How to Collect Large Optimizer Traces

Optimizer traces can be large for some queries.

In order to collect a large trace, you need to perform the following steps (using 128 MB as an example):

set global max_allowed_packet=128*1024*1024;

Reconnect specifying --max-allowed-packet=128000000 for the client as well.

set optimizer_trace=1;
set optimizer_trace_max_mem_size=127*1024*1024;

Now, one can run the query and save the large trace.

See Also

• optimizer_trace system variable
• optimizer_trace_max_mem_size system variable
• max_allowed_packet system variable