Re: Keywords in pg_hba.conf should be field-specific

On 18 October 2010 01:19, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Brendan Jurd <direvus@gmail.com> writes:
>> On 17 October 2010 09:59, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>>> Good point.  Maybe the correct fix is to remember whether each token was
>>> quoted or not, so that keyword detection can be done safely after the
>>> initial lexing.  I still think that the current method is impossibly
>>> ugly ...
>
>> I'm happy to revise the patch on that basis.  Any suggestions about
>> how to communicate the 'quotedness' of each token?  We could make each
>> token a struct consisting of the token itself, plus a boolean flag to
>> indicate whether it had been quoted.  Does that work for you?
>
> Seems reasonable.  I had the idea of a parallel list of booleans in the
> back of my mind, but a list of structs is probably easier to understand,
> and to extend further if necessary.
>

Okay, I've taken the red pill and I'm finding out how deep the rabbit
hole goes ...

The logical structure of pg_hba.conf is a set of lines, each line
containing a set of fields, each field containing a set of tokens.
The way the existing implementation handles this is to create a list
of lines containing sublists of fields, containing comma-separated
strings for the set of tokens, with newlines embedded next to tokens
which might be keywords.

The tokeniser breaks apart the comma-separated tokens ... and then
reassembles them into a comma-separated string.  Which the db/role
matching functions then have to break apart *again*.

In order to keep track of whether each individual token was quoted, I
first need to impose some sanity here.  Rather than using a magical
string for each field, I intend to use a List of HbaToken structs
which explicitly note whether quoting was used.

Introducing an extra List level does mean a bit more work copying and
freeing, and it makes the patch really quite intrusive.  I have to
touch a lot of lines in hba.c, but I think the additional clarity is
worth it.  If nobody dissuades me from this approach I hope to post a
patch in a couple of days.

Cheers,
BJ