MDEV-19455: Avoid SET DEBUG_DBUG='-d,...' construct

Apply the correct pattern for debug instrumentation:

SET @save_dbug=@@debug_dbug;
SET debug_dbug='+d,...';
...
SET debug_dbug=@save_dbug;

Numerous tests use statements of the form

SET debug_dbug='-d,...';

which will inadvertently enable all DBUG tracing output,
causing unnecessary waste of resources.

4 files changed, 10 insertions, 14 deletions

diff --git a/mysql-test/t/drop_bad_db_type.test b/mysql-test/t/drop_bad_db_type.test
index 69e1a889b18..117501f0a49 100644
--- a/mysql-test/t/drop_bad_db_type.test
+++ b/mysql-test/t/drop_bad_db_type.test
@@ -7,6 +7,7 @@ if (!$HA_ARCHIVE_SO) {
 
 let $mysqld_datadir= `select @@datadir`;
 
+SET @save_dbug = @@debug_dbug;
 set debug_dbug='+d,unstable_db_type';
 
 install soname 'ha_archive';
@@ -21,5 +22,4 @@ drop table t1;
 --list_files $mysqld_datadir/test
 uninstall soname 'ha_archive';
 
-set debug_dbug='-d,unstable_db_type';
-
+set debug_dbug=@save_dbug;
diff --git a/mysql-test/t/drop_debug.test b/mysql-test/t/drop_debug.test
index 21069b57285..4ba16f1cc20 100644
--- a/mysql-test/t/drop_debug.test
+++ b/mysql-test/t/drop_debug.test
@@ -10,17 +10,13 @@
 --echo # --
 --echo
 
---disable_warnings
-DROP DATABASE IF EXISTS mysql_test;
---enable_warnings
-
---echo
 CREATE DATABASE mysql_test;
 CREATE TABLE mysql_test.t1(a INT);
 CREATE TABLE mysql_test.t2(b INT);
 CREATE TABLE mysql_test.t3(c INT);
 
 --echo
+SET @save_dbug = @@debug_dbug;
 SET SESSION debug_dbug= "+d,bug43138";
 
 --echo
@@ -28,7 +24,7 @@ SET SESSION debug_dbug= "+d,bug43138";
 DROP DATABASE mysql_test;
 
 --echo
-SET SESSION debug_dbug= "-d,bug43138";
+SET SESSION debug_dbug=@save_dbug;
 
 --echo
 --echo # --
diff --git a/mysql-test/t/partition_debug_sync.test b/mysql-test/t/partition_debug_sync.test
index 027a4bd19a7..df4901ab78f 100644
--- a/mysql-test/t/partition_debug_sync.test
+++ b/mysql-test/t/partition_debug_sync.test
@@ -6,10 +6,7 @@
 --source include/have_partition.inc
 --source include/have_debug_sync.inc
 
---disable_warnings
-DROP TABLE IF EXISTS t1, t2;
 SET DEBUG_SYNC= 'RESET';
---enable_warnings
 
 --echo #
 --echo # Bug#42438: Crash ha_partition::change_table_ptr
@@ -30,6 +27,7 @@ ENGINE = MYISAM
  PARTITION p1 VALUES LESS THAN (20),
  PARTITION p2 VALUES LESS THAN (100),
  PARTITION p3 VALUES LESS THAN MAXVALUE ) */;
+SET @save_dbug=@@debug_dbug;
 SET SESSION debug_dbug= "+d,sleep_before_create_table_no_lock";
 SET DEBUG_SYNC= 'alter_table_before_create_table_no_lock SIGNAL removing_partitioning WAIT_FOR waiting_for_alter';
 SET DEBUG_SYNC= 'alter_table_before_main_binlog SIGNAL partitioning_removed';
@@ -43,7 +41,7 @@ DROP TABLE IF EXISTS t1;
 --echo # Con 1
 connection con1;
 --reap
-SET SESSION debug_dbug= "-d,sleep_before_create_table_no_lock";
+SET SESSION debug_dbug=@save_dbug;
 connection default;
 SET DEBUG_SYNC= 'RESET';
 connection con1;
@@ -70,12 +68,13 @@ SET DEBUG_SYNC= 'alter_table_before_rename_result_table WAIT_FOR delete_done';
 --send ALTER TABLE t2 REMOVE PARTITIONING
 connection default;
 --echo # Con default
+SET @save_dbug=@@debug_dbug;
 SET SESSION debug_dbug= "+d,sleep_before_no_locks_delete_table";
 SET DEBUG_SYNC= 'now WAIT_FOR removing_partitions';
 SET DEBUG_SYNC= 'rm_table_no_locks_before_delete_table SIGNAL waiting_for_alter';
 SET DEBUG_SYNC= 'rm_table_no_locks_before_binlog SIGNAL delete_done';
 DROP TABLE IF EXISTS t2;
-SET SESSION debug_dbug= "-d,sleep_before_no_locks_delete_table";
+SET SESSION debug_dbug=@save_dbug;
 --echo # Con 1
 connection con1;
 --error ER_NO_SUCH_TABLE
diff --git a/mysql-test/t/sp-code.test b/mysql-test/t/sp-code.test
index d4b63a73920..129a68204ba 100644
--- a/mysql-test/t/sp-code.test
+++ b/mysql-test/t/sp-code.test
@@ -696,9 +696,10 @@ END|
 
 delimiter ;|
 
+SET @save_dbug = @@debug_dbug;
 SET SESSION debug_dbug="+d,bug23032_emit_warning";
 CALL p1();
-SET SESSION debug_dbug="-d,bug23032_emit_warning";
+SET SESSION debug_dbug=@save_dbug;
 
 DROP PROCEDURE p1;
 DROP TABLE t1;