include/config.h FOLLOWUP

I just wrote about issues regarding upping the max blocksize.  There is
stuff in storage/itemid.h that would need to be modified (also in
bufmgr.h, but that is trivial).  Th idea is that:

typedef struct ItemIdData
{
                                                  /* line pointers */
        unsigned        lp_off:13,              /* offset to find tup */
        /* can be reduced by 2 if necc. */
                                lp_flags:6,             /* flags on tuple */
                                lp_len:13;              /* length of
tuple */
} ItemIdData;

the  ItemIdData.lp_len is maxed at 2^13, or 8192.  My query then is:
which of the items is it saying 'can be reduced by 2 if necc'?  For, if
that is accurate, I'd like to e.g. lp_off:11 and lp_len:15, allowing for
tuples of 32768 or something.  And also not breaking the nice 32 bit
length of the struct.

Lemme know...

ps. why not allow for larger tuples in general?  Do we take a speed hit?

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