Multiplex leveldowns--accessing values from multiple stores through one
npm install easier-level-multiplexerMultiplex a single leveldown compatible store to many, determining which store will have a copy of the value based on some mapper function which utilizes the value.
Is similar but slightly more versitile than level-mount as instead of depending on the key, it enables you to sort based on the value. This however results in more
overhead because you have to save pointers to the values in the multiplexed stores.
Fortunately this project supports singular values existing in multiple backend stores (replication), it also abuses the easier-leveldown post method enabling the
put keys of the level-multiplexer to be completely independent of the keys in the replicated stores (which are obtained via a post).
Example:
``jsstores
const hybrid_db = levelup(levelmount({
store: leveldown('root'),
options: {}, // options for leveldown open
stores: [
{
key: 'fallback',
store: memdown(),
},
{
key: 'a',
store: memdown(),
},
{
key: 'b',
store: someotherdown(),
options: {}, // someotherdown options for leveldown open
}
],
// We'll map based on a variable which takes a list
mapper: (v) => {
const stores = v.stores.filter((store) => ['a', 'b'].indexOf(store))
if (stores.length === 0)
return ['fallback']
return stores
}
})
hybrid_db.put('hello', { stores: ['a', 'b'], doc: 'whatever' }) // ends up in stores a and b with an arbitrarily generated keys for eachfallback
hybrid_db.put('goodbye', { stores: [], doc: 'whatever' }) // ends up in store with an arbitrarily generated key
hybrid_db.get('hello') // fetches the document versions back from the a and b, potentially dealing with collisions`
It also supports the features of easier-abstract-leveldown, including post, propagation of changes` from underlying easier leveldowns.