[Bizgres-general] Re: Latest bitmap patch results. (tuple offset out of range)

[Jie Zhang]

Mark,

> On a related note, earlier Simon and I did a few calculations concerning 
> how many tuples fit on a heap page - well looks like we should have 
> examined tidbitmap.c where this is calculated more conservatively:

> (src/backend/nodes/tidbitmap.c):
> #define MAX_TUPLES_PER_PAGE  ((BLCKSZ - 1) / 
> MAXALIGN(offsetof(HeapTupleHeaderData, t_bits) + sizeof(ItemIdData)) + 1)

> Now Bizgres is using (src/include/access/bitmap.h):

> #define MaxNumHeapTuples    ((OffsetNumber) 
> (BLCKSZ/sizeof(HeapTupleHeaderData)))

> These work out at 256 and 292 respectively, for the typical case - 
> perhaps the same calculation should be used in bitmap.h?

I agree, and will make this change.

Best,
Jie