREPARE prepared_test_9(foo,foo) AS
+WITH a AS (
+	SELECT * FROM footest WHERE z = $1 AND x = 1 OFFSET 0
+)
+SELECT * FROM a;
 EXECUTE prepared_test_1;
  user_id |              time               | value_1 | value_2 | value_3 | value_4
 ---------------------------------------------------------------------
@@ -883,6 +901,42 @@ EXECUTE prepared_test_8;
 (10 rows)
 
 ROLLBACK;
+EXECUTE prepared_test_9('(3,4)','(2,3)');
+ x | y |   z
+---------------------------------------------------------------------
+ 1 | 2 | (3,4)
+(1 row)
+
+EXECUTE prepared_test_9('(3,4)','(2,3)');
+ x | y |   z
+---------------------------------------------------------------------
+ 1 | 2 | (3,4)
+(1 row)
+
+EXECUTE prepared_test_9('(3,4)','(2,3)');
+ x | y |   z
+---------------------------------------------------------------------
+ 1 | 2 | (3,4)
+(1 row)
+
+EXECUTE prepared_test_9('(3,4)','(2,3)');
+ x | y |   z
+---------------------------------------------------------------------
+ 1 | 2 | (3,4)
+(1 row)
+
+EXECUTE prepared_test_9('(3,4)','(2,3)');
+ x | y |   z
+---------------------------------------------------------------------
+ 1 | 2 | (3,4)
+(1 row)
+
+EXECUTE prepared_test_9('(3,4)','(2,3)');
+ x | y |   z
+---------------------------------------------------------------------
+ 1 | 2 | (3,4)
+(1 row)
+
 EXECUTE prepared_partition_column_insert(1);
  user_id | time | value_1 | value_2 | value_3 | value_4
 ---------------------------------------------------------------------

src/test/regress/sql/with_prepare.sql

@@ -225,6 +225,21 @@ ORDER BY
 	time
 LIMIT 10;
 
+--
+-- Test a prepared statement with unused argument
+--
+CREATE TYPE foo as (x int, y int);
+CREATE TABLE footest (x int, y int, z foo);
+SELECT create_distributed_table('footest','x');
+INSERT INTO footest VALUES(1, 2, (3,4));
+
+-- Add a redundant parameter
+PREPARE prepared_test_9(foo,foo) AS
+WITH a AS (
+	SELECT * FROM footest WHERE z = $1 AND x = 1 OFFSET 0
+)
+SELECT * FROM a;
+
 EXECUTE prepared_test_1;
 EXECUTE prepared_test_1;
 EXECUTE prepared_test_1;
@@ -301,6 +316,13 @@ EXECUTE prepared_test_8;
 EXECUTE prepared_test_8;
 ROLLBACK;
 
+EXECUTE prepared_test_9('(3,4)','(2,3)');
+EXECUTE prepared_test_9('(3,4)','(2,3)');
+EXECUTE prepared_test_9('(3,4)','(2,3)');
+EXECUTE prepared_test_9('(3,4)','(2,3)');
+EXECUTE prepared_test_9('(3,4)','(2,3)');
+EXECUTE prepared_test_9('(3,4)','(2,3)');
+
 EXECUTE prepared_partition_column_insert(1);
 EXECUTE prepared_partition_column_insert(2);
 EXECUTE prepared_partition_column_insert(3);