Comment by otterley

3 months ago

My mistake. Doesn’t it have a global lock though?

Also, even if LMDB supports databases larger than RAM, that’s it doesn’t mean it’s a good idea to have a working set that exceeds that size. Unless you’re claiming it’s scan resistant?

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otterley

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hyc_symas  3 months ago

It has a single writer transaction mutex, yes. But it's a process-shared mutex, so it will serialize write transactions across an arbitrary number of processes. And of course, read transactions are completely lockfree/waitfree across arbitrarily many processes.

As for working set size, that is always merely the height of the B+tree. Scans won't change that. It will always be far more efficient than any other DB under the same conditions.

  • otterley  3 months ago

    > As for working set size, that is always merely the height of the B+tree.

    This statement makes no sense to me. Are you using a different definition of "working set" than the rest of us? A working set size is application and access pattern dependent.

    > It will always be far more efficient than any other DB under the same conditions

    That depends on how broadly or narrowly one defines "same conditions" :-)