There's no synchronous open at this time. This has been an issue a couple of
times when porting apps to Medea as most Node database libraries use
synchronous database initialization by default.
Adding db.openSync is more time-consuming work than you may think. There's a
lot going on when you open a new Medea database. It's the most expensive
operation, because it:
1) checks for a directory (creates if necessary)
2) opens a new data file for writing
3) opens a new hint file for writing
4) creates a lock file
5) writes the pid to the lock file
6) scans existing files
7) loads key to file ID and offset mappings from each file into memory
To create a sync version of all that means creating *Sync methods all over the
place. I don't think this will be something we introduce in v1.
For servers, I usually….
db.open(function() {
server.listen(process.env.PORT || 3000);
});
--
Kevin Swiber
@kevinswiber
https://github.com/kevinswiber
On Apr 19, 2013, at 11:45 AM, Angelo Chen <[email protected]> wrote:
> Hi Kevin,
>
> just tried, got a question, is there a way to open() at beginning,
> then use it later? the sample is, you have to put the code in a
> callback, this does not work:
>
> ar Medea = require('medea');
>
> var medea = new Medea();
> medea.open()
>
> medea.get('hello', function(err, val) {
> console.log(val.toString());
> medea.close();
> });
>
>
>
> On 4月19日, 下午11时10分, Kevin Swiber <[email protected]> wrote:
>> Angelo,
>>
>> Not at this time. Implementing a browser shouldn't be too difficult,
>> though. Medea stores both keys and values as Buffer objects. You could
>> iterate through the key-value store and stringify key and value Buffers
>> prior to display.
>>
>> There are a number of Web front-end data grids you could use for the UI.
>>
>> --
>> Kevin Swiber
>> @kevinswiberhttps://github.com/kevinswiber
>>
>> On Apr 19, 2013, at 10:52 AM, Angelo Chen <[email protected]> wrote:
>>
>>
>>
>>
>>
>>
>>
>>> Hi Kevin,
>>
>>> I took a look, the 100% js codebase is one plus factor, one thing, is
>>> there any utility to browse the database?
>>
>>> Thanks,
>>
>>> Angelo
>>
>>> On 4月19日, 下午8时03分, Kevin Swiber <[email protected]> wrote:
>>>> On Apr 19, 2013, at 4:59 AM, Angelo Chen <[email protected]> wrote:
>>
>>>>> Hi,
>>
>>>>> What are the options for embedded database? I use redis and mongodb for
>>>>> now, but sometimes you made some small apps, and does not want to mix
>>>>> data with existing redis db or mongodb. it should be easier to install,
>>>>> now I'm looking at nosql,https://npmjs.org/package/nosql, also
>>>>> ejdb,https://npmjs.org/package/ejdb, but seems you can not have your own
>>>>> data file for a individual app. sqllite is another, but it's not json
>>>>> based, any suggestions? Thanks,
>>
>>>>> Angelo
>>
>>>> Hey Angelo,
>>
>>>> I'm working on an a persistent key-value store in Node right now. It's
>>>> called Medea, and it's currently 100% JavaScript.
>>
>>>> https://github.com/argo/medea
>>
>>>> It's pre-1.0 at this time, but I think the API is pretty stable.
>>
>>>> Julian Gruber maintains a benchmark of databases/libraries called from
>>>> Node. You can find that
>>>> here:https://github.com/juliangruber/multilevel-bench
>>
>>>> Medea (10.000x)
>>>> 12,324 op/s ⨠ set small
>>>> 12,313 op/s ⨠ set medium
>>>> 12,248 op/s ⨠ set large
>>>> 40,566 op/s ⨠ get large
>>>> 44,246 op/s ⨠ get medium
>>>> 45,174 op/s ⨠ get small
>>
>>>> levelUP (10.000x)
>>>> 38,374 op/s ⨠ set small
>>>> 33,019 op/s ⨠ set medium
>>>> 23,348 op/s ⨠ set large
>>>> 30,622 op/s ⨠ get large
>>>> 36,191 op/s ⨠ get medium
>>>> 38,326 op/s ⨠ get small
>>
>>>> This is using an earlier version of Medea. The "set" numbers for Medea
>>>> are a lot better now than they were at that time, though I believe levelUP
>>>> is still doing faster writes.
>>
>>>> LevelUP (and LevelDB) have a few differences. In Medea, a range query
>>>> would have to be built from the calling code. You'd have to filter
>>>> listKeys() and then iterate over those keys doing a get on each one.
>>
>>>> Medea keeps a copy of all keys and value file IDs/offsets in-memory (to
>>>> make a maximum of 1 disk seek per get), so your key set has to fit in
>>>> memory.
>>
>>>> It's working pretty good for me, and I know at least one other person who
>>>> is using it for their project.
>>
>>>> Medea is pretty stable now, but I expect stability issues to be raised and
>>>> squelched as we approach 1.0.
>>
>>>> That said, levelUP and LevelDB are great projects, and you can't go wrong
>>>> with those options, either. Medea being all-JavaScript is a pro for me at
>>>> this time.
>>
>>>> Cheers,
>>
>>>> --
>>>> Kevin Swiber
>>>> @kevinswiberhttps://github.com/kevinswiber
>>
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