Re: why non-greedy modifier for one atom changesgreediness of other atoms?

hubert depesz lubaczewski wrote:
>> Example:
>> # select x, substring( x from E'^((.*?)(\\.[0-9]+))') from 
>( values ('ab.123xxx.46hfd'),('a.b.c.d.123xx')) as q (x);
>>         x        | substring
>> -----------------+-----------
>>  ab.123xxx.46hfd | ab.1
>>  a.b.c.d.123xx   | a.b.c.d.1
>> (2 rows)
>> 
>> 
>> I found in docs, that this is what happens, but I don't understand the
>> logic behind forcing unique greediness in whole expression.

Yes, that's odd.

>> Also - how can one write a regexp that will match "ab.123" and
>> "a.b.c.d.123" respectively?
> 
> 
> sorry - it could have be unclear - in case of string 'ab123bc.12xx'
> return value should be 'ab123bc.12' - i.e. we have to search to first .
> followed by digits and return it from beginning of string to the last of
> digits.

You could add a negative lookahead to exclude digits after the last match:

... substring(x from E'^(.*?\\.\\d+(?!\\d))') ...

Yours,
Laurenz Albe