grogers

24 ms·

241.
by grogers 8y ago
Another neat autonomous boat concept is https://www.liquid-robotics.com/wave-glider/how-it-works/ which uses waves for propulsion.
242.
by grogers 8y ago
Select * is useful if you are adding columns. You can either read the column or supply a default if the column doesn't exist. Doing this by having two queries naming different lists of columns is much worse, although it's unavoida
243.
by grogers 8y ago
Great post about how to attack solving a problem using DP. But this is not a good interview question. It's a toy problem, not something you'll ever need to solve in real life. Maybe if you squint hard enough it's close to pat
244.
by grogers 8y ago
There needs to be at least some emphasis on fatalities. If autopilot reduces total collisions but increases fatalities, you might draw the wrong conclusion about its safety. It's early but from the incidents we know already, it seems l
245.
by grogers 8y ago
I think the main difference is that restore will create a new DB instance, whereas backtrack updates the state of the DB instance in place. It is also probably a lot faster than restoring.
246.
by grogers 8y ago
I think the point was that profile guided optimization relies on the workload staying relatively fixed. If the workload suddenly changes (like promoting a readonly slave to be the writable master) the assumptions made by PGO may not be vali
247.
by grogers 9y ago
Luckily taking 15 seconds to type this in the address bar and load the old version is still faster than loading any "normal" mobile Reddit page. This is what I've been doing for years.
248.
by grogers 9y ago
Yes, the problem is that you don't know the car has done something stupid until after it's already happened. By then, it's likely too late because obstacles on the road are very nearby. It might not solve all these accidents
249.
by grogers 9y ago
Is it really much extra work to do the migration online instead of offline? It's just that second step where the application writes to both tables (and usually a step where reads switch to the new tables). Everything else is necessary
250.
by grogers 9y ago
This is essentially what innodb does, it calls this operation "purge" as in purging dead mvcc rows, and it calls the data structure the history list (IIRC). I don't know what the exact data structure is though to find purgabl
251.
by grogers 9y ago
It's not so much the difference between simple and complex carbohydrates, but between glucose and fructose. Glucose is energy for your body, so important you will manufacture it even on a zero carbohydrate diet. Fructose serves no real
252.
by grogers 9y ago
I agree to an extent, spanner showed that point in time global snapshots can be practical. But many (most?) applications are fine with just serializable transactions, they don't need the additional real-time preserving guarantee of str
253.
by grogers 9y ago
https://en.m.wikipedia.org/wiki/Gustafson%27s_law
254.
by grogers 9y ago
When you are jumping large numbers of pages, you usually don't care about exact page boundaries. For example, you could have a background process that slowly paginates through the table and saves off the page boundaries, which you can
255.
by grogers 9y ago
To expand on this, NTP uses timestamps with 32 bit seconds (plus fractions of a second), so if you manually step your clock some multiple of ~136 years, the protocol inputs will be the exact same so you'd have no way of knowing you wer
256.
by grogers 9y ago
MySQL has similar issues to postgres vacuum. If 'checkpoint age' gets too high throughput drops by ~5x to prevent WAL wrapping. We hit this in production when using 5.5. They've made a lot of improvements to flushing in recen
257.
by grogers 9y ago
It might be a good choice to switch to postgres, but it isn't like MySQL isn't innovating too. 8.0 will have a ton of features. This includes a bunch of "catch up" things like CTEs and SKIP LOCKED, but also stuff like sy
258.
by grogers 9y ago
> It says that the probability is not zero. That is a very important distinction for some people I'm not a mathematician, but I'm pretty sure it doesn't even say the probability of failed consensus must be nonzero. For exa
259.
by grogers 9y ago
Using FLP to say that atomic broadcast is impossible is overly simplistic. In the real world, where people do use atomic broadcast/consensus in real distributed systems, it just isn't a problem. FLP says it's always possible
260.
by grogers 9y ago
For me it was the casing. We aren't used to seeing "Pairs" capitalized, especially so since it is not the first word in the sentence. Paris however, will always be capitalized, so the brain autocorrects to the wrong word. Ev
261.
by grogers 9y ago
My confusion (and I suspect others) is about what it means for &T to be Sync. Cell<T> isn't safe to be shared across threads (so isn't Sync) but it is Send if T:Send. But that means &Cell<T> is Sync? You can sh
262.
by grogers 9y ago
Will adaptive hash index ever be disabled by default? While it's orders of magnitude less horrible than the query cache, it's in the same category of things which add variance for marginal gain.
263.
by grogers 10y ago
I haven't done any in depth analysis of gryadka but I think the premise of the argument here may be wrong. Even if a particular value isn't accepted by a majority of nodes, that doesn't necessarily make it a dirty read. As lo
264.
by grogers 10y ago
It's strange that I can't find anything on implementing a CAS register this way. It seems like a relatively straightforward combination of single-decree paxos and the ABD algorithm. Of course, reasoning about distributed algorithm
265.
by grogers 10y ago
This is precisely why cells (alluded to in the write-up) are beneficial. If the size of a cell is bounded and you scale by adding more cells, testing the breaking point of the largest cell becomes an easier problem. There is still usually a
266.
by grogers 10y ago
Are read-only transactions handled without contention? I understand that a read-write transaction needs to be aborted if a later conflicting write is committed. But read-only transactions can view a snapshot of what was committed before the
267.
by grogers 10y ago
Having never used postgres, this seems extremely scary. I've only ever needed index hints a couple times in other databases, but when you need them there isn't usually an alternative. Messing with global knobs is a good way to cau
268.
by grogers 10y ago
If you structure your graph as an adjacency matrix/list, you can do it in rust. There are some optional GC proposals so you could build ad-hoc graphs of objects, but nothing concrete (it's gonna be a while). In general when buildi
269.
by grogers 10y ago
Resending and reencrypting the message mean the same thing here, I don't understand the distinction. Once the user okays the key change it can be resent by encrypting with the new key, before that it would be blocked from being resent.
270.
by grogers 10y ago
Does anybody have an example of an application where you need the counting/deletion properties of a counting bloom filter or cuckoo filter over a normal bloom filter? If you do, how do you deal with the filter rejecting your writes bec

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