canvas-lms/doc/trace_database_queries.md

Trace Database Queries

Canvas includes the "active_record_query_trace" gem when running in development or test mode. This gem prints a stack trace of every ActiveRecord query the Rails application makes.

The query trace logging is off by default, but can be enabled and configured by setting environment variables. Note that traces cannot be enabled in production mode.

Environment variable overview

ENV VAR	Description
AR_QUERY_TRACE	traces are enabled if this variable is set. Traces disabled otherwise.
AR_QUERY_TRACE_TYPE	Controls what kind of queries print traces. Valid values are "all", "write", and "read".
AR_QUERY_TRACE_LINES	Controls how many lines of the trace are printed. Defaults to 10.
AR_QUERY_TRACE_LEVEL	Filters the backtrace to "app", "rails", or "full"