大约有 42,000 项符合查询结果（耗时：0.0613秒） [XML]
E11000 duplicate key error index in mongodb mongoose
...nt with the sparse index to filter these null values from the unique index and avoid the error.
unique indexes
Sparse indexes only contain entries for documents that have the indexed field, even if the index field contains a null value.
In other words, a sparse index is ok with multiple documents...
Program only crashes as release build — how to debug?
...t a program nonetheless) is crashing, but only when built in release mode, and only when launched from the command line. Through caveman debugging (ie, nasty printf() messages all over the place), I have determined the test method where the code is crashing, though unfortunately the actual crash se...
powershell - extract file name and extension
I need to extract file name and extension from e.g. my.file.xlsx. I don't know the name of file or extension and there may be more dots in the name, so I need to search the string from the right and when I find first dot (or last from the left), extract the part on the right side and the part on the...
.keyCode vs. .which
... The answer below was written in 2010. Here many years later, both keyCode and which are deprecated in favor of key (for the logical key) and code (for the physical placement of the key). But note that IE doesn't support code, and its support for key is based on an older version of the spec so isn't...
Plain Old CLR Object vs Data Transfer Object
...POCO follows the rules of OOP. It should (but doesn't have to) have state and behavior. POCO comes from POJO, coined by Martin Fowler [anecdote here]. He used the term POJO as a way to make it more sexy to reject the framework heavy EJB implementations. POCO should be used in the same context in...
How can I unit test Arduino code?
...Sim-based tests
There's a lot of discussion about what unit test means and I'm not
really trying to make an argument about that here. This post is not
telling you to avoid all practical testing on your ultimate target
hardware. I am trying to make a point about optimizing your
developmen...
What's the syntax for mod in java
...
Careful with the terms mod and modular because n (mod m) IS ALWAYS >= 0 but not n % m. n % m is in the range > -m and < m. Although Java has a remainder operator for int and long types, it has no modulus function or operator. I.e., -12 % 10 = ...
How to get script of SQL Server data? [duplicate]
...us to the MySQL dump from SQL Server. I need to be able to pick the tables and export the schema and the data (or I can export the schema via SQL Server Management Studio and export the data separately somehow).
...
Where should signal handlers live in a django project?
...started implementing signal listeners in a django project. While I understand what they are and how to use them. I am having a hard time figuring out where I should put them. The documentation from the django site has this to say:
...
Confusion between factor levels and factor labels
There seems to be a difference between levels and labels of a factor in R.
Up to now, I always thought that levels were the 'real' name of factor levels, and labels were the names used for output (such as tables and plots). Obviously, this is not the case, as the following example shows:
...