Re: Re: Allow Reg Expressions in Position function

On Mon, 20 Aug 2018 at 09:22, Nick Dro <postgresql(at)walla(dot)co(dot)il> wrote:

>
> This incorrect.
> SELECT position(substring('https://www.webexample.com/s/help?' FROM
> '/(s|b|t)/') IN 'https://www.webexample.com/s/help?');
>
> Gives 5. It's wrong.
>

On Mon, 20 Aug 2018 at 09:22, Nick Dro <postgresql(at)walla(dot)co(dot)il> wrote:

>
> This incorrect.
> SELECT position(substring('https://www.webexample.com/s/help?' FROM
> '/(s|b|t)/') IN 'https://www.webexample.com/s/help?');
>
> Gives 5. It's wrong.
>

For some reason, substring() returns the parenthesised subexpression rather
than the top level.

The comment in testregexsubstr does say that it does this, but it's not
clear from the documentation at all, unless I'm missing where it says it.

You can work around this by putting parentheses around the whole
expression, because that way the first subexpression is the whole match.

db=# SELECT position(substring('https://www.webexample.com/s/help?' FROM
'(/(s|b|t)/)') IN 'https://www.webexample.com/s/help?');
position
----------
27

Geoff