It would seem there is a fair deal of call for an updated version of my PhpED dark theme from colleagues as well as random folks on the internet who’ve seen screenshots of my PhpED installation. I previously had my Dark Theme for 5 linked on my Review of PhpED, but I figured I could have a page dedicated to it. Screenshots Download and Installation The first step is to download the proper version. Click here to download the ....
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Problem: Show 31.5 = 32.5. “Solution”: Explanation: It appears that by shifting around the pieces of one triangle, we have constructed a second figure which covers less area! Since the first triangle has base length 13 and height 5, its area is 32.5. Clearly, the second figure has the same area minus a square of area 1, giving the second figure area 31.5. In fact, by counting up the squares in each component, we do see that it is simply a s..
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Problem: Show 31.5 = 32.5. “Solution”: Explanation: It appears that by shifting around the pieces of one triangle, we have constructed a second figure which covers less area! Since the first triangle has base length 13 and height 5, its area is 32.5. Clearly, the second figure has the same area minus a square of area 1, giving the second figure area 31.5. In fact, by counting up the squares in each component, we do see that it is simply a s..
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Problem: Show 31.5 = 32.5. “Solution”: Explanation: It appears that by shifting around the pieces of one triangle, we have constructed a second figure which covers less area! Since the first triangle has base length 13 and height 5, its area is 32.5. Clearly, the second figure has the same area minus a square of area 1, giving the second figure area 31.5. In fact, by counting up the squares in each component, we do see that it is simply a s..
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Today the Panasonic Insider Crew (Maybe I’ll shorten this to PIC from now on) home was launched in its own little corner of the web (the “Insider Crew Home”) and I was invited to be one of the beta testers. It’s good to see Soup making progress with the Insider Crew. Many of you know that I’ve had my doubts about the Insider Crew before, but with the Home Entertainment Launch event and now a dedicated PIC Home for the members it’s clear tha..
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The MySQL curtime function has (at least) the following issues: The function returns the current time as a number i.e. the time quarter past 8 would be returned from the function as the number 201500. (So if you subtract one from such a number you get 201499 which has no meaning.) The function only returns this if you use it in an “integer context”, i.e. (x+0) causes x to be evaluated to an integer. (Otherwise it produces a string i....
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What is the purpose of segment level checkpoint before DROP/TRUNCATE of a table?
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tanelpoder.com
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14 years ago
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eng
There was a very good question asked in Oracle-L list today, which has bothered me too in past. The question was: What is the purpose of a segment level checkpoint before DROP/TRUNCATE of a table? In other words, why do we have to wait for the enq: RO - fast object reuse wait event (and in 11.2 the enq: CR - block range reuse ckpt wait) when dropping and truncating segments? I’m not fully confident that I completely know..
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What is the purpose of segment level checkpoint before DROP/TRUNCATE of a table?
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tanelpoder.com
-
14 years ago
-
eng
There was a very good question asked in Oracle-L list today, which has bothered me too in past. The question was: What is the purpose of a segment level checkpoint before DROP/TRUNCATE of a table? In other words, why do we have to wait for the enq: RO - fast object reuse wait event (and in 11.2 the enq: CR - block range reuse ckpt wait) when dropping and truncating segments? I’m not fully confident that I completely know..
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So my attitude for most of this year has been one of reserving judgement in favor of direct experience. As part of this, I have been trying all the latest "Kool-Aid" web development technologies even if at first glance they didn't sit right with me. So I started building the Othenticate infrastructure on a shiny stack of mongodb, node.js, express, mongoose, jade, and stylus. For the most part, I love this stack. However, after I while I h....
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Problem: Show there are finitely many primes. “Solution”: Suppose to the contrary there are infinitely many primes. Let $ P$ be the set of primes, and $ S$ the set of square-free natural numbers (numbers whose prime factorization has no repeated factors). To each square-free number $ n \in S$ there corresponds a subset of primes, specifically the primes which make up $ n$’s prime factorization. Similarly, any subset $ Q \subset P$ of primes..
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Problem: Show there are finitely many primes. “Solution”: Suppose to the contrary there are infinitely many primes. Let $ P$ be the set of primes, and $ S$ the set of square-free natural numbers (numbers whose prime factorization has no repeated factors). To each square-free number $ n \in S$ there corresponds a subset of primes, specifically the primes which make up $ n$’s prime factorization. Similarly, any subset $ Q \subset P$ of primes..
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Problem: Show there are finitely many primes. “Solution”: Suppose to the contrary there are infinitely many primes. Let $ P$ be the set of primes, and $ S$ the set of square-free natural numbers (numbers whose prime factorization has no repeated factors). To each square-free number $ n \in S$ there corresponds a subset of primes, specifically the primes which make up $ n$’s prime factorization. Similarly, any subset $ Q \subset P$ of primes..
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This is the first in a series of “false proofs.” Despite their falsity, they will be part of the Proof Gallery. The reason for putting them there is that often times a false proof gives insight into the nature of the problem domain. We will be careful to choose problems which do so. Problem: Show 1 = 2. “Solution”: Let $ a=b \neq 0$. Then $ a^2 = ab$, and $ a^2 – b^2 = ab – b^2$.
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This is the first in a series of “false proofs.” Despite their falsity, they will be part of the Proof Gallery. The reason for putting them there is that often times a false proof gives insight into the nature of the problem domain. We will be careful to choose problems which do so. Problem: Show 1 = 2. “Solution”: Let $ a=b \neq 0$. Then $ a^2 = ab$, and $ a^2 – b^2 = ab – b^2$.
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This is the first in a series of “false proofs.” Despite their falsity, they will be part of the Proof Gallery. The reason for putting them there is that often times a false proof gives insight into the nature of the problem domain. We will be careful to choose problems which do so. Problem: Show 1 = 2. “Solution”: Let $ a=b \neq 0$. Then $ a^2 = ab$, and $ a^2 – b^2 = ab – b^2$.
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Problem: $ \frac{1}{2} + \frac{1}{4} + \frac{1}{8} + \dots = 1$ Solution: Problem: $ \frac{1}{3} + \frac{1}{9} + \frac{1}{27} + \dots = \frac{1}{2}$ Solution: Problem: $ \frac{1}{4} + \frac{1}{16} + \frac{1}{64} + \dots = \frac{1}{3}$ Solution: Problem: $ 1 + r + r^2 + \dots = \frac{1}{1-r}$ if $ r < 1$. Solution: This last one follows from similarity of the subsequent trapezoids: the right edge of the teal(ish) trapezoid has length $ r$, a..
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Problem: $ \frac{1}{2} + \frac{1}{4} + \frac{1}{8} + \dots = 1$ Solution: Problem: $ \frac{1}{3} + \frac{1}{9} + \frac{1}{27} + \dots = \frac{1}{2}$ Solution: Problem: $ \frac{1}{4} + \frac{1}{16} + \frac{1}{64} + \dots = \frac{1}{3}$ Solution: Problem: $ 1 + r + r^2 + \dots = \frac{1}{1-r}$ if $ r < 1$. Solution: This last one follows from similarity of the subsequent trapezoids: the right edge of the teal(ish) trapezoid has length $ r$, a..
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Problem: $ \frac{1}{2} + \frac{1}{4} + \frac{1}{8} + \dots = 1$ Solution: Problem: $ \frac{1}{3} + \frac{1}{9} + \frac{1}{27} + \dots = \frac{1}{2}$ Solution: Problem: $ \frac{1}{4} + \frac{1}{16} + \frac{1}{64} + \dots = \frac{1}{3}$ Solution: Problem: $ 1 + r + r^2 + \dots = \frac{1}{1-r}$ if $ r < 1$. Solution: This last one follows from similarity of the subsequent trapezoids: the right edge of the teal(ish) trapezoid has length $ r$, a..
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I just updated this blog to wordpress 3.2 which came out this week. Only a small glitch caused by me running an old theme which wasn’t 100% compatible. WordPress itself seems to be better. I had a quick look at the Twenty Eleven theme which comes packaged with wordpress and it looks nice even via … Continue reading July Update
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So after a fairly lengthy period of inattention to my Linkzie bookmark manager, I got frustrated on my current project and turned my focus to Linkzie today for some updates. There's a new menu bar shamelessly stolen from the new google bar. A brand new "beach house" color theme has been applied. The "organize" UI has been changed significantly. Lots of other minor UX tweaks have been made. For example, you can now click anywhere on the en....
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The SharePoint permission model uses user impersonation, where a typical asp.net application will run under the permissions of the…
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Jakob Nielsen recently published this post, where he (and I guess his team) analyze why the Wall Street Journal mobile app gets such bad customer reviews. It all stems from a horrible interface where the customers are led to believe that they need to pay separately for the monthly subscription to to the mobile app, when in fact it's free for existing subscribers.
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MySQL turns out to be a good Swiss Army Knife for persistence, if used wisely. Understanding disk access patterns driven by your storage…
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Jakob Nielsen recently published this post, where he (and I guess his team) analyze why the Wall Street Journal mobile app gets such bad customer reviews. It all stems from a horrible interface where the customers are led to believe that they need to pay separately for the monthly subscription to to the mobile app, when in fact it's free for existing subscribers.
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MySQL turns out to be a good Swiss Army Knife for persistence, if used wisely. Understanding disk access patterns driven by your storage…
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We assume the reader is familiar with the concepts of determinism and finite automata, or has read the corresponding primer on this blog. The Mother of All Computers Last time we saw some models for computation, and saw in turn how limited they were. Now, we open Pandrora’s hard drive: Definition: A Turing machine is a tuple $ (S, \Gamma, \Sigma, s_0, F, \tau)$, where $ S$ is a set of states, $ \Gamma$ is a set of tape symbols, including a ..
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We assume the reader is familiar with the concepts of determinism and finite automata, or has read the corresponding primer on this blog. The Mother of All Computers Last time we saw some models for computation, and saw in turn how limited they were. Now, we open Pandrora’s hard drive: Definition: A Turing machine is a tuple $ (S, \Gamma, \Sigma, s_0, F, \tau)$, where $ S$ is a set of states, $ \Gamma$ is a set of tape symbols, including a ..
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We assume the reader is familiar with the concepts of determinism and finite automata, or has read the corresponding primer on this blog. The Mother of All Computers Last time we saw some models for computation, and saw in turn how limited they were. Now, we open Pandrora’s hard drive: Definition: A Turing machine is a tuple $ (S, \Gamma, \Sigma, s_0, F, \tau)$, where $ S$ is a set of states, $ \Gamma$ is a set of tape symbols, including a ..
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I have noticed that many people don’t know what a blog is, so I would like to talk about that briefly. A blog is a type of website or part of a website. Blogs are usually maintained by an individual with regular entries. (…) Entries are commonly displayed in reverse-chronological order. Blog can also be used as a verb, meaning to maintain or add content to a blog. Source: Wikipedia A blog is a website. A blog has many entries or..
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I have noticed that many people don’t know what a blog is, so I would like to talk about that briefly. A blog is a type of website or part of a website. Blogs are usually maintained by an individual with regular entries. (…) Entries are commonly displayed in reverse-chronological order. Blog can also be used as a verb, meaning to maintain or add content to a blog. Source: Wikipedia A blog is a website. A blog has many entries or..
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I saw this article on Hacker News today. It's very similar to a blog post I was planning to write, but never did.
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I saw this article on Hacker News today. It's very similar to a blog post I was planning to write, but never did.
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The first step in studying the sorts of possible computations (and more interestingly, those things which cannot be computed) is to define exactly what we mean by a “computation.” At a high level, this is easy: a computation is simply a function. Given some input, produce the appropriate output. Unfortunately this is much too general. For instance, we could define almost anything we want in terms of functions. Let $ f$ be the function which..
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The first step in studying the sorts of possible computations (and more interestingly, those things which cannot be computed) is to define exactly what we mean by a “computation.” At a high level, this is easy: a computation is simply a function. Given some input, produce the appropriate output. Unfortunately this is much too general. For instance, we could define almost anything we want in terms of functions. Let $ f$ be the function which..
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The first step in studying the sorts of possible computations (and more interestingly, those things which cannot be computed) is to define exactly what we mean by a “computation.” At a high level, this is easy: a computation is simply a function. Given some input, produce the appropriate output. Unfortunately this is much too general. For instance, we could define almost anything we want in terms of functions. Let $ f$ be the function which..
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Check out my new little automation utility belt app for the keyboard-centric power users. It is hosted on a github project here .
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Problem: Prove that for all $ n,k \in \mathbb{N}, k > 1$, we have $$\sum \limits_{i=0}^{n} k^i = \frac{k^{n+1}-1}{k-1}$$ Solution: Representing the numbers in base $ k$, we have that each term of the sum is all 0’s except for a 1 in the $ i$th place. Hence, the sum of all terms is the $ n$-digit number comprised of all 1’s. Multiplying by $ k-1$ gives us the $ n$-digit number where every digit is $ k-1$.
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Problem: Prove that for all $ n,k \in \mathbb{N}, k > 1$, we have $$\sum \limits_{i=0}^{n} k^i = \frac{k^{n+1}-1}{k-1}$$ Solution: Representing the numbers in base $ k$, we have that each term of the sum is all 0’s except for a 1 in the $ i$th place. Hence, the sum of all terms is the $ n$-digit number comprised of all 1’s. Multiplying by $ k-1$ gives us the $ n$-digit number where every digit is $ k-1$.
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Problem: Prove that for all $ n,k \in \mathbb{N}, k > 1$, we have $$\sum \limits_{i=0}^{n} k^i = \frac{k^{n+1}-1}{k-1}$$ Solution: Representing the numbers in base $ k$, we have that each term of the sum is all 0’s except for a 1 in the $ i$th place. Hence, the sum of all terms is the $ n$-digit number comprised of all 1’s. Multiplying by $ k-1$ gives us the $ n$-digit number where every digit is $ k-1$.
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