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
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