MDEV-18855 Mariabackup should fetch innodb_compression_level from running server

- Fetch innodb_compression_level from the running server.Add the value
of innodb_compression_level in backup-my.cnf file during backup phase.
So that prepare can use the innodb_compression_level variable from
backup-my.cnf

extra/mariabackup/backup_mysql.cc

@@ -54,7 +54,7 @@ Place, Suite 330, Boston, MA 02111-1307 USA
 #include "mysqld.h"
 #include "encryption_plugin.h"
 #include <sstream>
-
+#include "page0zip.h"
 
 char *tool_name;
 char tool_args[2048];
@@ -350,6 +350,7 @@ get_mysql_vars(MYSQL *connection)
 	char *innodb_undo_directory_var = NULL;
 	char *innodb_page_size_var = NULL;
 	char *innodb_undo_tablespaces_var = NULL;
+	char *page_zip_level_var = NULL;
 	char *endptr;
 	unsigned long server_version = mysql_get_server_version(connection);
 
@@ -379,6 +380,7 @@ get_mysql_vars(MYSQL *connection)
 		{"innodb_undo_directory", &innodb_undo_directory_var},
 		{"innodb_page_size", &innodb_page_size_var},
 		{"innodb_undo_tablespaces", &innodb_undo_tablespaces_var},
+		{"innodb_compression_level", &page_zip_level_var},
 		{NULL, NULL}
 	};
 
@@ -512,7 +514,13 @@ get_mysql_vars(MYSQL *connection)
 	}
 
 	if (innodb_undo_tablespaces_var) {
-		srv_undo_tablespaces = strtoul(innodb_undo_tablespaces_var, &endptr, 10);
+		srv_undo_tablespaces = strtoul(innodb_undo_tablespaces_var,
+					       &endptr, 10);
+		ut_ad(*endptr == 0);
+	}
+
+	if (page_zip_level_var != NULL) {
+		page_zip_level = strtoul(page_zip_level_var, &endptr, 10);
 		ut_ad(*endptr == 0);
 	}
 
@@ -1574,6 +1582,7 @@ bool write_backup_config_file()
 		"innodb_log_block_size=%lu\n"
 		"innodb_undo_directory=%s\n"
 		"innodb_undo_tablespaces=%lu\n"
+		"innodb_compression_level=%u\n"
 		"%s%s\n"
 		"%s%s\n"
 		"%s\n",
@@ -1586,6 +1595,7 @@ bool write_backup_config_file()
 		srv_log_block_size,
 		srv_undo_dir,
 		srv_undo_tablespaces,
+		page_zip_level,
 		innobase_doublewrite_file ? "innodb_doublewrite_file=" : "",
 		innobase_doublewrite_file ? innobase_doublewrite_file : "",
 		innobase_buffer_pool_filename ?

extra/mariabackup/xtrabackup.cc

@@ -597,7 +597,8 @@ enum options_xtrabackup
 
   OPT_XTRA_TABLES_EXCLUDE,
   OPT_XTRA_DATABASES_EXCLUDE,
-  OPT_PROTOCOL
+  OPT_PROTOCOL,
+  OPT_INNODB_COMPRESSION_LEVEL
 };
 
 struct my_option xb_client_options[] =
@@ -1145,6 +1146,11 @@ Disable with --skip-innodb-doublewrite.", (G_PTR*) &innobase_use_doublewrite,
    (G_PTR*)&srv_undo_tablespaces, (G_PTR*)&srv_undo_tablespaces,
    0, GET_ULONG, REQUIRED_ARG, 0, 0, 126, 0, 1, 0},
 
+  {"innodb_compression_level", OPT_INNODB_COMPRESSION_LEVEL,
+   "Compression level used for zlib compression.",
+   (G_PTR*)&page_zip_level, (G_PTR*)&page_zip_level,
+   0, GET_UINT, REQUIRED_ARG, 6, 0, 9, 0, 0, 0},
+
   {"defaults_group", OPT_DEFAULTS_GROUP, "defaults group in config file (default \"mysqld\").",
    (G_PTR*) &defaults_group, (G_PTR*) &defaults_group,
    0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
@@ -1381,6 +1387,10 @@ xb_get_one_option(int optid,
     ADD_PRINT_PARAM_OPT(innodb_checksum_algorithm_names[srv_log_checksum_algorithm]);
     break;
 
+  case OPT_INNODB_COMPRESSION_LEVEL:
+    ADD_PRINT_PARAM_OPT(page_zip_level);
+    break;
+
   case OPT_INNODB_BUFFER_POOL_FILENAME:
 
     ADD_PRINT_PARAM_OPT(innobase_buffer_pool_filename);

mysql-test/suite/mariabackup/page_compression_level.result

+set global innodb_compression_level = 3;
+CREATE TABLE t1(c1 INT, b CHAR(20)) ENGINE=INNODB PAGE_COMPRESSED=1;
+INSERT INTO t1 VALUES(1, 'mariadb');
+# xtrabackup backup
+# xtrabackup prepare
+FOUND /innodb_compression_level=3/ in backup-my.cnf
+DELETE FROM t1;
+ALTER TABLE t1 DISCARD TABLESPACE;
+ALTER TABLE t1 IMPORT TABLESPACE;
+SELECT * FROM t1;
+c1	b
+1	mariadb
+DROP TABLE t1;
+set global innodb_compression_level = default;

mysql-test/suite/mariabackup/page_compression_level.test

+#--source include/innodb_page_size.inc
+
+set global innodb_compression_level = 3;
+CREATE TABLE t1(c1 INT, b CHAR(20)) ENGINE=INNODB PAGE_COMPRESSED=1;
+INSERT INTO t1 VALUES(1, 'mariadb');
+
+echo # xtrabackup backup;
+let $targetdir=$MYSQLTEST_VARDIR/tmp/backup;
+
+--disable_result_log
+exec $XTRABACKUP --defaults-file=$MYSQLTEST_VARDIR/my.cnf  --backup --target-dir=$targetdir;
+echo # xtrabackup prepare;
+exec $XTRABACKUP --defaults-file=$MYSQLTEST_VARDIR/my.cnf --defaults-group-suffix=.1 --prepare --export --target-dir=$targetdir;
+--enable_result_log
+
+--let SEARCH_PATTERN=innodb_compression_level=3
+--let SEARCH_FILE=$targetdir/backup-my.cnf
+--source include/search_pattern_in_file.inc
+
+DELETE FROM t1;
+ALTER TABLE t1 DISCARD TABLESPACE;
+let $MYSQLD_DATADIR= `select @@datadir`;
+copy_file $targetdir/test/t1.ibd $MYSQLD_DATADIR/test/t1.ibd;
+copy_file $targetdir/test/t1.cfg $MYSQLD_DATADIR/test/t1.cfg;
+ALTER TABLE t1 IMPORT TABLESPACE;
+
+SELECT * FROM t1;
+
+DROP TABLE t1;
+set global innodb_compression_level = default;
+rmdir $targetdir;