Function sql_support::debug_tools::define_debug_functions

pub fn define_debug_functions(c: &Connection) -> Result<()>

You can call this function to add all sql functions provided by this module to your connection. The list of supported functions is described below.

Note: you must enable the debug-tools feature for these functions to perform as described. If this feature is not enabled, functions of the same name will still exist, but will be no-ops.

dbg

dbg() is a simple sql function that prints all args to stderr and returns the last argument. It’s useful for instrumenting existing WHERE statements - eg, changing a statement

WHERE a.bar = foo

to

WHERE dbg("a bar", a.bar) = foo

will print the literal a bar followed by the value of a.bar, then return a.bar, so the semantics of the WHERE statement do not change. If you have a series of statements being executed (ie, statements separated by a ;), adding a new statement like SELECT dbg("hello"); is also possible.