MDEV-19347: Mariabackup does not honor ignore_db_dirs from server

config.

The solution is to read the system variable value on startup and to fill
databases_exclude_hash.

xb_load_list_string() became non-static and was reformatted. The system
variable value is read and processed in get_mysql_vars(), which was also
reformatted.

extra/mariabackup/xtrabackup.cc

@@ -3632,6 +3632,11 @@ xb_register_exclude_filter_entry(
 				 &tables_exclude_hash);
 }
 
+void register_ignore_db_dirs_filter(const char *name)
+{
+  xb_add_filter(name, &databases_exclude_hash);
+}
+
 /***********************************************************************
 Register new table for the filter.  */
 static
@@ -3694,26 +3699,24 @@ xb_register_exclude_regex(
 
 typedef void (*insert_entry_func_t)(const char*);
 
-/***********************************************************************
-Scan string and load filter entries from it.  */
-static
-void
-xb_load_list_string(
-/*================*/
-	char* list,			/*!< in: string representing a list */
-	const char* delimiters,		/*!< in: delimiters of entries */
-	insert_entry_func_t ins)	/*!< in: callback to add entry */
+/* Scan string and load filter entries from it.
+@param[in] list string representing a list
+@param[in] delimiters delimiters of entries
+@param[in] ins callback to add entry */
+void xb_load_list_string(char *list, const char *delimiters,
+                         insert_entry_func_t ins)
 {
-	char*	p;
-	char*	saveptr;
+  char *p;
+  char *saveptr;
 
-	p = strtok_r(list, delimiters, &saveptr);
-	while (p) {
+  p= strtok_r(list, delimiters, &saveptr);
+  while (p)
+  {
 
-		ins(p);
+    ins(p);
 
-		p = strtok_r(NULL, delimiters, &saveptr);
-	}
+    p= strtok_r(NULL, delimiters, &saveptr);
+  }
 }
 
 /***********************************************************************

extra/mariabackup/xtrabackup.h

@@ -194,4 +194,14 @@ void mdl_lock_init();
 void mdl_lock_table(ulint space_id);
 void mdl_unlock_all();
 bool ends_with(const char *str, const char *suffix);
+
+typedef void (*insert_entry_func_t)(const char*);
+
+/* Scan string and load filter entries from it.
+@param[in] list string representing a list
+@param[in] delimiters delimiters of entries
+@param[in] ins callback to add entry */
+void xb_load_list_string(char *list, const char *delimiters,
+                         insert_entry_func_t ins);
+void register_ignore_db_dirs_filter(const char *name);
 #endif /* XB_XTRABACKUP_H */

mysql-test/suite/mariabackup/partial_exclude.opt

+--ignore-db-dirs=db3
+--ignore-db-dirs=db4

mysql-test/suite/mariabackup/partial_exclude.result

+select @@ignore_db_dirs;
+@@ignore_db_dirs
+db3,db4
 CREATE TABLE t1(i INT) ENGINE INNODB;
 INSERT INTO t1 VALUES(1);
 CREATE TABLE t2(i int) ENGINE INNODB;

mysql-test/suite/mariabackup/partial_exclude.test

 #--source include/innodb_page_size.inc
 
 # Test --databases-exclude and --tables-exclude feature of xtrabackup 2.3.8
+select @@ignore_db_dirs;
+
+let $MYSQLD_DATADIR= `select @@datadir`;
+
+mkdir $MYSQLD_DATADIR/db3;
+mkdir $MYSQLD_DATADIR/db4;
+mkdir $MYSQLD_DATADIR/db5;
 
 CREATE TABLE t1(i INT) ENGINE INNODB;
 INSERT INTO t1 VALUES(1);
@@ -24,8 +31,19 @@ list_files $targetdir/test *.ibd;
 # check that db2 database is not in the backup (excluded)
 --error 1
 list_files $targetdir/db2 *.ibd;
+# check that db3 database is not in the backup (excluded)
+--error 1
+list_files $targetdir/db3 *.ibd;
+# check that db4 database is not in the backup (excluded)
+--error 1
+list_files $targetdir/db4 *.ibd;
+# check that db5 database is in the backup
+list_files $targetdir/db5 *.ibd;
 
 DROP TABLE t1;
 DROP TABLE t2;
 DROP DATABASE db2;
+rmdir $MYSQLD_DATADIR/db3;
+rmdir $MYSQLD_DATADIR/db4;
+rmdir $MYSQLD_DATADIR/db5;
 rmdir $targetdir;