[postgis-devel] Updates to GEOS & POSTGIS

[Ben Jubb]

Tom Lane wrote:
> * memcmp is cheap as long as it hits a diff before proceeding real far.
> You might want to organize the field order with malice aforethought
> so that likely-to-be-different fields appear earlier.
>   
Not possible, i don't have any control over the organization of the 
geometry object.
> * Be sure there are no uninitialized bits hiding anywhere in the struct,
> like in padding bytes between fields.  If you make a practice of zeroing
> the struct (eg with palloc0) before you fill the fields, this should be
> okay.
>   
Not an issue.
> * If you are dealing with float data then there's a small problem: zero
> and minus zero are equal according to the IEEE spec, but not according
> to memcmp.  I think you can probably ignore this for the case of
> deciding whether a cache entry is still valid, since a phony "not equal"
> indication is at worst a performance hit not a correctness problem.
> But it's something to keep at the back of your head.
>   
If this is a problem, i don't think theres anything that can be done 
about it.


Looks like I'm stuck with memcmp().  rats.

b
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