cleanup: MDEV-11339 Implement native UUID4 function

- Moving the class UUIDv1 into a separate file sql_type_uuid_v1.h

- Adding a new class UUIDv4, similar to UUIDv1

- Changing the way how my_random_bytes() failures are handled.
  Instead of raising an error it now raises a note.
  Reasoning: if we're in the middle of a multi-million row
  transaction and one UUIDv4 generation fails, it's not a good
  idea to throw away the entire transaction. Instead, let's
  generate bytes using a my_rnd() loop.

- Adding a new test func_uuid_v4.test to demonstrate that the UUIDv4()
  returned type is "UUID NOT NULL".

- Adding a new test func_uuidv4_debug.test to emulate my_random_bytes()
  failures

- Adding a template Item_func_uuid_vx to share the code
  between the implementations of UUID() and UUIDv4().

plugin/type_uuid/item_uuidfunc.cc

-/* Copyright (c) 2019,2021, MariaDB Corporation
+/* Copyright (c) 2019,2024, MariaDB Corporation
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -29,31 +29,3 @@ String *Item_func_sys_guid::val_str(String *str)
   my_uuid2str(buf, const_cast<char*>(str->ptr()), 0);
   return str;
 }
-
-String *Item_func_uuid_v4::val_str(String *str)
-{
-  DBUG_ASSERT(fixed());
-  str->alloc(MY_UUID_STRING_LENGTH+1);
-  str->length(MY_UUID_STRING_LENGTH);
-  str->set_charset(collation.collation);
-
-  uchar buf[MY_UUID_SIZE];
-  if (!my_uuid_v4(buf)) {
-    my_error(ER_INTERNAL_ERROR, MYF(0),
-    "Failed to generate a random value for UUIDv4");
-  }
-  my_uuid2str(buf, const_cast<char*>(str->ptr()), 1);
-  return str;
-}
-
-bool Item_func_uuid_v4::val_native(THD *, Native *to)
-{
-  DBUG_ASSERT(fixed());
-  to->alloc(MY_UUID_SIZE);
-  to->length(MY_UUID_SIZE);
-  if (!my_uuid_v4((uchar*)to->ptr())) {
-    my_error(ER_INTERNAL_ERROR, MYF(0),
-    "Failed to generate a random value for UUIDv4");
-  }
-  return 0;
-}

plugin/type_uuid/item_uuidfunc.h

 #ifndef ITEM_UUIDFUNC_INCLUDED
 #define ITEM_UUIDFUNC_INCLUDED
 
-/* Copyright (c) 2019,2021, MariaDB Corporation
+/* Copyright (c) 2019,2024, MariaDB Corporation
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -18,7 +18,8 @@
 
 
 #include "item.h"
-#include "sql_type_uuid.h"
+#include "sql_type_uuid_v1.h"
+#include "sql_type_uuid_v4.h"
 
 class Item_func_sys_guid: public Item_str_func
 {
@@ -49,46 +50,54 @@ class Item_func_sys_guid: public Item_str_func
   { return get_item_copy<Item_func_sys_guid>(thd, this); }
 };
 
-class Item_func_uuid: public Type_handler_uuid_new::Item_fbt_func
+
+template<class UUIDvX>
+class Item_func_uuid_vx: public Type_handler_uuid_new::Item_fbt_func
 {
 public:
-  Item_func_uuid(THD *thd): Item_fbt_func(thd) { }
+  using Item_fbt_func::Item_fbt_func;
   bool const_item() const override { return false; }
   table_map used_tables() const override { return RAND_TABLE_BIT; }
   bool check_vcol_func_processor(void *arg) override
   {
     return mark_unsupported_function(func_name(), "()", arg, VCOL_NON_DETERMINISTIC);
   }
-  LEX_CSTRING func_name_cstring() const override
-  {
-    static LEX_CSTRING name= {STRING_WITH_LEN("uuid") };
-    return name;
-  }
   String *val_str(String *str) override
   {
     DBUG_ASSERT(fixed());
-    return UUIDv1().to_string(str) ? NULL : str;
+    return UUIDvX().to_string(str) ? NULL : str;
   }
   bool val_native(THD *thd, Native *to) override
   {
     DBUG_ASSERT(fixed());
-    return UUIDv1::construct_native(to);
+    return UUIDvX::construct_native(to);
+  }
+};
+
+
+class Item_func_uuid: public Item_func_uuid_vx<UUIDv1>
+{
+public:
+  using Item_func_uuid_vx::Item_func_uuid_vx;
+  LEX_CSTRING func_name_cstring() const override
+  {
+    static LEX_CSTRING name= {STRING_WITH_LEN("uuid") };
+    return name;
   }
   Item *do_get_copy(THD *thd) const override
   { return get_item_copy<Item_func_uuid>(thd, this); }
 };
 
-class Item_func_uuid_v4: public Item_func_uuid
+
+class Item_func_uuid_v4: public Item_func_uuid_vx<UUIDv4>
 {
 public:
-  Item_func_uuid_v4(THD *thd): Item_func_uuid(thd) { }
+  using Item_func_uuid_vx::Item_func_uuid_vx;
   LEX_CSTRING func_name_cstring() const override
   {
     static LEX_CSTRING name= {STRING_WITH_LEN("uuidv4") };
     return name;
   }
-  String *val_str(String *) override;
-  bool val_native(THD *thd, Native *to) override;
   Item *do_get_copy(THD *thd) const override
   { return get_item_copy<Item_func_uuid_v4>(thd, this); }
 };

plugin/type_uuid/mysql-test/type_uuid/func_uuid_v4.result

+#
+# MDEV-33827 UUID() returns a NULL-able result
+#
+CREATE TABLE t1 AS SELECT UUIDv4();
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `UUIDv4()` uuid NOT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci
+DROP TABLE t1;

plugin/type_uuid/mysql-test/type_uuid/func_uuid_v4.test

+--echo #
+--echo # MDEV-33827 UUID() returns a NULL-able result
+--echo #
+
+CREATE TABLE t1 AS SELECT UUIDv4();
+SHOW CREATE TABLE t1;
+DROP TABLE t1;

plugin/type_uuid/mysql-test/type_uuid/func_uuidv4_debug.result

+SET debug_dbug="+d,simulate_uuidv4_my_random_bytes_failure";
+#
+# Start of 11.6 tests
+#
+#
+# MDEV-11339 Support UUID v4 generation
+#
+CREATE TABLE t1 (
+a int primary key not null,
+u UUID DEFAULT UUIDv4(),
+unique key(u)
+);
+INSERT INTO t1(a) SELECT seq FROM seq_1_to_16;
+Warnings:
+Note	1105	UUIDv4 generation failed; using a my_rnd fallback
+Note	1105	UUIDv4 generation failed; using a my_rnd fallback
+Note	1105	UUIDv4 generation failed; using a my_rnd fallback
+Note	1105	UUIDv4 generation failed; using a my_rnd fallback
+Note	1105	UUIDv4 generation failed; using a my_rnd fallback
+Note	1105	UUIDv4 generation failed; using a my_rnd fallback
+Note	1105	UUIDv4 generation failed; using a my_rnd fallback
+Note	1105	UUIDv4 generation failed; using a my_rnd fallback
+Note	1105	UUIDv4 generation failed; using a my_rnd fallback
+Note	1105	UUIDv4 generation failed; using a my_rnd fallback
+Note	1105	UUIDv4 generation failed; using a my_rnd fallback
+Note	1105	UUIDv4 generation failed; using a my_rnd fallback
+Note	1105	UUIDv4 generation failed; using a my_rnd fallback
+Note	1105	UUIDv4 generation failed; using a my_rnd fallback
+Note	1105	UUIDv4 generation failed; using a my_rnd fallback
+Note	1105	UUIDv4 generation failed; using a my_rnd fallback
+SELECT COUNT(DISTINCT u) AS distinct_uuid_count FROM t1;
+distinct_uuid_count
+16
+SELECT
+u REGEXP '[a-f0-9]{8}-[a-f0-9]{4}-4[a-f0-9]{3}-[89aAbB][a-f0-9]{3}-[a-f0-9]{12}' AS is_correct_version_and_revision,
+COUNT(*)
+FROM t1 GROUP BY is_correct_version_and_revision;
+is_correct_version_and_revision	COUNT(*)
+1	16
+DROP TABLE t1;
+#
+# End of 11.6 tests
+#
+SET debug_dbug="";

plugin/type_uuid/mysql-test/type_uuid/func_uuidv4_debug.test

+--source include/have_debug.inc
+
+SET debug_dbug="+d,simulate_uuidv4_my_random_bytes_failure";
+
+source include/have_sequence.inc;
+
+--echo #
+--echo # Start of 11.6 tests
+--echo #
+
+--echo #
+--echo # MDEV-11339 Support UUID v4 generation
+--echo #
+
+CREATE TABLE t1 (
+  a int primary key not null,
+  u UUID DEFAULT UUIDv4(),
+  unique key(u)
+);
+INSERT INTO t1(a) SELECT seq FROM seq_1_to_16;
+SELECT COUNT(DISTINCT u) AS distinct_uuid_count FROM t1;
+SELECT
+  u REGEXP '[a-f0-9]{8}-[a-f0-9]{4}-4[a-f0-9]{3}-[89aAbB][a-f0-9]{3}-[a-f0-9]{12}' AS is_correct_version_and_revision,
+  COUNT(*)
+FROM t1 GROUP BY is_correct_version_and_revision;
+DROP TABLE t1;
+
+--echo #
+--echo # End of 11.6 tests
+--echo #
+
+SET debug_dbug="";

plugin/type_uuid/plugin.cc

-/* Copyright (c) 2019,2021, MariaDB Corporation
+/* Copyright (c) 2019,2024, MariaDB Corporation
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -16,7 +16,6 @@
 #define MYSQL_SERVER
 #include "mariadb.h"
 #include "sql_class.h"
-#include "sql_type_uuid.h"
 #include "item_uuidfunc.h"
 #include <mysql/plugin_data_type.h>
 #include <mysql/plugin_function.h>

plugin/type_uuid/sql_type_uuid.h

 #ifndef SQL_TYPE_UUID_INCLUDED
 #define SQL_TYPE_UUID_INCLUDED
 
-/* Copyright (c) 2019,2021 MariaDB Corporation
+/* Copyright (c) 2019,2024 MariaDB Corporation
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -331,23 +331,4 @@ typedef Type_handler_fbt<UUID<1>, Type_collection_uuid> Type_handler_uuid_old;
 typedef Type_handler_fbt<UUID<0>, Type_collection_uuid> Type_handler_uuid_new;
 
 
-class UUIDv1: public Type_handler_uuid_new::Fbt
-{
-public:
-  UUIDv1()
-  {
-    my_uuid((uchar*) m_buffer);
-  }
-  static bool construct_native(Native *to)
-  {
-    to->alloc(MY_UUID_SIZE);
-    to->length(MY_UUID_SIZE);
-    my_uuid((uchar*)to->ptr());
-    return 0;
-  }
-};
-
-#include "sql_type_uuid_v4.h"
-
-
 #endif // SQL_TYPE_UUID_INCLUDED

plugin/type_uuid/sql_type_uuid_v1.h

+#ifndef SQL_TYPE_UUID_V1_INCLUDED
+#define SQL_TYPE_UUID_V1_INCLUDED
+
+/* Copyright (c) 2024, MariaDB Corporation
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1335  USA */
+
+#include "sql_type_uuid.h"
+
+class UUIDv1: public Type_handler_uuid_new::Fbt
+{
+public:
+  UUIDv1()
+  {
+    my_uuid((uchar*) m_buffer);
+  }
+  static bool construct_native(Native *to)
+  {
+    to->alloc(MY_UUID_SIZE);
+    to->length(MY_UUID_SIZE);
+    my_uuid((uchar*)to->ptr());
+    return 0;
+  }
+};
+
+#endif // SQL_TYPE_UUID_V1_INCLUDED

plugin/type_uuid/sql_type_uuid_v4.h

@@ -35,28 +35,62 @@
   bits of random data.
 */
 
+#include "sql_type_uuid.h"
 #include "my_rnd.h"
 
-#define UUID_VERSION                         0x40
-#define UUID_VERSION_MASK                    0x0F
-#define UUID_VARIANT                         0x80
-#define UUID_VARIANT_MASK                    0x3F
+class UUIDv4: public Type_handler_uuid_new::Fbt
+{
+  static constexpr uchar UUID_VERSION()      { return 0x40; }
+  static constexpr uchar UUID_VERSION_MASK() { return 0x0F; }
+  static constexpr uchar UUID_VARIANT()      { return 0x80; }
+  static constexpr uchar UUID_VARIANT_MASK() { return 0x3F; }
 
-/**
-   Create a global unique identifier version 4 (uuidv4)
+  static void inject_version_and_variant(uchar *to)
+  {
+    to[6]= ((to[6] & UUID_VERSION_MASK()) | UUID_VERSION());
+    to[8]= ((to[8] & UUID_VARIANT_MASK()) | UUID_VARIANT());
+  }
 
-   @func  my_uuid_v4()
-   @param to   Store uuidv4 here. Must be of size MY_UUID_SIZE (16)
-   @return 1 in case of success and 0 in case of failure
-*/
-static inline bool my_uuid_v4(uchar *to)
-{
-  if (my_random_bytes(to, 16) != MY_AES_OK)
-      return 0;
+  // Construct using a my_rnd()-based fallback method
+  static void construct_fallback(char *to)
+  {
+    for (uint i= 0; i < 4; i++)
+      int4store(&to[i * 4], (uint32) (my_rnd(&sql_rand)*0xFFFFFFFF));
+  }
+
+  static void construct(char *to)
+  {
+    bool error= my_random_bytes((uchar*) to, 16) != MY_AES_OK;
+    DBUG_EXECUTE_IF("simulate_uuidv4_my_random_bytes_failure", error= true; );
+
+    if (error) // A very unlikely failure happened.
+    {
+      push_warning_printf(current_thd, Sql_condition::WARN_LEVEL_NOTE,
+                          ER_UNKNOWN_ERROR,
+                          "UUIDv4 generation failed; using a my_rnd fallback");
+      construct_fallback(to);
+    }
+    /*
+      We have random bytes at to[6] and to[8].
+      Let's inject proper version and variant to make it good UUIDv4.
+    */
+    inject_version_and_variant((uchar*) to);
+  }
+
+public:
+
+  UUIDv4()
+  {
+    construct(m_buffer);
+  }
+  static bool construct_native(Native *to)
+  {
+    to->alloc(MY_UUID_SIZE);
+    to->length(MY_UUID_SIZE);
+    construct((char*)to->ptr());
+    return 0;
+  }
 
-  to[6]= ((to[6] & UUID_VERSION_MASK) | UUID_VERSION);
-  to[8]= ((to[8] & UUID_VARIANT_MASK) | UUID_VARIANT);
-  return 1;
-}
+};
 
 #endif // SQL_TYPE_UUID_V4_INCLUDED