Re: Bit data type header reduction in some cases

Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> writes:
> On 02/25/2014 08:23 AM, Haribabu Kommi wrote:
>> It's regarding a Todo item of "Bit data type header reduction" in some
>> cases. The header contains two parts. 1) The varlena header is
>> automatically converted to 1 byte header from 4 bytes in case of small
>> data. 2) The bit length header called "bit_len" to store the actual bit
>> length which is of 4 bytes in size. I want to reduce this bit_len size to 1
>> byte in some cases as similar to varlena header. With this change the size
>> of the column reduced by 3 bytes, thus shows very good decrease in disk
>> usage.

> [ various contorted schemes for doing that backward-compatibly ]

TBH, this sounds like a huge amount of effort and a significant risk of
new bugs in return for not darn much. Who uses bit values anyway?
They were removed from the SQL spec more than 10 years ago. And of that
population, who cares about a byte or two per value? The field demand
for this is not only zero, it's probably negative. (The thread referenced
by the TODO entry shows no evidence of user demand.)

regards, tom lane