get_key_scans_params: Conditional jump or move depends on uninitialised value

create table t1 (pk int, i int, v int, primary key (pk), key(v)) engine=myisam;

insert into t1 (pk,i,v) values (1,1,2),(2,2,4),(3,3,6),(4,4,8),(5,5,10),(6,6,12),(7,7,14),(8,8,16);

create table t2 (a int, b int) engine=myisam;

insert into t2 values (1,2),(2,4);

select * from t1 inner join t2 on ( t2.b = t1.v or t2.a = t1.pk );

drop table t1, t2;

==14854== Thread 4:

==14854== Conditional jump or move depends on uninitialised value(s)

==14854==    at 0x7B067B: get_key_scans_params(PARAM*, SEL_TREE*, bool, bool, double) (opt_range.cc:6805)

==14854==    by 0x7AB9F2: get_best_disjunct_quick(PARAM*, SEL_IMERGE*, double) (opt_range.cc:4711)

==14854==    by 0x7A901D: SQL_SELECT::test_quick_select(THD*, Bitmap<64u>, unsigned long long, unsigned long long, bool, bool) (opt_range.cc:3212)

==14854==    by 0x5301C6: make_join_select(JOIN*, SQL_SELECT*, Item*) (sql_select.cc:9145)

==14854==    by 0x51981C: JOIN::optimize() (sql_select.cc:1460)

==14854==    by 0x51F68E: mysql_select(THD*, Item***, TABLE_LIST*, unsigned int, List<Item>&, Item*, unsigned int, st_order*, st_order*, Item*, st_order*, unsigned long long, select_result*, st_select_lex_unit*, st_select_lex*) (sql_select.cc:3121)

==14854==    by 0x515B6D: handle_select(THD*, LEX*, select_result*, unsigned long) (sql_select.cc:312)

==14854==    by 0x4ED5D1: execute_sqlcom_select(THD*, TABLE_LIST*) (sql_parse.cc:4684)

==14854==    by 0x4E64D2: mysql_execute_command(THD*) (sql_parse.cc:2222)

==14854==    by 0x4F01B2: mysql_parse(THD*, char*, unsigned int, Parser_state*) (sql_parse.cc:5929)

==14854==    by 0x4E3A50: dispatch_command(enum_server_command, THD*, char*, unsigned int) (sql_parse.cc:1067)

==14854==    by 0x4E2C60: do_command(THD*) (sql_parse.cc:793)

==14854==    by 0x5EE7F4: do_handle_one_connection(THD*) (sql_connect.cc:1268)

==14854==    by 0x5EE563: handle_one_connection (sql_connect.cc:1184)

==14854==    by 0x997777: pfs_spawn_thread (pfs.cc:1015)

==14854==    by 0x4E3F4A3: start_thread (pthread_create.c:456)

commit 5af12e463549e4bbc2ce6ab720d78937d5e5db4e

Author: Igor Babaev

Date:   Thu Mar 12 23:50:20 2020 -0700

    MDEV-21932 A fast plan with ROR index-merge is ignored when

              'index_merge_sort_union=off'