On Sat, Apr 11, 2015 at 11:03:22AM +0200, Roberto Cornacchia wrote:
> Hi there,
>
> I need a string tokenizer in MonetDB.
> The problem I have is not with the function itself, but with the fact
> that this is a 1 to N rows function.
>
> Implementing this for a single string value is easy enough, using a
> table function that takes a string a returns a table:
>
> create function tokenize(s string)
> returns table (token string)
> external name tokenize;
>
> select *
> from tokenize("one two three");
>
> That's fine.
> The issue I'm having is with extending this to a column of strings.
>
> Ideally, given a string column
>
> one two three
> four five six
> seven eight
>
> I'd like to get an output along these lines (simplistic representation
> here):
>
> one two three | one
> one two three | two
> one two three | three
> four five six | four
> four five six | five
> four five six | six
> seven eight   | seven
> seven eight   | eight
>
>
> I can sure code the c function and the mal wrapper to implement this,
> but I can't see how to map it to SQL, given that table functions don't
> accept identifiers as parameters. 
>
> Any idea? Any possible workaround?

In default you should be able to call tokenize on a column.
It will output the 'union' of all per row calls.
If you would like the 2 column output, you should take care of
this in your tokenize function, ie return both input and token.

Niels
> Thanks, Roberto
>

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--
Niels Nes, Manager ITF, Centrum Wiskunde & Informatica (CWI)
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