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What exactly are “spin-locks”?
...ritical sections etc), operating system puts your thread in the WAIT state and preempts it by scheduling other threads on the same core. This has a performance penalty if the wait time is really short, because your thread now has to wait for a preemption to receive CPU time again.
Besides, kernel ob...
What's wrong with foreign keys?
...ber correctly). However, to me they seem pretty vital to avoid duplication and subsequent data integrity problems throughout your database.
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How do I see what character set a MySQL database / table / column is?
...ER_SET_APPLICABILITY` CCSA
WHERE CCSA.collation_name = T.table_collation
AND T.table_schema = "schemaname"
AND T.table_name = "tablename";
For Columns:
SELECT character_set_name FROM information_schema.`COLUMNS`
WHERE table_schema = "schemaname"
AND table_name = "tablename"
AND column_na...
Is there a way to keep Hudson / Jenkins configuration files in source control?
I am new to Hudson / Jenkins and was wondering if there is a way to check in Hudson's configuration files to source control.
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Is it possible for a computer to “learn” a regular expression by user-provided examples?
...ton, it is possible to learn some regular expressions by a program. Kearns and Valiant show some cases where it is not possible to learn a finite automaton. A related problem is learning hidden Markov Models, which are probabilistic automata that can describe a character sequence. Note that most mod...
Postgres: SQL to list table foreign keys
...to list all foreign keys for a given table? I know the table name / schema and I can plug that in.
23 Answers
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Connection timeout for SQL server
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Yes, you could append ;Connection Timeout=30 to your connection string and specify the value you wish.
The timeout value set in the Connection Timeout property is a time expressed in seconds. If this property isn't set, the timeout value for the connection is the default value (15 seconds).
Mo...
Drop unused factor levels in a subsetted data frame
...t, so the mydf <- droplevels(mydf) solution suggested by Roman Luštrik and Tommy O'Dell below is preferable.
– Johan
May 9 '14 at 10:41
1
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How to code a BAT file to always run as admin mode?
...se the quotes even if they are not needed, though.
– Andriy M
Jul 25 '11 at 4:38
18
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How do I partially update an object in MongoDB so the new object will overlay / merge with the exist
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If I understand the question correctly, you want to update a document with the contents of another document, but only the fields that are not already present, and completely ignore the fields that are already set (even if to another valu...