proposed PQconnectdbParams macros (was Re: [BUGS] BUG #5304: psql using conninfo fails in connecting to the server)

[moving to hackers]

On 02/02/2010 10:23 PM, Tom Lane wrote:
> Joe Conway <mail(at)joeconway(dot)com> writes:
>> Should I also be looking to replace all (or most) other instances of
>> PQsetdbLogin()?
>
> I think we at least wanted to fix pg_dump(all)/pg_restore. Not sure if
> the others are worth troubling over.

Any objection if I add these two macros to libpq-fe.h?
-------------------
+ /* Useful macros for PQconnectdbParams() and PQconnectStartParams() */
+ #define DECL_PARAMS_ARRAYS(PARAMS_ARRAY_SIZE) \
+ const char **keywords = pg_malloc(PARAMS_ARRAY_SIZE * \
+ sizeof(*keywords)); \
+ const char **values = pg_malloc(PARAMS_ARRAY_SIZE * \
+ sizeof(*values))
+ #define SET_PARAMS_ARRAYS(__kv_idx__,__kv_kw__,__kv_v__) \
+ keywords[__kv_idx__] = __kv_kw__; \
+ values[__kv_idx__] = __kv_v__

That way this:
-------------------
! #define PARAMS_ARRAY_SIZE 7
! const char **keywords = pg_malloc(PARAMS_ARRAY_SIZE *
! sizeof(*keywords));
! const char **values = pg_malloc(PARAMS_ARRAY_SIZE *
! sizeof(*values));
!
! keywords[0] = "host";
! values[0] = options.host;
! keywords[1] = "port";
! values[1] = options.port;
! keywords[2] = "user";
! values[2] = options.username;
! keywords[3] = "password";
! values[3] = password;
! keywords[4] = "dbname";
! values[4] = (options.action == ACT_LIST_DB &&
! options.dbname == NULL) ?
! "postgres" : options.dbname;
! keywords[5] = "fallback_application_name";
! values[5] = pset.progname;
! keywords[6] = NULL;
! values[6] = NULL;

becomes this:
-------------------
! DECL_PARAMS_ARRAYS(7);

! SET_PARAMS_ARRAYS(0,"host",options.host);
! SET_PARAMS_ARRAYS(1,"port",options.port);
! SET_PARAMS_ARRAYS(2,"user",options.username);
! SET_PARAMS_ARRAYS(3,"password",password);
! SET_PARAMS_ARRAYS(4,"dbname",(options.action == ACT_LIST_DB &&
! options.dbname == NULL) ?
! "postgres" : options.dbname);
! SET_PARAMS_ARRAYS(5,"fallback_application_name",pset.progname);
! SET_PARAMS_ARRAYS(6,NULL,NULL);

I suppose if we do this maybe we should also do:
#define PARAMS_KEYWORDS keywords
#define PARAMS_VALUES values

so the subsequent use looks like:

pset.db = PQconnectdbParams(PARAMS_KEYWORDS, PARAMS_VALUES, true);

To me it seems easier to read and less error prone. Comments?

Joe