Andres Freund <and...@2ndquadrant.com> writes:
> On 2014-09-13 08:52:33 +0300, Ants Aasma wrote:
>> On Sat, Sep 13, 2014 at 6:59 AM, Arthur Silva <arthur...@gmail.com> wrote:
>>> That's not entirely true. CRC-32C beats pretty much everything with the same
>>> length quality-wise and has both hardware implementations and highly
>>> optimized software versions.
>> For better or for worse CRC is biased by detecting all single bit
>> errors, the detection capability of larger errors is slightly
>> diminished. The quality of the other algorithms I mentioned is also
>> very good, while producing uniformly varying output.
> There's also much more literature about the various CRCs in comparison
> to some of these hash allgorithms.
Indeed. CRCs have well-understood properties for error detection.
Have any of these new algorithms been analyzed even a hundredth as
thoroughly? No. I'm unimpressed by evidence-free claims that
something else is "also very good".
Now, CRCs are designed for detecting the sorts of short burst errors
that are (or were, back in the day) common on phone lines. You could
certainly make an argument that that's not the type of threat we face
for PG data. However, I've not seen anyone actually make such an
argument, let alone demonstrate that some other algorithm would be better.
To start with, you'd need to explain precisely what other error pattern
is more important to defend against, and why.
regards, tom lane
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