APT update fails: writing more data than expected
Trouble downloading packages list due to a "Hash sum mismatch" error
Override back button to act like home button Why this JSFiddle does not work Say, we have a query like this:  select a.*,b.* from  a join b on a.col1=b.col1 and len(a.col1)=10   Assuming the above query uses a Hash Join and has a residual, the probe key will be col1 and the residual will be len(a.col1)=10.  But while going through another example, I could see both the probe and the residual to be the same column. Below is an elaboration on what I am trying to say:  Query:  select * from T1 join T2 on T1.a = T2.a    Execution plan, with probe and residual highlighted:         Test data:    create table T1 (a int, b int, x char(200)) create table T2 (a int, b int, x char(200))  set nocount on declare @i int set @i = 0 while @i &lt; 1000   begin       insert T1 values (@i * 2, @i * 5, @i)     set @i = @i + 1   end  declare @i int set @i = 0 while @i &lt; 10000   begin     insert T2 values (@i * 3, @i * 7, @i)     set @i = @i + 1   end   Question:    How can a probe and a residual be the same column? Why can't SQL Server use the probe column only? Why does it have to use the same column as a residual to filter rows again?  References for test data: Man is sitting in his room and gets contradictory advice from two men from the future Live refresh shows "modified" on tagged questions even when unmodified $\{\emptyset\}$ is a set containing the empty set. Is $\{\emptyset\}$ a subset of $\{\{\emptyset\}\}$?  My hypothesis is yes by looking at the form of "the superset $\{\{\emptyset\}\}$" which contains "the subset $\{\emptyset\}$". What is the "canary thread" and why is it starving? The following occasionally appears in /var/log/syslog:  rtkit-daemon[1145]: The canary thread is apparently starving. Taking action. rtkit-daemon[1145]: Demoting known real-time threads. rtkit-daemon[1145]: Successfully demoted thread 1431 of process 1368 (n/a). rtkit-daemon[1145]: Successfully demoted thread 1430 of process 1368 (n/a). rtkit-daemon[1145]: Successfully demoted thread 1368 of process 1368 (n/a). rtkit-daemon[1145]: Demoted 3 threads.   What's going on here? Set origin to bottom center of multiple objects I have a lot of 3D objects of various sizes, shapes in blender 2.76b and I would like to set the origin to the bottom center of the objects bounds.  I cannot select the bottom edge and snap to cursor etc as each shapes edges are in different X/Y positions.  Is there a script or tool that will allow me to set the origin to the lowest edge z position? Sort order issue I'm having an issue sorting data in ascending order.   Right now the sort order is: 1.0.0  10.0.0 10.0.1 11.0.0 2.0.0 2.0.1 3.0.0 3.0.1 3.1.0  What I want is: 1.0.0 2.0.0 2.0.1 3.0.0 3.0.1 3.1.0 10.0.0 10.0.1 11.0.0  How can I achieve this? The datatype can't be number or currency because of the 2 decimals, so I used text-field. Is there an online community to find travel partners (for mountains, sightseeing etc.)? Is there an online community to find travel partners for mountain trekking or sightseeing, or anything else?  I don't want to travel to foreign mountains alone, but I don't know where to search for company. There's a great community for accommodation (I mean CouchSurfing) so I think there should be something in "reverse" direction (searching not the place to stay but the people to go with). says that the number of different monomials of degree $M$ in $N$ variables is $$\frac{(M+N-1)!}{M!(N-1)!}\; .$$ Can anyone explain why this is true? Python BeautifulSoup findAll by "class" attribute Isomorphism involving Eilenberg-Maclane space, Tors. Let $\pi$ be a group and let $K(\pi, 1)$ be a connected CW complex such that $\pi_1(K(\pi, 1)) = \pi$ and $\pi_q(K(\pi, 1)) = 0$ for $q \neq 1$. Does there exist an isomorphism between $H_*(K(\pi, 1); A)$ and $\text{Tor}_*^{\mathbb{Z}[\pi]}(A, \mathbb{Z})$? Can all real polynomials be factored into quadratic and linear factors? So I understand how to do integration on rational functions with a linear and a quadratic denominator, and I understand how to do a partial fraction decomposition, but I was wondering what happens if the polynomial is higher degree and can't be factored. Later in the page, it says this:     However, it can be shown that any polynomial with real coefficients is a product of linear and/or irreducible quadratic factors with real coefficients.   And I was wondering, how do we know this and is this definitely true? How do I install drivers for the Atheros AR8161 Ethernet controller? How to find the mime type of a file in python? Let's say you want to save a bunch of files somewhere, for instance in BLOBs. Let's say you want to dish these files out via a web page and have the client automatically open the correct application/viewer.  Assumption: The browser figures out which application/viewer to use by the mime-type (content-type?) header in the HTTP response.  Based on that assumption, in addition to the bytes of the file, you also want to save the MIME type.  How would you find the MIME type of a file? I'm currently on a Mac, but this should also work on Windows.   Does the browser add this information when posting the file to the web page?  Is there a neat python library for finding this information? A WebService or (even better) a downloadable database? Calculate sum of series $\sum \frac{n^2}{n!}$ I have to calculate sum of series $\sum \frac{n^2}{n!}$. I know that $\sum \frac{1}{n!}=e$ but I dont know how can I use that fact here.. I am a n00b to physics. What physics I know comes from high school and popular science books.  At school we were taught about atoms and what make up atoms, but we weren't actually told what the particles were!  So sure an atom has electrons orbiting around a nucleus made of protons and neutrons, but what exactly is an ?  And if we don't know, how can we fire them from guns, like they do in experiments ... etc  Any clarification on this would be great. How does a wheelie work? So I've been trying to create a mathematical model for an electric motorcycle and began to wonder about the maximum possible torque that could be supplied to the rear driven wheel without having the bike begin to lift up on one wheel.  I found ways to calculate this value online; however, the basic concept as to how the bike actually lifts escapes me.    My problem started when I began to think about what axis the bike will rotate about when it is doing the wheelie.  My first intuition was that the frame and front wheel, together, rotate about the rear axle.  But when I drew a free body diagram of the frame/front wheel system just at liftoff (see below) I made note that the only forces acting about the rear axle, point O, is the force of weight.  This means that an increase in applied torque and subsequently, the applied force Fa, should not effect the rotation about the rear axle.  I know that the applied force on the back wheel is indeed correlated with the propensity for a bike to wheelie, so I considered that the axis of rotation I was choosing was wrong.  If we take the free body diagram above and sum the moments about the center of mass, we would find that an increased applied force would in fact cause the solid body to rotate.  The problem with this understanding is that during rotation, the center of mass of the drawn system should actually rises relative to the surface the bike is moving across.  If the bike were to be truly rotating about its center of mass, then the back wheel would begin to dip below the surface of the road like you might see in a glitchy video game.    So I suspect that the bike is in fact rotating about the back axle, but I don't understand why, please help!  edit: I added the external torque from the back wheel to the frame, which would allow the bike to rotate about the back axle  edit 2:  I suppose that the torque acting on the frame via the engine should not effect the rotation as the movement of a motorcycle can be perfectly replicated by applying a force at the back axle.  A third possible axis of rotation might be the lowest point of the back wheel. Green is the most common circuit-board color because it has become an industry standard.  What I'm interested in is How the traditional "PCB Green" become a standard in the first place?   Were there any interesting historical reasons for the initial choice, or was it just a product of what one particularly successful company was doing that became the de-facto standard?