Re: Free space management within heap page

ITAGAKI Takahiro wrote:
> BLCKSZ is typically 8192 bytes and sizeof(ItemPointerData) is 4 bytes.
> 1/4 comes from 8192 / 4 = 2048. If we allow zero-size tuples, the line
> pointers area can bloat up to the ratio. We have tuples no less than
> 32 bytes-size, so the area is restricted 256 bytes now.

sizeof(ItemPointerData) == 6 bytes

> We can recycle unused line pointers, but we cannot shrink the area unless
> the tail end of line pointers are removed. i.e, unusable free space will
> remains at the middle of LP area. 

Yeah, agreed. It'd still be a good idea to do it when possible.

--   Heikki Linnakangas  EnterpriseDB   http://www.enterprisedb.com