Re: Making tab-complete.c easier to maintain

Hello, I tried to implement the mini-language, which is a
simplified reglar expression for this specific use.

As a ultra-POC, the attached patch has very ad-hoc preprocess
function and does on-the-fly preprocessing, compilation then
execution of regular expression. And it is applied to only the
first ten or so matchings in psql_completion().

The first attachment is the same with that of previous patchset.

Every matching line looks like the following,

> else if (RM("ALTER {AGGREGATE|FUNCTION} [#id](.."))
>     COMPLETE_WITH_FUNCTION_ARG(CAPTURE(1));

As a temporary desin, "{}" means grouping, "|" means alternatives,
"[]" means capture and '#id' means any identifier.

The largest problem of this would be its computation cost:( This
in turn might be too slow if about three hundred matches run...

I see no straight-forward way to preprocess these strings.. A
possible solution would be extracting these strings then
auto-generate a c-srouce to preprocess them. And when running,
RM() retrieves the compiled regular expression using the string
as the key.


At Tue, 17 Nov 2015 15:35:43 +0900 (Tokyo Standard Time), Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp> wrote in
<20151117.153543.183036803.horiguchi.kyotaro@lab.ntt.co.jp>
> At Mon, 16 Nov 2015 12:16:07 -0300, Alvaro Herrera <alvherre@2ndquadrant.com> wrote in
<20151116151606.GW614468@alvherre.pgsql>
> > I don't think this is an improvement.  It seems to me that a lot more
> > work is required to maintain these regular expressions, which while
> > straightforward are not entirely trivial (harder to read).
> > 
> > If we could come up with a reasonable format that is pre-processed to a
> > regexp, that might be better.  I think Thomas' proposed patch is closer
> > to that than Horiguchi-san's.
> 
> I aimed that matching mechanism can handle optional elements in
> syntexes more robustly. But as all you are saying, bare regular
> expression is too complex here.

At Tue, 17 Nov 2015 16:09:25 +0900 (Tokyo Standard Time), Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp> wrote in
<20151117.160925.45883793.horiguchi.kyotaro@lab.ntt.co.jp>
> if (Match("^,ALTER,TABLE,\id,$") ||
>     Match("^,ALTER,TABLE,IF,EXISTS,\id,$"))...
> 
> Interpreting this kind of mini-language into regular expressions
> could be doable..

regards,

-- 
Kyotaro Horiguchi
NTT Open Source Software Center