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postgresql COUNT(DISTINCT …) very slow
...
You can use this:
SELECT COUNT(*) FROM (SELECT DISTINCT column_name FROM table_name) AS temp;
This is much faster than:
COUNT(DISTINCT column_name)
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Is it better to reuse a StringBuilder in a loop?
...-time );
}
}
Results:
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Note that this is with JRE 1.6.0_07.
Based on Jon Skeet's ideas in the edit, here's version 2. Same results though.
public class ScratchPad {
static String a;
public static void main( String[] args ) throws Exception {
long time = Syst...
How to stop a JavaScript for loop?
... is a good approach. Thanks @T.J. Crowder
– techloris_109
Sep 13 '17 at 7:35
@T.J. Crowder which statement is a good a...
How to access a preexisting collection with Mongoose?
...ctions of UserSchema and I want to give each one a different name Eg: users_server1, users_server2, users_server3...
– Ragnar
Jun 6 '14 at 20:41
1
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How can I efficiently download a large file using Go?
....Errorf("bad status: %s", resp.Status)
}
// Writer the body to file
_, err = io.Copy(out, resp.Body)
if err != nil {
return err
}
return nil
}
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Rendering JSON in controller
...ting your own dogfood and doing both
In both cases render :json => some_data will JSON-ify the provided data. The :callback key in the second example needs a bit more explaining (see below), but it is another variation on the same idea (returning data in a way that JavaScript can easily handle....
What is the appropriate HTTP status code response for a general unsuccessful request (not an error)?
...per has exceeded the daily limit on requests.
And indeed they do:
PAYMENT_REQUIRED (402)
A daily budget limit set by the developer has been reached.
The requested operation requires more resources than the quota allows. Payment is required to complete the operation.
The requested operation requir...
Efficient SQL test query or validation query that will work across all (or most) databases
...himpsky)
PostgreSQL
SQLite
SELECT 1 FROM DUAL
Oracle
SELECT 1 FROM any_existing_table WHERE 1=0
or
SELECT 1 FROM INFORMATION_SCHEMA.SYSTEM_USERS
or
CALL NOW()
HSQLDB (tested with version 1.8.0.10)
Note: I tried using a WHERE 1=0 clause on the second query, but it didn't work as a value for Ap...
Rails find_or_create_by more than one attribute?
There is a handy dynamic attribute in active-record called find_or_create_by:
5 Answers
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How to form tuple column from two columns in Pandas
...rtable with zip. It comes in handy when dealing with column data.
df['new_col'] = list(zip(df.lat, df.long))
It's less complicated and faster than using apply or map. Something like np.dstack is twice as fast as zip, but wouldn't give you tuples.
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