No initialization of rpb's runtime flags causes problems with SKIP LOCKED when config ReadConsistency = 0 and SuperServer

[asfernandes]

This relates to comments in https://github.com/FirebirdSQL/firebird/pull/7350

Test case:

isql-1:

recreate table test(id int primary key, f01 int);

set term !;
create or alter procedure select_proc returns (o integer)
as
begin
    for select id from test rows 2 with lock skip locked into o do suspend;
end!
set term ;!

commit;
insert into test(id, f01) select row_number()over(), 0 from rdb$types rows 10;
commit;
update test set f01 = 1 where id in (1,5,9);
SQL> 

isql-2:

SQL> -- first time it works
SQL> rollback; set transaction read committed record_version NO wait; select * from select_proc;

SQL> -- second time it do not work
SQL> rollback; set transaction read committed record_version NO wait; select * from select_proc;
Statement failed, SQLSTATE = 40001
deadlock
-read conflicts with concurrent update
-concurrent transaction number is 107
-- Why error here ?

[asfernandes]

This no-initialization may cause others problems unrelated with SKIP LOCKED, but I'm not sure what exactly.

[pavel-zotov]

@@@ QA notes @@@ See test for #7350

[hvlad]

The fix is incomplete, try to select more records in select_proc, all 10 for example. Or try to update records with id's (1, 2) before call select_proc.

It looks like rpb_runtime_flags should be cleared before every fetch, not on execution start only.

[asfernandes]

I think you were wrong in reopening this bug as nature of cause seems completely unrelated. The original test case causes a problem of the loaded procedure metadata to share an uninitialized state.

What you are describing now happens even if the second session do not use the procedure.

[hvlad]

Ticket description not mentions 'procedure'. Both the issue and the committed fix is related with rpb_runtime_flags. This is why I reopened this ticket.

[asfernandes]

Another difference is that original issue do not happens in classic, and as stated, it may have others consequences (not deeply investigated) non-related with SKIP LOCKED.

The one you said also happens in classic.