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Is it okay to say that monetdDB is an in-memory database. I read Here that its use array as data storage in memory to perform relational algebra operation. Is it enough to say it is an in-memory database ?

Fopa Léon Constantin
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1 Answers1

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MonetDB is not an in memory database.

You confuse "memory-mapped file array" with "in-memory array".

When using memory-mapped file, one can do direct mapping (array) structure data in memory on disk.

If some records queried with SQL, it will be mapped to a mmap file, and then loaded to memory by OS's kernel.

When that records not used any more, it's memory space will be reclaimed by the OS's kernel.

This is how virtual memory management work.

Iwanio
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    This logic seems flawed to me. Even when allocating memory using malloc, the OS can decide to swap out that memory region if swapping is enabled. Does that mean a system with activated swap can never run an in-memory database? – Holger Apr 05 '15 at 01:47