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
I guess ITAGAKI meant sizeof(ItemIdData) which is 4 bytes. Thats the data type for the line pointer.