Re: tab-completion debug print

Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> writes:
> I was reminded that I was often annoyed with identifying the code
> that made a word-completion, by hearing the same complaint from a
> collegue of mine just now.
> Something like the attached that tweaks completion_matches calls
> lets psql emit the line number where a word-completion
> happens. The output can be split out using redirection so that it
> doesn't break into the conversation on console.

> (make -s COPT=-DTABCOMPLETION_DEBUG install)
> $ psql postgres 2>~debug.out
> =# alt[tab]er [tab]t[tab]ab[tab] [tab]

> You can see the following output in another bash session.
> $ tail -f ~/debug.out
> [1414][1435][1435][1435][1431]
> Every number enclosed by brackets is the line number in
> tab-complete.c, where completion happens.

> Is this useful? Any suggestions, thoughts?

Hm. I can see the value of instrumenting tab-complete when you're trying
to debug why it did something, but this output format seems pretty terse
and unreadable. Can we get it to print the completion text as well?
I'm imagining something more like

1414: "er "
1435: ""
1435: "ab"
1435: ""
1431: ""

Perhaps there's room as well to print the context that the match looked
at:

1414: "alt" -> "er "
1435: "alter " -> ""
1435: "alter t" -> "ab"

etc.

regards, tom lane