Follow-up to Bug #55582 which allows checking strings in if

  Simplified cases where a select was used to compare variable against ''

mysql-test/extra/rpl_tests/rpl_get_master_version_and_clock.test

@@ -34,7 +34,7 @@
 #
 
 connection slave;
-if (`SELECT $debug_sync_action = ''`)
+if (!$debug_sync_action)
 {
     --die Cannot continue. Please set value for debug_sync_action.
 }

mysql-test/extra/rpl_tests/rpl_loaddata.test

@@ -24,7 +24,7 @@ connection master;
 # MTR is not case-sensitive.
 let $lower_stmt_head= load data;
 let $UPPER_STMT_HEAD= LOAD DATA;
-if (`SELECT '$lock_option' <> ''`)
+if ($lock_option)
 {
   #if $lock_option is null, an extra blank is added into the statement,
   #this will change the result of rpl_loaddata test case. so $lock_option

mysql-test/include/check_concurrent_insert.inc

@@ -23,7 +23,7 @@
 # Reset DEBUG_SYNC facility for safety.
 set debug_sync= "RESET";
 
-if (`SELECT '$restore_table' <> ''`)
+if ($restore_table)
 {
 --eval create temporary table t_backup select * from $restore_table;
 }
@@ -82,7 +82,7 @@ connection default;
 
 --eval delete from $table where i = 0;
 
-if (`SELECT '$restore_table' <> ''`)
+if ($restore_table)
 {
 --eval truncate table $restore_table;
 --eval insert into $restore_table select * from t_backup;

mysql-test/include/check_no_concurrent_insert.inc

@@ -23,7 +23,7 @@
 # Reset DEBUG_SYNC facility for safety.
 set debug_sync= "RESET";
 
-if (`SELECT '$restore_table' <> ''`)
+if ($restore_table)
 {
 --eval create temporary table t_backup select * from $restore_table;
 }
@@ -67,7 +67,7 @@ if (!$success)
 
 --eval delete from $table where i = 0;
 
-if (`SELECT '$restore_table' <> ''`)
+if ($restore_table)
 {
 --eval truncate table $restore_table;
 --eval insert into $restore_table select * from t_backup;

mysql-test/include/get_relay_log_pos.inc

@@ -10,12 +10,12 @@
 #   # at this point, get_relay_log_pos.inc sets $relay_log_pos. echo position
 #   # in $relay_log_file: $relay_log_pos. 
 
-if (`SELECT '$relay_log_file' = ''`)
+if (!$relay_log_file)
 {
   --die 'variable $relay_log_file is null'
 }
 
-if (`SELECT '$master_log_pos' = ''`)
+if (!$master_log_pos)
 {
   --die 'variable $master_log_pos is null'
 }

mysql-test/include/kill_query.inc

@@ -44,7 +44,7 @@ connection master;
 # kill the query that is waiting
 eval kill query $connection_id;
 
-if (`SELECT '$debug_lock' != ''`)
+if ($debug_lock)
 {
   # release the lock to allow binlog continue
   eval SELECT RELEASE_LOCK($debug_lock);
@@ -57,7 +57,7 @@ reap;
 
 connection master;
 
-if (`SELECT '$debug_lock' != ''`)
+if ($debug_lock)
 {
   # get lock again to make the next query wait
   eval SELECT GET_LOCK($debug_lock, 10);

mysql-test/include/kill_query_and_diff_master_slave.inc

@@ -25,7 +25,7 @@ source include/kill_query.inc;
 connection master;
 disable_query_log;
 disable_result_log;
-if (`SELECT '$debug_lock' != ''`)
+if ($debug_lock)
 {
   eval SELECT RELEASE_LOCK($debug_lock);
 }
@@ -36,8 +36,8 @@ source include/diff_master_slave.inc;
 
 # Acquire the debug lock again if used
 connection master;
-disable_query_log; disable_result_log; if (`SELECT '$debug_lock' !=
-''`) { eval SELECT GET_LOCK($debug_lock, 10); } enable_result_log;
-enable_query_log;
+disable_query_log; disable_result_log;
+if ($debug_lock) { eval SELECT GET_LOCK($debug_lock, 10); }
+enable_result_log; enable_query_log;
 
 connection $connection_name;

mysql-test/include/setup_fake_relay_log.inc

@@ -56,7 +56,7 @@ if (`SELECT "$_sql_running" = "Yes" OR "$_io_running" = "Yes"`) {
 # Read server variables.
 let $MYSQLD_DATADIR= `SELECT @@datadir`;
 let $_fake_filename= query_get_value(SHOW VARIABLES LIKE 'relay_log', Value, 1);
-if (`SELECT '$_fake_filename' = ''`) {
+if (!$_fake_filename) {
   --echo Badly written test case: relay_log variable is empty. Please use the
   --echo server option --relay-log=FILE.
 }

mysql-test/include/show_binlog_events.inc

@@ -27,14 +27,14 @@ if (!$binlog_start)
 }
 
 --let $_statement=show binlog events
-if (`SELECT '$binlog_file' <> ''`)
+if ($binlog_file)
 {
   --let $_statement= $_statement in '$binlog_file'
 }
 
 --let $_statement= $_statement from $binlog_start
 
-if (`SELECT '$binlog_limit' <> ''`)
+if ($binlog_limit)
 {
   --let $_statement= $_statement limit $binlog_limit
 }

mysql-test/include/show_rpl_debug_info.inc

@@ -48,13 +48,13 @@ let $binlog_name= query_get_value("SHOW MASTER STATUS", File, 1);
 eval SHOW BINLOG EVENTS IN '$binlog_name';
 
 let $_master_con= $master_connection;
-if (`SELECT '$_master_con' = ''`)
+if (!$_master_con)
 {
   if (`SELECT '$_con' = 'slave'`)
   {
     let $_master_con= master;
   }
-  if (`SELECT '$_master_con' = ''`)
+  if (!$_master_con)
   {
     --echo Unable to determine master connection. No debug info printed for master.
     --echo Please fix the test case by setting $master_connection before sourcing
@@ -62,7 +62,7 @@ if (`SELECT '$_master_con' = ''`)
   }
 }
 
-if (`SELECT '$_master_con' != ''`)
+if ($_master_con)
 {
 
   let $master_binlog_name_io= query_get_value("SHOW SLAVE STATUS", Master_Log_File, 1);

mysql-test/include/wait_for_slave_io_error.inc

@@ -31,7 +31,7 @@
 # $master_connection
 #   See wait_for_slave_param.inc for description.
 
-if (`SELECT '$slave_io_errno' = ''`) {
+if (!$slave_io_errno) {
   --die !!!ERROR IN TEST: you must set \$slave_io_errno before sourcing wait_for_slave_io_error.inc
 }
 

mysql-test/include/wait_for_slave_param.inc

@@ -51,7 +51,7 @@ if (!$_slave_timeout_counter)
 }
 
 let $_slave_param_comparison= $slave_param_comparison;
-if (`SELECT '$_slave_param_comparison' = ''`)
+if (!$_slave_param_comparison)
 {
   let $_slave_param_comparison= =;
 }
@@ -71,7 +71,7 @@ while (`SELECT NOT('$_show_slave_status_value' $_slave_param_comparison '$slave_
 if (!$_slave_timeout_counter)
 {
   --echo **** ERROR: timeout after $slave_timeout seconds while waiting for slave parameter $slave_param $_slave_param_comparison $slave_param_value ****
-  if (`SELECT '$slave_error_message' != ''`)
+  if ($slave_error_message)
   {
     --echo Message: $slave_error_message
   }

mysql-test/include/wait_for_slave_sql_error.inc

@@ -24,7 +24,7 @@
 # $master_connection
 #   See wait_for_slave_param.inc for description.
 
-if (`SELECT '$slave_sql_errno' = ''`) {
+if (!$slave_sql_errno) {
   --die !!!ERROR IN TEST: you must set \$slave_sql_errno before sourcing wait_for_slave_sql_error.inc
 }
 

mysql-test/include/wait_for_status_var.inc

@@ -45,7 +45,7 @@ if (!$_status_timeout_counter)
 }
 
 let $_status_var_comparsion= $status_var_comparsion;
-if (`SELECT '$_status_var_comparsion' = ''`)
+if (!$_status_var_comparsion)
 {
   let $_status_var_comparsion= =;
 }

mysql-test/suite/rpl/t/rpl_killed_ddl.test

@@ -119,7 +119,7 @@ echo [on master];
 
 # This will block the execution of a statement at the DBUG_SYNC_POINT
 # with given lock name
-if (`SELECT '$debug_lock' != ''`)
+if ($debug_lock)
 {
   disable_query_log;
   disable_result_log;