Re: Performance impact of NULLs and variable length fields

Martijn van Oosterhout wrote:
> Sometime ago somebody asked if it made a difference adn it was suggested
> that the effect was probably marginal. I ran a profiler over postgres doing
> a large query and these are the top 10 functions:
>
> % cumulative self self total
> time seconds seconds calls ms/call ms/call name
> 16.04 0.51 0.51 1676772 0.00 0.00 nocachegetattr
> 11.95 0.89 0.38 1427403 0.00 0.00 heapgettup
> 10.06 1.21 0.32 2955372 0.00 0.00 LockBuffer
> 6.92 1.43 0.22 3406475 0.00 0.00 ExecEvalExpr
> 5.03 1.59 0.16 1617018 0.00 0.00 AllocSetReset
> 4.40 1.73 0.14 1427403 0.00 0.00 heap_getnext
> 4.09 1.86 0.13 1844339 0.00 0.00 ExecEvalVar
> 4.09 1.99 0.13 1441330 0.00 0.00 ReleaseBuffer
> 4.09 2.12 0.13 1427064 0.00 0.00 SeqNext
> 3.46 2.23 0.11 1552338 0.00 0.00 ExecQual

I have added this to the TODO list:

* Improve caching of attribute offsets when NULLs exist in the row

I have some ideas about how offsets with NULL's could be handled in this
case.

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