debug

✅  tap a pipeline to emit debugging values

Synopsis

debug [ <expr> ] [ filter ( <pred> ) ]

Description

The debug operator passes its input unmodified to its output and for each value in the input, evaluates the optional expression <expr>, and transmits each result to a debugging output. If <expr> is omitted, then each input value is passed unmodified to the debugging output.

An optional filter may be applied to the values sent to the debugging output, which is specified with Boolean-valued expression <pred>. In this case, <pred> is applied to each input value of the debug operator and only the values for which <pred> is true are emitted as <expr> to the debugging output.

When running a query with the super command, the debugging output is printed to standard error. In this case, debugging output is displayed in the SUP format independent of the -f flag.

When running a query in a database service, the debugging output is transmitted to the client on the output channel named “debug”. If the client in this case is the super db command, then the debugging output is printed to standard error.

Note

A future version of SuperDB Desktop will support viewing debug output in a panel in the application.

Examples

Hello, world

# spq
values "hello, world" | debug {debug:this} | where false
# input

# expected output
{debug:"hello, world"}

Apply a filter to debug trace

# spq
values {x:1,y:2},{x:3,y:4} | debug y filter (x=1) | where false
# input

# expected output
2