This bug could affect queries that had at least two references to a CTE that
used an embedded recursive CTE.
Starting from version 10.4 some code in With_element::clone_parsed_spec()
that assumed a certain order of selects after parsing the specification of
a CTE became not valid anymore. It could lead to global select lists where
some selects were missing. If a missing CTE happened to belong to the
recursive part of a recursive CTE some recursive table references were not
set as references to materialized derived tables and this caused a crash of
the server.
Approved by Oleksandr Byelkin <sanja@mariadb.com>
mark big_tables deprecated, the server can put temp tables on disk
as needed avoiding "table full" errors.
in case someone would really need to force a tmp table to be created
on disk from the start and for testing allow tmp_memory_table_size
to be set to 0.
fix tests to use that instead (and add a test that it actually
works).
make sure in-memory TREE size limit is never 0 (it's [ab]using
tmp_memory_table_size at the moment)
remove few sys_vars.*_basic tests
Forced columns of recursive CTEs to be nullable. SQL standard
requires this only from recursive columns, but in our code
so far we do not differentiate between recursive and non-recursive
columns when aggregating types of the union that specifies a
recursive CTE.
