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Locking a file in Python
I need to lock a file for writing in Python. It will be accessed from multiple Python processes at once. I have found some solutions online, but most fail for my purposes as they are often only Unix based or Windows based.
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Inserting data into a temporary table
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INSERT INTO #TempTable (ID, Date, Name)
SELECT id, date, name
FROM physical_table
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SQL Joins Vs SQL Subqueries (Performance)?
...vary. The speed will depend a lot on indexes (do you have indexes on both ID columns? That will help a lot...) among other things.
The only REAL way to tell with 100% certainty which is faster is to turn on performance tracking (IO Statistics is especially useful) and run them both. Make sure to...
How to read a large file line by line?
I want to read a file line by line, but without completely loading it in memory.
14 Answers
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Difference between modes a, a+, w, w+, and r+ in built-in open function?
...s (Additional characters may follow these sequences.):
``r'' Open text file for reading. The stream is positioned at the
beginning of the file.
``r+'' Open for reading and writing. The stream is positioned at the
beginning of the file.
``w'' Truncate file to zero lengt...
How to check if a folder exists
... with the new Java 7 IO features, actually I trying to receive all the xml files of a folder. But this throws an exception when the folder does not exist, how can I check if the folder exists with the new IO?
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Get size of folder or file
How can I retrieve size of folder or file in Java?
18 Answers
18
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postgresql: INSERT INTO … (SELECT * …)
...te database and fetch result. For example:
psql dbtest
CREATE TABLE tblB (id serial, time integer);
INSERT INTO tblB (time) VALUES (5000), (2000);
psql postgres
CREATE TABLE tblA (id serial, time integer);
INSERT INTO tblA
SELECT id, time
FROM dblink('dbname=dbtest', 'SELECT id, time FRO...
Is null reference possible?
...r, which may not be possible to do. Consider this simple function inside a file converter.cpp:
int& toReference(int* pointer) {
return *pointer;
}
When the compiler sees this function, it does not know whether the pointer is a null pointer or not. So it just generates code that turns any po...
find() with nil when there are no records
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Yes, just do:
Challenge.find_by_id(10)
For Rails 4 and 5:
Challenge.find_by(id: 10)
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