Contents
Memory-mapped files can be shared across multiple processes. Processes can map to the same memory-mapped file by using a common name that is assigned by the process that created the file. To work with a memory-mapped file, you must create a view of the entire memory-mapped file or a part of it.
How to store multiple values in single column?
It is normalised, and will be much easier to query. Will allow you to query for all users with a particular role, such as SELECT user_id, user.name FROM user_role JOIN user WHERE role=’Admin’ rather than having to use string parsing to get details out of a column.
How to store a database in memory in EF Core?
First off, we need to write a class that inherits from DbContext (which allows us to query the datastore) and a data generator which will create some sample data. Here’s the code for our BoardGamesDbContext class: Because this database will be stored in memory, we require some sample data with which the database can be populated.
How to create sample data for our memory database?
The simplest way to create sample data for our memory “database” is to inject the data into said database on application startup. To do that, our new class (which I called DataGenerator) will need to search the Services layer for the context and use it to insert new board games into our “database”.
To check the size of the shared memory file system, enter the following command: df –k /dev/shm
Is the section object based on a file on disk?
Note that the section object might be based on a file on disk, in which case you have a memory-mapped file shared across processes: this is what the OS image loader does with DLLs. Or, the section object may not be based on a file on disk, in which case it is purely a shared memory region backed by the page file, if present.
Varnish appears to use a plain memory-mapped file for its shared memory (instead of, e.g., POSIX shm_open ). From the source: On BSD, MAP_NOSYNC requests that the kernel not write the shared data to disk unless forced (e.g., to free up memory). When it’s mlocked as well, that should almost never happen.