>
>
> Hmm, let me guess ...
>
> one of the overhead elements for each row header is pointer to the next
> row, right ? That way the summing-up of varlena types is avoided, although
> the postgres engine still has to go from row header to row header to find
> Nth row in a page (block), right ?
Sort of. At the start of each row, there is control information. On of
the pieces of information stored is the length of the entire row. Using
that, you can quickly skip to the end of the row.
Because rows can't grow/shrink in place, and only vacuum removes
superseded rows, the next row is right after the end of the current row.
This is getting in to hackers territory. I have set the reply-to
accordingly.
--
Bruce Momjian | http://www.op.net/~candle
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