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Quickly reading very large tables as dataframes
...
# sqldf as on SO
f <- file("test.csv")
system.time(SQLf <- sqldf("select * from f", dbname = tempfile(), file.format = list(header = T, row.names = F)))
## user system elapsed
## 10.21 0.47 10.73
ff / ffdf
require(ff)
system.time(FFDF <- read.csv.ffdf(file="test.csv",nro...
LR性能指标解释 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...。
4.JMap。监控java程序是否有内存泄漏，需要配合eclipse插件或者MemoryAnalyzer来使用。
5.JProfiler。全面监控每个节点的CPU使用率、内存使用率、响应时间累计值、线程执行情况等，需要在JVM参数中进行配置。
6.Nmon。全面监控linux...
How do I put double quotes in a string in vba?
...ring
Dim objDataObj As Object
'\Check that single cell is selected!
If Selection.Cells.Count > 1 Then
MsgBox "Select single cell only!", vbCritical
Exit Sub
End If
'Check if we are not on a blank cell!
If Len(ActiveCell.Formu...
How do I see active SQL Server connections?
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when you have to filter for specific db selecting from sys.sysprocesses is better
– Iman
Dec 2 '13 at 4:29
2
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How do I remove a project configuration in Visual Studio 2008?
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In the Configuration Manager, select "Edit..." in the "Configuration" column for each project (not via the dropdown named Active solution configuration) that has configurations you want to remove.
In the dialog that pops up, mark each unwanted configurat...
What exactly is nullptr?
...rloading a function for both pointers and integers, and passing nullptr to select the pointer version. Passing NULL or 0 would confusingly select the int version.
A cast of nullptr_t to an integral type needs a reinterpret_cast, and has the same semantics as a cast of (void*)0 to an integral type (...
SQL: deleting tables with prefix
...r you:
In the MySQL shell or through PHPMyAdmin, use the following query
SELECT CONCAT( 'DROP TABLE ', GROUP_CONCAT(table_name) , ';' )
AS statement FROM information_schema.tables
WHERE table_name LIKE 'myprefix_%';
This will generate a DROP statement which you can than copy and execut...
Unique random string generation
...ncat(
Enumerable
.Repeat(0, int.MaxValue)
.Select(e => RandomByte())
.Where(randomByte => randomByte < outOfRange)
.Take(length)
.Select(randomByte => alphabet[randomByte % alphabet.Length])
);
}
byte RandomByte()
{...
Print all but the first three columns
...ents. We have asked the OP to choose a more correct answer, and he/she has selected mine. After some other contributors have edited my answer to reference there answer (see the history). Is it clear for you? What do you advice me to improve the understandability of my answer? Cheers ;-)
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How to group time by hour or by 10 minutes
...time intervals. (There is no collision between years.)
Including it in the SELECT statement will give your output a column with pretty output truncated at the level you specify.
'2000' is an "anchor date" around which SQL will perform the date math. Jereonh discovered below that you encounter an in...