MDEV-23335 MariaBackup Incremental Does Not Reflect Dropped/Created Databases

extra/mariabackup/backup_copy.cc

@@ -57,6 +57,9 @@ Street, Fifth Floor, Boston, MA 02110-1335 USA
 #include "backup_copy.h"
 #include "backup_mysql.h"
 #include <btr0btr.h>
+#ifdef _WIN32
+#include <direct.h> /* rmdir */
+#endif
 
 #define ROCKSDB_BACKUP_DIR "#rocksdb"
 
@@ -1623,7 +1626,49 @@ bool backup_finish()
 	return(true);
 }
 
-bool
+
+/*
+  Drop all empty database directories in the base backup
+  that do not exists in the icremental backup.
+
+  This effectively re-plays all DROP DATABASE statements happened
+  in between base backup and incremental backup creation time.
+
+  Note, only checking if base_dir/db/ is empty is not enough,
+  because inc_dir/db/db.opt might have been dropped for some reasons,
+  which may also result into empty base_dir/db/.
+
+  Only the fact that at the same time:
+  - base_dir/db/ exists
+  - inc_dir/db/ does not exist
+  means that DROP DATABASE happened.
+*/
+static void
+ibx_incremental_drop_databases(const char *base_dir,
+                               const char *inc_dir)
+{
+	datadir_node_t node;
+	datadir_node_init(&node);
+	datadir_iter_t *it = datadir_iter_new(base_dir);
+
+	while (datadir_iter_next(it, &node)) {
+		if (node.is_empty_dir) {
+			char path[FN_REFLEN];
+			snprintf(path, sizeof(path), "%s/%s",
+				 inc_dir, node.filepath_rel);
+			if (!directory_exists(path, false)) {
+				msg("Removing %s", node.filepath);
+				rmdir(node.filepath);
+			}
+		}
+
+	}
+	datadir_iter_free(it);
+	datadir_node_free(&node);
+}
+
+
+static bool
 ibx_copy_incremental_over_full()
 {
 	const char *ext_list[] = {"frm", "isl", "MYD", "MYI", "MAD", "MAI",
@@ -1706,6 +1751,8 @@ ibx_copy_incremental_over_full()
 			}
 			copy_or_move_dir(path, ROCKSDB_BACKUP_DIR, true, true);
 		}
+		ibx_incremental_drop_databases(xtrabackup_target_dir,
+					       xtrabackup_incremental_dir);
 	}
 
 

mysql-test/suite/mariabackup/incremental_drop_db.result

@@ -0,0 +1,30 @@
+call mtr.add_suppression("InnoDB: New log files created");
+#
+# Start of 10.3 tests
+#
+#
+# MDEV-23335 MariaBackup Incremental Does Not Reflect Dropped/Created Databases
+#
+CREATE DATABASE db1;
+CREATE DATABASE db2;
+CREATE TABLE db1.t1 (a INT) ENGINE=MyISAM;
+CREATE TABLE db1.t2 (a INT) ENGINE=InnoDB;
+# Create base backup
+DROP DATABASE db1;
+# Create incremental backup
+# Remove incremental_dir/db2/db.opt file to make incremental_dir/db2/ empty
+# Prepare base backup, apply incremental one
+# shutdown server
+# remove datadir
+# xtrabackup move back
+# restart server
+# Expect no 'db1' in the output, because it was really dropped.
+# Expect 'db2' in the ouput, because it was not dropped!
+# (its incremental directory was emptied only)
+SHOW DATABASES LIKE 'db%';
+Database (db%)
+db2
+DROP DATABASE db2;
+#
+# End of 10.3 tests
+#

mysql-test/suite/mariabackup/incremental_drop_db.test

@@ -0,0 +1,68 @@
+--source include/have_innodb.inc
+call mtr.add_suppression("InnoDB: New log files created");
+
+--echo #
+--echo # Start of 10.3 tests
+--echo #
+
+--echo #
+--echo # MDEV-23335 MariaBackup Incremental Does Not Reflect Dropped/Created Databases
+--echo #
+
+--let $datadir=`SELECT @@datadir`
+--let $basedir=$MYSQLTEST_VARDIR/tmp/backup
+--let $incremental_dir=$MYSQLTEST_VARDIR/tmp/backup_inc1
+
+# Create two databases:
+# - db1 is dropped normally below
+# - db2 is used to cover a corner case: its db.opt file is removed
+
+# Incremental backup contains:
+# - no directory for db1
+# - an empty directory for db2 (after we remove db2/db.opt)
+
+
+CREATE DATABASE db1;
+CREATE DATABASE db2;
+
+# Add some tables to db1
+CREATE TABLE db1.t1 (a INT) ENGINE=MyISAM;
+CREATE TABLE db1.t2 (a INT) ENGINE=InnoDB;
+
+--echo # Create base backup
+--disable_result_log
+--exec $XTRABACKUP --defaults-file=$MYSQLTEST_VARDIR/my.cnf --backup --target-dir=$basedir
+--enable_result_log
+
+DROP DATABASE db1;
+
+--echo # Create incremental backup
+--exec $XTRABACKUP --defaults-file=$MYSQLTEST_VARDIR/my.cnf --backup --target-dir=$incremental_dir --incremental-basedir=$basedir
+
+--echo # Remove incremental_dir/db2/db.opt file to make incremental_dir/db2/ empty
+--remove_file $incremental_dir/db2/db.opt
+
+
+--echo # Prepare base backup, apply incremental one
+--disable_result_log
+--exec $XTRABACKUP --prepare --target-dir=$basedir
+--exec $XTRABACKUP --prepare --target-dir=$basedir --incremental-dir=$incremental_dir
+--enable_result_log
+
+--let $targetdir=$basedir
+--source include/restart_and_restore.inc
+--enable_result_log
+
+--echo # Expect no 'db1' in the output, because it was really dropped.
+--echo # Expect 'db2' in the ouput, because it was not dropped!
+--echo # (its incremental directory was emptied only)
+
+SHOW DATABASES LIKE 'db%';
+DROP DATABASE db2;
+
+--rmdir $basedir
+--rmdir $incremental_dir
+
+--echo #
+--echo # End of 10.3 tests
+--echo #