Re: portability of "designated initializers"

Tom Lane wrote:
> Alvaro Herrera <alvherre@commandprompt.com> writes:
> > I've already modified your patch a bit ... please send your updated
> > patch so I can merge it into mine.  However, my changes were also
> > relatively minor.  Since Tom wants it to be entirely rewritten then
> > maybe merging minor fixes to it is a waste of time ...
> 
> The thing I'm complaining about is having dropped the intermediate
> struct that represents the fully decoded set of reloptions.  If you
> put that back I won't object to a table-driven approach to doing the
> decoding.

Do we need a struct, or can we get away with storing the values directly
in RelationData?  Something like this:

typedef struct RelationData
{...
/* * Parsed values from reloptions.  These are set whenever rd_rel is loaded * into the relcache entry. */bool
autovacuum_enabled;int       fillfactor;int        autovacuum_vacuum_threshold;int
autovacuum_analyze_threshold;int       autovacuum_vacuum_cost_delay;int        autovacuum_vacuum_cost_limit;int
autovacuum_freeze_min_age;int       autovacuum_freeze_max_age;float8    autovacuum_vacuum_scale_factor;float8
autovacuum_analyze_scale_factor;

One problem is that this enlarges Relation by a fair bit for every
relation, even those that are never concerned with autovacuum, e.g.
indexes.  I'm not sure how much is this a problem in practice.  (It
could become a problem for people who has thousands of partitions, but
we don't actually support that.)

I have also modified the patch to include the default value for each
option in the table; to solve the problem of differing fillfactors for
the different index AMs, I've created separated "kinds" this way:

/* kind supported by reloptions */
#define    RELOPT_KIND_NULL    (1 << 0)
#define    RELOPT_KIND_HEAP    (1 << 1)
#define    RELOPT_KIND_BTREE    (1 << 2)
#define    RELOPT_KIND_HASH    (1 << 3)
#define    RELOPT_KIND_GIN        (1 << 4)
#define    RELOPT_KIND_GIST    (1 << 5)

so we can do something like this:
{    {        "fillfactor",        "Packs table pages only to this percentage",        RELOPT_TYPE_INT,
RELOPT_KIND_HEAP   },    HEAP_DEFAULT_FILLFACTOR, HEAP_MIN_FILLFACTOR, 100},{    {        "fillfactor",        "Packs
btreeindex pages only to this percentage",        RELOPT_TYPE_INT, RELOPT_KIND_BTREE    },    BTREE_DEFAULT_FILLFACTOR,
BTREE_MIN_FILLFACTOR,100}, ... more for the other AMs ...
 


Is that approach OK?

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.