- Let t/myisam_icp.test run include/icp_tests.inc with MRR/ICP turned ON (not OFF)

- Fix the compile-time-default value of optimizer_switch printed by mysqld --help --defaults

mysql-test/r/myisam_icp.result

+set @myisam_icp_tmp=@@optimizer_switch;
+set optimizer_switch='mrr=on,mrr_sort_keys=on,index_condition_pushdown=on';
 #
 # Bug#36981 - "innodb crash when selecting for update"
 #
@@ -221,8 +223,6 @@ FROM t3 JOIN t4 ON t4.f11 = t3.f10
 f11	f10
 DROP TABLE t1,t2,t3,t4;
 set optimizer_switch= @tmp_778434;
-set @myisam_icp_tmp=@@optimizer_switch;
-set optimizer_switch='mrr=on,mrr_sort_keys=on,index_condition_pushdown=on';
 drop table if exists t0, t1, t1i, t1m;
 #
 # BUG#826935 Assertion `!table || (!table->read_set || bitmap_is_set(table->read_set, field_index))' failed

mysql-test/t/myisam_icp.test

@@ -2,11 +2,11 @@
 # ICP/MyISAM tests (Index Condition Pushdown)
 #
 
---source include/icp_tests.inc
-
 set @myisam_icp_tmp=@@optimizer_switch;
 set optimizer_switch='mrr=on,mrr_sort_keys=on,index_condition_pushdown=on';
 
+--source include/icp_tests.inc
+
 --disable_warnings
 drop table if exists t0, t1, t1i, t1m;
 --enable_warnings

sql/mysqld.cc

@@ -481,7 +481,7 @@ static const char *optimizer_switch_str="index_merge=on,index_merge_union=on,"
                                         "index_merge_sort_union=on,"
                                         "index_merge_intersection=on,"
                                         "index_merge_sort_intersection=off,"
-                                        "index_condition_pushdown=on,"
+                                        "index_condition_pushdown=off,"
                                         "derived_merge=off,"
                                         "derived_with_keys=off,"
                                         "firstmatch=off,"