MariaDB · drrtuy · Aug 9, 2026
diff --git a/include/mysql/plugin_function.h b/include/mysql/plugin_function.h
@@ -27,8 +27,20 @@
 
 #include <mysql/plugin.h>
 
+class Create_func;
+
 /*
   API for function plugins. (MariaDB_FUNCTION_PLUGIN)
+
+  An aggregate function's Create_func must create an Item_sum_plugin descendant.
+  Aggregate implementations use the normal Item_sum lifecycle and
+  aggregation_arg() to read values, including values replayed by DISTINCT. They
+  can implement supports_removal() and remove() for moving window frames, and
+  val_native() to preserve a pluggable result type.
+
+  The server keeps the function plugin and data type plugins referenced by an
+  Item_sum_plugin loaded for the lifetime of the prepared Item tree and its
+  execution copies.
 */
 #define MariaDB_FUNCTION_INTERFACE_VERSION (MYSQL_VERSION_ID << 8)
 

diff --git a/include/mysql/plugin_function.h.pp b/include/mysql/plugin_function.h.pp
@@ -714,6 +714,7 @@
                      const void *ha_data);
 void thd_wakeup_subsequent_commits(THD* thd, int wakeup_error);
 }
+class Create_func;
 class Plugin_function
 {
   int m_interface_version;

diff --git a/plugin/func_test/mysql-test/func_test/function_plugin.result b/plugin/func_test/mysql-test/func_test/function_plugin.result
@@ -0,0 +1,203 @@
+CREATE TABLE t1 (a INT, b INT);
+INSERT INTO t1 VALUES (1, 1), (2, 1), (NULL, 1), (3, 2);
+SELECT test_plugin_count(a) FROM t1;
+test_plugin_count(a)
+3
+SELECT b, test_plugin_count(a) FROM t1 GROUP BY b ORDER BY b;
+b	test_plugin_count(a)
+1	2
+2	1
+SELECT test_plugin_count(DISTINCT a) FROM
+(SELECT 1 AS a UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT NULL) dt;
+test_plugin_count(DISTINCT a)
+2
+SELECT test_plugin_count(a) FROM t1 WHERE FALSE;
+test_plugin_count(a)
+0
+SELECT test_plugin_count(a) FROM t1 WHERE a IS NULL;
+test_plugin_count(a)
+0
+SET @save_optimizer_switch= @@optimizer_switch;
+SET optimizer_switch= 'derived_merge=off';
+SELECT b, test_plugin_count(a)
+FROM (SELECT a, b FROM t1) AS dt
+GROUP BY b ORDER BY b;
+b	test_plugin_count(a)
+1	2
+2	1
+SET optimizer_switch= @save_optimizer_switch;
+PREPARE stmt FROM
+'SELECT test_plugin_count(a) FROM t1 WHERE b = ?';
+SET @b= 1;
+EXECUTE stmt USING @b;
+test_plugin_count(a)
+2
+SET @b= 2;
+EXECUTE stmt USING @b;
+test_plugin_count(a)
+1
+SET @b= 3;
+EXECUTE stmt USING @b;
+test_plugin_count(a)
+0
+DEALLOCATE PREPARE stmt;
+SELECT a, test_plugin_count(a) OVER (ORDER BY a) FROM t1 ORDER BY a;
+a	test_plugin_count(a) OVER (ORDER BY a)
+NULL	0
+1	1
+2	2
+3	3
+CREATE TABLE t_window (id INT, part INT, value INT);
+INSERT INTO t_window VALUES
+(1, 1, 10), (2, 1, NULL), (3, 1, 30), (4, 1, 40),
+(5, 2, NULL), (6, 2, 60);
+SELECT id, part, value,
+test_plugin_count(value) OVER (
+PARTITION BY part ORDER BY id
+ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS cnt
+FROM t_window ORDER BY id;
+id	part	value	cnt
+1	1	10	1
+2	1	NULL	2
+3	1	30	2
+4	1	40	2
+5	2	NULL	1
+6	2	60	1
+SELECT test_plugin_count(DISTINCT a) OVER () FROM t1;
+ERROR 42000: This version of MariaDB doesn't yet support 'plugin aggregate with DISTINCT as window function'
+SELECT sysconst_test() OVER ();
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'OVER ()' at line 1
+SELECT strnxfrm(DISTINCT 'a', 1, 1, 0);
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '' at line 1
+CREATE TABLE t_uuid (id INT, grp INT, value UUID);
+INSERT INTO t_uuid VALUES
+(1, 1, NULL),
+(2, 1, '00000000-0000-0000-0000-000000000001'),
+(3, 2, '00000000-0000-0000-0000-000000000002'),
+(4, 2, NULL),
+(5, 3, NULL);
+SELECT test_plugin_first(value) FROM t_uuid WHERE grp = 1;
+test_plugin_first(value)
+00000000-0000-0000-0000-000000000001
+SELECT grp, test_plugin_first(value) FROM t_uuid GROUP BY grp ORDER BY grp;
+grp	test_plugin_first(value)
+1	00000000-0000-0000-0000-000000000001
+2	00000000-0000-0000-0000-000000000002
+3	NULL
+SELECT id, grp, test_plugin_first(value) OVER (
+PARTITION BY grp ORDER BY id
+ROWS BETWEEN CURRENT ROW AND 1 FOLLOWING) AS value
+FROM t_uuid ORDER BY id;
+id	grp	value
+1	1	00000000-0000-0000-0000-000000000001
+2	1	00000000-0000-0000-0000-000000000001
+3	2	00000000-0000-0000-0000-000000000002
+4	2	NULL
+5	3	NULL
+SELECT test_plugin_count(DISTINCT value) FROM t_uuid;
+test_plugin_count(DISTINCT value)
+2
+SELECT test_plugin_first(DISTINCT value) FROM
+(SELECT value FROM t_uuid WHERE id = 2
+UNION ALL
+SELECT value FROM t_uuid WHERE id = 2) AS dt;
+test_plugin_first(DISTINCT value)
+00000000-0000-0000-0000-000000000001
+SELECT test_plugin_first(DISTINCT value) =
+(SELECT value FROM t_uuid WHERE id = 2)
+FROM t_uuid WHERE grp = 1;
+test_plugin_first(DISTINCT value) =
+(SELECT value FROM t_uuid WHERE id = 2)
+1
+SELECT test_plugin_first(value) IS NULL FROM t_uuid WHERE FALSE;
+test_plugin_first(value) IS NULL
+1
+SELECT test_plugin_first(value) IS NULL FROM t_uuid WHERE grp = 3;
+test_plugin_first(value) IS NULL
+1
+SELECT test_plugin_first(value) =
+(SELECT value FROM t_uuid WHERE id = 2)
+FROM t_uuid WHERE grp = 1;
+test_plugin_first(value) =
+(SELECT value FROM t_uuid WHERE id = 2)
+1
+SET @save_optimizer_switch= @@optimizer_switch;
+SET optimizer_switch= 'derived_merge=off';
+SELECT value, value = (SELECT value FROM t_uuid WHERE id = 3)
+FROM
+(SELECT test_plugin_first(value) AS value
+FROM t_uuid WHERE grp = 2) AS dt;
+value	value = (SELECT value FROM t_uuid WHERE id = 3)
+00000000-0000-0000-0000-000000000002	1
+SET optimizer_switch= @save_optimizer_switch;
+CREATE TABLE t_uuid_aggregate AS
+SELECT grp, test_plugin_first(value) AS value
+FROM t_uuid GROUP BY grp;
+SHOW CREATE TABLE t_uuid_aggregate;
+Table	Create Table
+t_uuid_aggregate	CREATE TABLE `t_uuid_aggregate` (
+  `grp` int(11) DEFAULT NULL,
+  `value` uuid DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci
+SELECT * FROM t_uuid_aggregate ORDER BY grp;
+grp	value
+1	00000000-0000-0000-0000-000000000001
+2	00000000-0000-0000-0000-000000000002
+3	NULL
+CREATE TABLE t_uuid_result (value UUID);
+INSERT INTO t_uuid_result
+SELECT test_plugin_first(value) FROM t_uuid WHERE grp = 1;
+SELECT value, value = (SELECT value FROM t_uuid WHERE id = 2)
+FROM t_uuid_result;
+value	value = (SELECT value FROM t_uuid WHERE id = 2)
+00000000-0000-0000-0000-000000000001	1
+CREATE TABLE t_blob (value TEXT);
+INSERT INTO t_blob VALUES ('a'), ('a'), ('b'), (NULL);
+SELECT test_plugin_count(DISTINCT value) FROM t_blob;
+test_plugin_count(DISTINCT value)
+2
+SELECT test_plugin_first(DISTINCT value) IS NOT NULL FROM t_blob;
+test_plugin_first(DISTINCT value) IS NOT NULL
+1
+INSTALL SONAME 'type_test';
+PREPARE type_stmt FROM
+'SELECT test_plugin_first(CAST(1 AS test_int8))';
+UNINSTALL PLUGIN test_double;
+UNINSTALL PLUGIN test_int8;
+EXECUTE type_stmt;
+test_plugin_first(CAST(1 AS test_int8))
+1
+DEALLOCATE PREPARE type_stmt;
+INSTALL SONAME 'type_test';
+UNINSTALL SONAME 'type_test';
+DROP TABLE t_blob, t_uuid_result, t_uuid_aggregate, t_uuid, t_window;
+SELECT GET_LOCK('function_plugin_lock', 10);
+GET_LOCK('function_plugin_lock', 10)
+1
+connect  con1,localhost,root,,;
+connection con1;
+SELECT test_plugin_count(IF(GET_LOCK('function_plugin_lock', 10), a, a)) FROM t1;
+connection default;
+UNINSTALL SONAME 'func_test';
+Warnings:
+Warning	1620	Plugin is busy and will be uninstalled on shutdown
+SELECT RELEASE_LOCK('function_plugin_lock');
+RELEASE_LOCK('function_plugin_lock')
+1
+connection con1;
+test_plugin_count(IF(GET_LOCK('function_plugin_lock', 10), a, a))
+3
+disconnect con1;
+connection default;
+INSTALL SONAME 'func_test';
+PREPARE function_stmt FROM
+'SELECT test_plugin_count(a) FROM t1';
+UNINSTALL SONAME 'func_test';
+Warnings:
+Warning	1620	Plugin is busy and will be uninstalled on shutdown
+EXECUTE function_stmt;
+test_plugin_count(a)
+3
+DEALLOCATE PREPARE function_stmt;
+INSTALL SONAME 'func_test';
+DROP TABLE t1;
diff --git a/plugin/func_test/mysql-test/func_test/function_plugin.test b/plugin/func_test/mysql-test/func_test/function_plugin.test
@@ -0,0 +1,151 @@
+--source include/have_udf.inc
+
+--disable_query_log
+if (`SELECT COUNT(*) FROM INFORMATION_SCHEMA.PLUGINS
+    WHERE PLUGIN_NAME='test_plugin_count'`)
+{
+  UNINSTALL SONAME 'func_test';
+}
+INSTALL SONAME 'func_test';
+--enable_query_log
+
+CREATE TABLE t1 (a INT, b INT);
+INSERT INTO t1 VALUES (1, 1), (2, 1), (NULL, 1), (3, 2);
+
+SELECT test_plugin_count(a) FROM t1;
+SELECT b, test_plugin_count(a) FROM t1 GROUP BY b ORDER BY b;
+SELECT test_plugin_count(DISTINCT a) FROM
+  (SELECT 1 AS a UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT NULL) dt;
+SELECT test_plugin_count(a) FROM t1 WHERE FALSE;
+SELECT test_plugin_count(a) FROM t1 WHERE a IS NULL;
+
+SET @save_optimizer_switch= @@optimizer_switch;
+SET optimizer_switch= 'derived_merge=off';
+SELECT b, test_plugin_count(a)
+FROM (SELECT a, b FROM t1) AS dt
+GROUP BY b ORDER BY b;
+SET optimizer_switch= @save_optimizer_switch;
+
+PREPARE stmt FROM
+  'SELECT test_plugin_count(a) FROM t1 WHERE b = ?';
+SET @b= 1;
+EXECUTE stmt USING @b;
+SET @b= 2;
+EXECUTE stmt USING @b;
+SET @b= 3;
+EXECUTE stmt USING @b;
+DEALLOCATE PREPARE stmt;
+
+SELECT a, test_plugin_count(a) OVER (ORDER BY a) FROM t1 ORDER BY a;
+
+CREATE TABLE t_window (id INT, part INT, value INT);
+INSERT INTO t_window VALUES
+  (1, 1, 10), (2, 1, NULL), (3, 1, 30), (4, 1, 40),
+  (5, 2, NULL), (6, 2, 60);
+SELECT id, part, value,
+       test_plugin_count(value) OVER (
+         PARTITION BY part ORDER BY id
+         ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS cnt
+FROM t_window ORDER BY id;
+
+--error ER_NOT_SUPPORTED_YET
+SELECT test_plugin_count(DISTINCT a) OVER () FROM t1;
+
+--error ER_PARSE_ERROR
+SELECT sysconst_test() OVER ();
+--error ER_PARSE_ERROR
+SELECT strnxfrm(DISTINCT 'a', 1, 1, 0);
+
+CREATE TABLE t_uuid (id INT, grp INT, value UUID);
+INSERT INTO t_uuid VALUES
+  (1, 1, NULL),
+  (2, 1, '00000000-0000-0000-0000-000000000001'),
+  (3, 2, '00000000-0000-0000-0000-000000000002'),
+  (4, 2, NULL),
+  (5, 3, NULL);
+
+SELECT test_plugin_first(value) FROM t_uuid WHERE grp = 1;
+SELECT grp, test_plugin_first(value) FROM t_uuid GROUP BY grp ORDER BY grp;
+SELECT id, grp, test_plugin_first(value) OVER (
+         PARTITION BY grp ORDER BY id
+         ROWS BETWEEN CURRENT ROW AND 1 FOLLOWING) AS value
+FROM t_uuid ORDER BY id;
+SELECT test_plugin_count(DISTINCT value) FROM t_uuid;
+SELECT test_plugin_first(DISTINCT value) FROM
+  (SELECT value FROM t_uuid WHERE id = 2
+   UNION ALL
+   SELECT value FROM t_uuid WHERE id = 2) AS dt;
+SELECT test_plugin_first(DISTINCT value) =
+       (SELECT value FROM t_uuid WHERE id = 2)
+FROM t_uuid WHERE grp = 1;
+SELECT test_plugin_first(value) IS NULL FROM t_uuid WHERE FALSE;
+SELECT test_plugin_first(value) IS NULL FROM t_uuid WHERE grp = 3;
+SELECT test_plugin_first(value) =
+       (SELECT value FROM t_uuid WHERE id = 2)
+FROM t_uuid WHERE grp = 1;
+
+SET @save_optimizer_switch= @@optimizer_switch;
+SET optimizer_switch= 'derived_merge=off';
+SELECT value, value = (SELECT value FROM t_uuid WHERE id = 3)
+FROM
+  (SELECT test_plugin_first(value) AS value
+   FROM t_uuid WHERE grp = 2) AS dt;
+SET optimizer_switch= @save_optimizer_switch;
+
+CREATE TABLE t_uuid_aggregate AS
+  SELECT grp, test_plugin_first(value) AS value
+  FROM t_uuid GROUP BY grp;
+SHOW CREATE TABLE t_uuid_aggregate;
+SELECT * FROM t_uuid_aggregate ORDER BY grp;
+
+CREATE TABLE t_uuid_result (value UUID);
+INSERT INTO t_uuid_result
+  SELECT test_plugin_first(value) FROM t_uuid WHERE grp = 1;
+SELECT value, value = (SELECT value FROM t_uuid WHERE id = 2)
+FROM t_uuid_result;
+
+CREATE TABLE t_blob (value TEXT);
+INSERT INTO t_blob VALUES ('a'), ('a'), ('b'), (NULL);
+SELECT test_plugin_count(DISTINCT value) FROM t_blob;
+SELECT test_plugin_first(DISTINCT value) IS NOT NULL FROM t_blob;
+
+INSTALL SONAME 'type_test';
+PREPARE type_stmt FROM
+  'SELECT test_plugin_first(CAST(1 AS test_int8))';
+UNINSTALL PLUGIN test_double;
+UNINSTALL PLUGIN test_int8;
+EXECUTE type_stmt;
+DEALLOCATE PREPARE type_stmt;
+INSTALL SONAME 'type_test';
+UNINSTALL SONAME 'type_test';
+
+DROP TABLE t_blob, t_uuid_result, t_uuid_aggregate, t_uuid, t_window;
+SELECT GET_LOCK('function_plugin_lock', 10);
+--connect (con1,localhost,root,,)
+--connection con1
+--send SELECT test_plugin_count(IF(GET_LOCK('function_plugin_lock', 10), a, a)) FROM t1
+--connection default
+let $wait_condition=
+  SELECT COUNT(*) = 1 FROM INFORMATION_SCHEMA.PROCESSLIST
+  WHERE STATE = 'User lock' AND INFO LIKE 'SELECT test_plugin_count%';
+--source include/wait_condition.inc
+UNINSTALL SONAME 'func_test';
+SELECT RELEASE_LOCK('function_plugin_lock');
+--connection con1
+--reap
+--disconnect con1
+--connection default
+INSTALL SONAME 'func_test';
+
+PREPARE function_stmt FROM
+  'SELECT test_plugin_count(a) FROM t1';
+UNINSTALL SONAME 'func_test';
+EXECUTE function_stmt;
+DEALLOCATE PREPARE function_stmt;
+INSTALL SONAME 'func_test';
+DROP TABLE t1;
+--disable_query_log
+UNINSTALL SONAME 'func_test';
+INSTALL SONAME 'func_test';
+DELETE FROM mysql.plugin WHERE dl='func_test.so';
+--enable_query_log