csv – In the CSVlog mode, is there some way to make PostgreSQL log a custom string bases on some kind of SQL session variable or similar?

I have instructed PostgreSQL to csvlog its errors/notices. Then my script reads these files and put them back into a database table, then deletes the log file. This part is all working and stable.

My issue is that I never know which script is associated with an error/notice. As I have very much established by now, there is no such built-in option.

However, it strikes me that maybe I can send a custom string/text to the PostgreSQL session so that the csvlog includes this field when it makes its CSV log? If so, I could set this “session variable” to the path for my script client-side, and then have PG log the field without itself knowing which script was responsible for the error/notice?

Is this possible? If so, how?

(I already do logging client-side, but that’s just for the actual SQL queries, for statistics purposes. That log doesn’t include any errors/notices; the ones which are logged with the csvlog. I have no idea how I would detect these client-side, if it’s even possible. Everything is very cryptic and difficult in this environment.)

performance – What kind of database is best with conditionals?

I’m looking for the “best” (I know there is probably never an objective best anything) database-kind for chaining conditionals. To use the popular “person” analogy:

I have several characteristics that should all be applied, but it is not known whether all are set.

  • haircolor
  • ZIP-Code
  • brother’s name
  • cat-Owner

A person may have all characteristics filled in or none at all. Assuming the following dataset:

ID:    tobias
color: blonde
cat:   false

ID:    james
cat:   true
zip:   09648

ID:    linda
bro:   john
cat:   false
zip:   01558
color: brown

ID:    ellie
cat:   true

ID:    alice

Querying cat-owners should give ellie, james

Querying brown-haired non-cat-owners should give linda

Data-Set estimation would be 500.000+ entries. With few writes and way more reads.

I thought Graph DBs might be a good idea at first and by making edges the various conditions I could maybe filter the entries relatively easy. Relational Databases would be easy to implement, but my goal is maximum performance so I’m not too sure about that.

macro – What equipment do I need to take these kind of pictures?

Details are described in the Nikon Microscopy University site:

https://www.microscopyu.com/techniques/polarized-light/polarized-light-microscopy

Essentially, you need a microscope that includes a special lightsource designed for polarized light observations, a polarizer, special lenses with interference patterns, rotating stage to get the correct angle, and a digital camera system and extension tube.

It might not surprise you that Nikon is a significant vendor and manufacturer of microscopy solutions.

https://www.microscope.healthcare.nikon.com/products

I doubt this is in many photographer’s ‘hobby budget’. Prices of these are not published, and used equipment on eBay are priced at $18,000 USD.

A possible kind of $K$ theory via comparison of sphere bundles associated to given vector bundles

Let $E$ be a vector bundle on a topological space $X$.Thanks to Allen Hatcher’s book “Vector Bundles and K theory”, the construction of sphere bundle $S(E)$ can be done without any inner product on fibers. It is a result of the equivalent relation on each punctured fiber: $vsim w$ if $v=lambda w$ for some positive scalar $lambda$.

We define an equivalent relation on the set of all vector bundles over $X$ as follows: $E$ is equivalent to $F$ if their corresponfing sphere bundles $S(E)$ and $S(F)$ are isomorphic fiber bundles.

Is the above equivalent relation compatible to direct sum and tensor product of vector bundles in the following sense;

If $E_1,E_2$ are equivalent bundles and $F_1,F_2$ are also equivalent bundles in the above sense, are $E_1oplus F_1, E_2 oplus F_2$ are equivalent bundles? What about the tensor product, instead of direct sum?
Can this equivalent relation define a kind of $K$ theory?

Which kind of nasm is more suitable for a career in software engineering

This question has been bothering me. I have been learning nasm for linux systems and I feel it is much easier to understand compared to nasm for windows. They have different syntax each and I want to focus on one. Which of the two do you guys see as more commonly in use in a career in software engineering and why? I can be flexible in development for windows and linux.

Scrap any kind of website data for $5

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Lower bounds on the modified Bessel function of the first kind

It is known that the modified Bessel function $I_{n}(x)$ satisfies the lower bound

begin{eqnarray*}
I_{n}(x) > frac{1}{Gamma(n+1)} left( frac{x}{2} right)^n
end{eqnarray*}

for $x > 0$, $n > -frac{1}{2}$. This lower bound is pretty good when $x$ is small, but it loses tightness when $x$ is about the same size as $n$; the plot below shows this discrepancy in a logarithmic scale for $I_{20}(x)$ (the dashed curve is the lower bound):

enter image description here

A better lower bound for $I_n(x)$ likely has to incorporate the term $e^{x}$ that is found in its asymptotic expansion:

begin{eqnarray*}
I_{n}(x) sim frac{e^{x}}{sqrt{2 pi x}}left( 1 – frac{4n^2 -1}{8x} + cdots right)
end{eqnarray*}

I have not been able to find such a lower bound thus far.

On a kind of HIT

Let us work over a number field $k$. Let $C$ be a smooth, rational curve and $Xto C$ be a family of smooth, projective hyperbolic curves such that $X(k)to C(k)$ is surjective.

If $X$ has Kodaira dimension 2 and we assume that the Bombieri-Lang conjecture holds, then the rational points of $X$ are not dense and thus by Hilbert irreducibility we can conclude that there exists a section $Cto X$.

Question 1: is the Bombieri-Lang conjecture really necessary? I have this gut feeling that the finiteness of rational points of an hyperbolic curve should be enough, and that Kodaira dimension 2 is not necessary, but I cannot conclude.

Question 2: as a consequence of Hilbert irreducibility, if $C_1to C_2$ is a map of curves such that $C_1(k’)to C_2(k’)$ is surjective for every finite extension $k’/k$, then there exists a section $C_2to C_1$. In the setting above, if we remove the assumption that $C$ is rational and instead ask that $X(k’)to C(k’)$ is surjective for every finite extension $k’$, can we still conclude that a section exists?

What kind of head or adaptor do I need to mount a camera on a Celestron tripod?

Unlike the photography industry, the astronomy industry doesn’t necessarily have a standard for tripod mounts per se and most adapters are custom-made. In other words, the “tripod” and “head” are typically sold as a matched pair (and may have some proprietary way of attaching) but often the telescope mount itself (what a photography might think of as the “head”) will have either an industry standard mounting saddle (there are two… the Vixen style and the Losmandy style) or a completely proprietary mounting method (low-priced telescopes sold as a complete kit often use a completely proprietary mounting method but more expensive mounts tend to use one of the industry standards because they realize those astronomers will mix & match equipment to fit their needs).

While your tripod isn’t using any industry standard … it should still be relatively easy and inexpensive to adapt this for photographic use. This is because in the photography industry, there is a standard. Photographic camera heads nearly always use a 3/8″ threaded mounting hold with 16 threads per inch (commonly abbreviated as 3/8″-16 … or 3/8″-16tpi). This means you can attach nearly any photographic camera head to nearly any photographic tripod as long as they use that particular thread size. So to make this work… you just need a way to use a 3/8″-16 threaded rod with your tripod.

  1. Measure the hole on the tripod and make sure it can accommodate a 3/8″ threaded rod (likely it can).

  2. Select the photographic tripod head of your choice and verify that it has a 3/8″-16 mounting hole in the base.

  3. You will then need a 3/8″-16 threaded rod to go into the base of your tripod head and then put the other end of the rod through that hole on the tripod. Measure the length you need and it’s ok if it’s a bit long. Just make sure it isn’t a bit short. McMaster-Carr is a popular online website for ordering all sorts of threaded parts and in whatever material or length you need (and I would probably select stainless). See: https://www.mcmaster.com/threaded-rods/stainless-steel-threaded-rods/

  4. Lastly, you’ll need a knob with a 3/8″-16 threaded hole… like this one: https://www.woodcraft.com/products/knob-five-star-with-through-hole-3-8-16-insert (I did a web-search for 3/8″-16 knob and this was just one of many examples that came up in the search results). You should also use a washer (between the knob and tripod). Since this knob allows the threaded rod to pass completely through the knob to the other side… being “too long” wont be a problem.

And that should do it!