thanks for your answer , helpfull Le mardi 19 juillet 2016 11:19:22 UTC+2, Simran Brucherseifer a écrit : > > Hey gui, > > ArangoDB is mostly-memory. All indexes (except for the type "persistent") > are kept in memory and need to rebuilt on restart. This means the indexes > need to fit into the main memory, otherwise the operating system will start > to swap and performance degrades. There has to be free memory for > (partially) loading collections and to construct query results as well. > > The data is persisted to mass storage (disk / flash drive). By default, it > doesn't wait until the data is fully synced. There is an optional > waitForSync parameter to forcefully wait for synchronization, which can be > set per collection and query. It will decrease performance depending on how > fast your mass storage is, but gives you additional security (e.g. for > banking transactions). > > If you don't want the data to be synced at all, you may create a volatile > collection. The collection itself will survive unloads and restarts, but > the data will be kept in-memory only and be lost on these events. You can > use the isVolatile option to use certain collections as cache, i.e. for > data that can easily be computed again after a restart and syncing it to > disk would only slow things down (performance gain). > > To use ArangoDB as key/value store means to use the default primary index > only, a lookup by (hash) key. The values you store are always (JSON) > documents. They can be arbitrarily structured. You may define secondary > indexes on certain attributes, but it then no longer classifies as > key/value store, but document store (the extra indexes have to look at the > value-part, which means it is no longer treated opaque). > > There are no bitwise operations, but if you really require them, they can > be easily added using AQL user-defined functions. I would like to hear what > you would like to use them for. >
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