On 11/10/06, Tom Lane <tgl@sss.pgh.pa.us > wrote: "Pavan Deolasee" <pavan.deolasee@gmail.com> writes:
> Yes. The last bit in the t_infomask is used up to mark presence of overflow
> tuple header. But I believe there are few more bits that can be reused.
> There are three bits available in the t_ctid field as well (since ip_posid
> needs maximum 13 bits).
No, you cannot have those bits --- BLCKSZ is not limited to 8K, and even
if it were, we will not hold still for sticking flag bits into an
unrelated datatype.
BLCKSZ is not limited to 8K, but it is limited to 32K because of lp_off and lp_len
which are 15 bits in size.
OffsetNumber is limited to (BLCKSZ / sizeof(ItemIdData)). Since sizeof(ItemIdData) is 4 bytes, MaxOffsetNumber is 8192. So we need only 13 bits to represent the MaxOffsetNumber.
Regards,
Pavan