Optimizer Debugging With GDB
You are viewing an old version of this article. View the current version here.
Some useful things for debugging optimizer code with gdb.
Printing the optimizer trace
Optimizer trace is collected as plain text. One can print the contents of the trace collected so far as follows:
printf "%s\n", thd->opt_trace->current_trace->current_json->output.str.Ptr
Printing current partial join prefix
best_access_path() is a function that adds another table to the join prefix.
When in or around that function, the following can be useful:
A macro to print the join prefix already constructed:
define bap_print_prefix set $i=0 while ($i < idx) p join->positions[$i++].table->table->alias.Ptr end end
Content reproduced on this site is the property of its respective owners, and this content is not reviewed in advance by MariaDB. The views, information and opinions expressed by this content do not necessarily represent those of MariaDB or any other party.