MariaDB

  1. Bug #725050
  2. Comment #1

Comment 1 for bug 725050

Revision history for this message
Timour Katchaounov (timour) wrote : Re: Carsh with join_cache_hashed with semijoin and join_cache_level=3

The same example, but without setting a debug trace causes
a crash in 5.3-mwl89 in a different (but related) place, when
update_ref_and_keys is called for the first subquery
(counted from the outside->in). The call stack in 5.3-mwl89 is:

#0 add_key_field at sql_select.cc:3677
#1 add_key_fields at sql_select.cc:3981
#2 update_ref_and_keys at sql_select.cc:4332
#3 make_join_statistics at sql_select.cc:2955
#4 JOIN::optimize at sql_select.cc:952
#5 st_select_lex::optimize_unflattened_subqueries at sql_lex.cc:3140
#6 JOIN::optimize_unflattened_subqueries at opt_subselect.cc:3617
#7 JOIN::optimize at sql_select.cc:1447
#8 mysql_select

The reason for the difference is that 5.3-mwl89 optimizes subqueries
early during JOIN::optimize of the outer query.