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SQL Server等待事件—PAGEIOLATCH_EX

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什么是 PAGEIOLATCH_EX 等待事件？下面我们将对 PAGEIOLATCH_EX 等待事件的相关资料做一个简单的归纳、整理。关于 PAGEIOLATCH_EX ，官方文档的简单介绍如下： PAGEIOLATCH_EX ： Occurs when a task is waiting on a latch for a buffer that is in an I/O request. The latch request is in Exclusive mode. Long waits may indicate problems with the disk subsystem. 在任务等待 I/O 请求中缓冲区的闩锁时发生。闩锁请求处于 “ 独占 ” 模式。长时间的等待可能指示磁盘子系统出现问题。 In SQL Server, a latch is a short-term lightweight synchronization object. Buffer latches including the PAGEIOLATCH_EX wait type are used to synchronize access to BUF structures and associated pages in the SQL Server database. The most

Removing rows containing specific dates in R

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问题 Disclaimer: I am going to come out of this looking silly. I have a data frame containing a column which has a date of class POSIXct . I am trying to remove some of the rows containing specific dates- public holidays. I tried to do that using this: > modelset.nonholiday <- modelset[!modelset$date == as.POSIXct("2013-12-31")| !modelset$date ==as.POSIXct("2013-07-04") | !modelset$date == as.POSIXct("2014-07-04")| !modelset$date == as.POSIXct ("2013-11-28") | !modelset$date == as.POSIXct ("2013

Removing rows containing specific dates in R

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Extract rows with highest and lowest values from a data frame

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问题 I'm quite new to R, I use it mainly for visualising statistics using ggplot2 library. Now I have faced a problem with data preparation. I need to write a function, that will remove some number (2, 5 or 10) rows from a data frame that have highest and lowest values in specified column and put them into another data frame, and do this for each combination of two factors (in my case: for each day and server). Up to this point, I have done the following steps (MWE using esoph example dataset). I

R How to group_by, split or subset by row values

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问题 This is continued from last question R, how to group by row value? Split? The change in input Dataframe is id = str_c("x",1:22) val = c(rep("NO1", 2), "START", rep("yes1", 2), "STOP", "NO", "START","NO1", "START", rep("yes2", 3), "STOP", "NO1", "START", rep("NO3",3), "STOP", "NO1", "STOP") data = data.frame(id,val) Expected output is dataframe with val column as follows- val = c("START", rep("yes1", 2), "STOP", "START","NO1", "START", rep("yes2", 3), "STOP", "START", rep("NO3",3), "STOP",

Find values that are between list of numbers

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问题 I have two list of numbers like below. x <- c(1, 5, 10, 17, 21, 30) y <- c(2, 7, 19) In my dataset, x divides 1 to 30 in different segments (from 1-5, 5-10, 10-17, 17-21, 21-30). Would it be possible to match these segments to numbers in y ? (In this case, I'd want to get c(1,5,17) as an output because 2 is between 1 and 5, 7 is between 5 and 10, and 19 is in between 17 and 21.) 回答1: You can do this with sapply and a simple function sapply(y, function(a) x[max(which(x<a))]) [1] 1 5 17 回答2:

[LeetCode] 1090. Largest Values From Labels

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使用 Java 爬取 LeetCode 题目内容以及提交的AC代码传送门 Description We have a set of items: the i -th item has value values[i] and label labels[i] . Then, we choose a subset S of these items, such that: |S| <= num_wanted For every label L , the number of items in S with label L is <= use_limit . Return the largest possible sum of the subset S . Example 1: Input: values = [5,4,3,2,1], labels = [1,1,2,2,3], num_wanted = 3, use_limit = 1 Output: 9 Explanation: The subset chosen is the first, third, and fifth item. Example 2: Input: values = [5,4,3,2,1], labels = [1,3,3,3,2], num_wanted = 3, use_limit = 2 Output:

How to filter rows based on the previous row and keep previous row using dplyr?

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问题 I am trying to subset rows of a data set using a condition that's based on the previous row, whilst keeping the previous row in the subsetted data. This is essentially the same as the question here, but I am looking for a dplyr approach: Select specific rows based on previous row value (in the same column) I have taken the dplyr approach applied in the comments to that answer, but I am unable to figure out the last step of retaining the previous row. I can get the rows that support the

How to use a loop to delete all rows with negative values in R

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问题 I am new to loops. I have an unwieldy data frame that I want to cut down so that only observations (rows) without negative numbers remain. Here is where I'm stuck. This creates a null value every time instead of a trimmed down data frame. mydata=for (i in names(df)) { subset(df, df[[ paste(i)]]>=0) } 回答1: How about a purely vectorised solution: DF[!rowSums(DF < 0), ] # ID Items Sequence #1 1 D 1 #2 1 A 2 #5 2 B 2 Data DF=structure(list(ID = c(1, 1, 1, -1, 2), Items = c("D", "A", "A", "A", "B"

Return values with matching conditions in r

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问题 I would like to return values with matching conditions in another column based on a cut score criterion. If the cut scores are not available in the variable, I would like to grab closest larger value. Here is a snapshot of dataset: ids <- c(1,2,3,4,5,6,7,8,9,10) scores.a <- c(512,531,541,555,562,565,570,572,573,588) scores.b <- c(12,13,14,15,16,17,18,19,20,21) data <- data.frame(ids, scores.a, scores.b) > data ids scores.a scores.b 1 1 512 12 2 2 531 13 3 3 541 14 4 4 555 15 5 5 562 16 6 6