MDEV-23327 Can't uninstall UDF if the implementation library file doesn't exist

Made cleanup of DROP (udf) FUNCTION procedure and also check of mysql.func (not only loaded udf).

mysql-test/r/udf.result

@@ -479,3 +479,17 @@ myfunc_int(max(a) over (order by b) , b)
 drop view v1;
 drop function myfunc_int;
 drop table t1;
+#
+# MDEV-23327: Can't uninstall UDF if the implementation library
+# file doesn't exist
+#
+insert into  mysql.func values ("unexisting_udf", 0, "soname", "function");
+select * from mysql.func WHERE name='unexisting_udf';
+name	ret	dl	type
+unexisting_udf	0	soname	function
+DROP FUNCTION unexisting_udf;
+select * from mysql.plugin WHERE name='unexisting_udf';
+name	dl
+DROP FUNCTION unexisting_udf;
+ERROR 42000: FUNCTION test.unexisting_udf does not exist
+# End of 10.2 tests

mysql-test/t/udf.test

@@ -541,3 +541,25 @@ select * from v1;
 drop view v1;
 drop function myfunc_int;
 drop table t1;
+
+--echo #
+--echo # MDEV-23327: Can't uninstall UDF if the implementation library
+--echo # file doesn't exist
+--echo #
+
+# emulate brocken so/ddl udf
+insert into  mysql.func values ("unexisting_udf", 0, "soname", "function");
+
+# check that we have the function "installed"
+select * from mysql.func WHERE name='unexisting_udf';
+
+# make attempt to drop the function
+DROP FUNCTION unexisting_udf;
+
+# check that we have the plugin uninstalled
+select * from mysql.plugin WHERE name='unexisting_udf';
+
+--error ER_SP_DOES_NOT_EXIST
+DROP FUNCTION unexisting_udf;
+
+--echo # End of 10.2 tests

sql/sql_parse.cc

@@ -5623,23 +5623,20 @@ mysql_execute_command(THD *thd)
           ! lex->spname->m_explicit_name)
       {
         /* DROP FUNCTION <non qualified name> */
-        udf_func *udf = find_udf(lex->spname->m_name.str,
-                                 lex->spname->m_name.length);
-        if (udf)
-        {
-          if (check_access(thd, DELETE_ACL, "mysql", NULL, NULL, 1, 0))
-            goto error;
-
-          if (!(res = mysql_drop_function(thd, &lex->spname->m_name)))
+        enum drop_udf_result rc= mysql_drop_function(thd,
+                                                     &lex->spname->m_name);
+        if (rc == UDF_DEL_RESULT_DELETED)
         {
           my_ok(thd);
           break;
         }
-          my_error(ER_SP_DROP_FAILED, MYF(0),
-                   "FUNCTION (UDF)", lex->spname->m_name.str);
+
+        if (rc == UDF_DEL_RESULT_ERROR)
           goto error;
-        }
 
+        DBUG_ASSERT(rc == UDF_DEL_RESULT_ABSENT);
+
+        // If there was no current database, so it can not be SP
         if (lex->spname->m_db.str == NULL)
         {
           if (lex->if_exists())

sql/sql_udf.cc

@@ -58,6 +58,8 @@ static udf_func *add_udf(LEX_STRING *name, Item_result ret,
                          char *dl, Item_udftype typ);
 static void del_udf(udf_func *udf);
 static void *find_udf_dl(const char *dl);
+static bool find_udf_everywhere(THD* thd, const char *name, uint len,
+                                TABLE *table);
 
 static char *init_syms(udf_func *tmp, char *nm)
 {
@@ -417,6 +419,45 @@ static udf_func *add_udf(LEX_STRING *name, Item_result ret, char *dl,
   return tmp;
 }
 
+/**
+  Find record with the udf in the udf func table
+
+  @param exact_name_str  udf name
+  @param exact_name_len  udf name length
+  @param table           table of mysql.func
+
+  @retval TRUE  found
+  @retral FALSE not found
+*/
+
+static bool find_udf_in_table(const char *exact_name_str, uint exact_name_len,
+                              TABLE *table)
+{
+  table->use_all_columns();
+  table->field[0]->store(exact_name_str, exact_name_len, &my_charset_bin);
+  return (!table->file->ha_index_read_idx_map(table->record[0], 0,
+                                              (uchar*) table->field[0]->ptr,
+                                              HA_WHOLE_KEY,
+                                              HA_READ_KEY_EXACT));
+}
+
+static bool remove_udf_in_table(const char *exact_name_str,
+                                uint exact_name_len,
+                                TABLE *table)
+{
+  if (find_udf_in_table(exact_name_str, exact_name_len, table))
+  {
+    int error;
+    if ((error= table->file->ha_delete_row(table->record[0])))
+    {
+      table->file->print_error(error, MYF(0));
+      return TRUE;
+    }
+  }
+  return FALSE;
+}
+
+
 /*
   Drop user defined function.
 
@@ -447,18 +488,21 @@ static int mysql_drop_function_internal(THD *thd, udf_func *udf, TABLE *table)
   if (!table)
     DBUG_RETURN(1);
 
-  table->use_all_columns();
-  table->field[0]->store(exact_name_str, exact_name_len, &my_charset_bin);
-  if (!table->file->ha_index_read_idx_map(table->record[0], 0,
-                                          (uchar*) table->field[0]->ptr,
-                                          HA_WHOLE_KEY,
-                                          HA_READ_KEY_EXACT))
-  {
-    int error;
-    if ((error= table->file->ha_delete_row(table->record[0])))
-      table->file->print_error(error, MYF(0));
-  }
-  DBUG_RETURN(0);
+  bool ret= remove_udf_in_table(exact_name_str, exact_name_len, table);
+  DBUG_RETURN(ret);
+}
+
+
+static TABLE *open_udf_func_table(THD *thd)
+{
+  TABLE_LIST tables;
+  TABLE *table;
+
+  tables.init_one_table(STRING_WITH_LEN("mysql"), STRING_WITH_LEN("func"),
+                        "func", TL_WRITE);
+  table= open_ltable(thd, &tables, TL_WRITE, MYSQL_LOCK_IGNORE_TIMEOUT);
+
+  return table;
 }
 
 
@@ -505,9 +549,7 @@ int mysql_create_function(THD *thd,udf_func *udf)
   if (check_ident_length(&udf->name))
     DBUG_RETURN(1);
 
-  tables.init_one_table(STRING_WITH_LEN("mysql"), STRING_WITH_LEN("func"),
-                        "func", TL_WRITE);
-  table= open_ltable(thd, &tables, TL_WRITE, MYSQL_LOCK_IGNORE_TIMEOUT);
+  table= open_udf_func_table(thd);
 
   mysql_rwlock_wrlock(&THR_LOCK_udf);
   DEBUG_SYNC(current_thd, "mysql_create_function_after_lock");
@@ -606,43 +648,59 @@ int mysql_create_function(THD *thd,udf_func *udf)
 }
 
 
-int mysql_drop_function(THD *thd,const LEX_STRING *udf_name)
+enum drop_udf_result mysql_drop_function(THD *thd, const LEX_STRING *udf_name)
 {
   TABLE *table;
-  TABLE_LIST tables;
   udf_func *udf;
   DBUG_ENTER("mysql_drop_function");
 
+  if (!(table= open_udf_func_table(thd)))
+    DBUG_RETURN(UDF_DEL_RESULT_ERROR);
+
+  // Fast pre-check
+  if (!mysql_rwlock_tryrdlock(&THR_LOCK_udf))
+  {
+    bool found=find_udf_everywhere(thd, udf_name->str, udf_name->length, table);
+    mysql_rwlock_unlock(&THR_LOCK_udf);
+    if (!found)
+    {
+      close_mysql_tables(thd);
+      DBUG_RETURN(UDF_DEL_RESULT_ABSENT);
+    }
+  }
+
   if (!initialized)
   {
+    close_mysql_tables(thd);
     if (opt_noacl)
-      my_error(ER_FUNCTION_NOT_DEFINED, MYF(0), udf_name->str);
-    else
-      my_message(ER_OUT_OF_RESOURCES, ER_THD(thd, ER_OUT_OF_RESOURCES),
-                 MYF(0));
-    DBUG_RETURN(1);
-  }
+      DBUG_RETURN(UDF_DEL_RESULT_ABSENT); // SP should be checked
 
-  tables.init_one_table(STRING_WITH_LEN("mysql"), STRING_WITH_LEN("func"),
-                        "func", TL_WRITE);
-  table= open_ltable(thd, &tables, TL_WRITE, MYSQL_LOCK_IGNORE_TIMEOUT);
+    my_message(ER_OUT_OF_RESOURCES, ER_THD(thd, ER_OUT_OF_RESOURCES), MYF(0));
+    DBUG_RETURN(UDF_DEL_RESULT_ERROR);
+  }
 
   mysql_rwlock_wrlock(&THR_LOCK_udf);
+
+  // re-check under protection
+  if (!find_udf_everywhere(thd, udf_name->str, udf_name->length, table))
+  {
+    close_mysql_tables(thd);
+    mysql_rwlock_unlock(&THR_LOCK_udf);
+    DBUG_RETURN(UDF_DEL_RESULT_ABSENT);
+  }
+
+  if (check_access(thd, DELETE_ACL, "mysql", NULL, NULL, 1, 0))
+    goto err;
+
+
   DEBUG_SYNC(current_thd, "mysql_drop_function_after_lock");
+
   if (!(udf= (udf_func*) my_hash_search(&udf_hash, (uchar*) udf_name->str,
                                         (uint) udf_name->length)) )
   {
-    if (thd->lex->check_exists)
-    {
-      push_warning_printf(thd, Sql_condition::WARN_LEVEL_NOTE,
-                          ER_FUNCTION_NOT_DEFINED,
-                          ER_THD(thd, ER_FUNCTION_NOT_DEFINED),
-                          udf_name->str);
-      goto done;
-    }
-
-    my_error(ER_FUNCTION_NOT_DEFINED, MYF(0), udf_name->str);
+    if (remove_udf_in_table(udf_name->str, (uint) udf_name->length, table))
       goto err;
+    goto done;
   }
 
   if (mysql_drop_function_internal(thd, udf, table))
@@ -656,13 +714,24 @@ int mysql_drop_function(THD *thd,const LEX_STRING *udf_name)
     while binlogging, to avoid binlog inconsistency.
   */
   if (write_bin_log(thd, TRUE, thd->query(), thd->query_length()))
-    DBUG_RETURN(1);
+    DBUG_RETURN(UDF_DEL_RESULT_ERROR);
 
-  DBUG_RETURN(0);
+  close_mysql_tables(thd);
+  DBUG_RETURN(UDF_DEL_RESULT_DELETED);
 
 err:
+  close_mysql_tables(thd);
   mysql_rwlock_unlock(&THR_LOCK_udf);
-  DBUG_RETURN(1);
+  DBUG_RETURN(UDF_DEL_RESULT_ERROR);
+}
+
+static bool find_udf_everywhere(THD* thd, const char *name, uint len,
+                                TABLE *table)
+{
+  if (initialized && my_hash_search(&udf_hash, (uchar*) name, len))
+    return true;
+
+  return find_udf_in_table(name, len, table);
 }
 
 #endif /* HAVE_DLOPEN */

sql/sql_udf.h

@@ -140,7 +140,13 @@ void udf_init(void),udf_free(void);
 udf_func *find_udf(const char *name, uint len=0,bool mark_used=0);
 void free_udf(udf_func *udf);
 int mysql_create_function(THD *thd,udf_func *udf);
-int mysql_drop_function(THD *thd,const LEX_STRING *name);
+enum drop_udf_result
+{
+  UDF_DEL_RESULT_ABSENT,
+  UDF_DEL_RESULT_DELETED,
+  UDF_DEL_RESULT_ERROR
+};
+enum drop_udf_result mysql_drop_function(THD *thd,const LEX_STRING *name);
 #else
 static inline void udf_init(void) { }
 static inline void udf_free(void) { }