Indexing array values in an object in an IndexedDB

Question

For a Chrome app, which stores data in IndexedDB, I have an object like this:

var simplifiedOrderObject = {
    "ordernumber": "123-12345-234",
    "name": "Mr. Sample",
    "address": "Foostreet 12, 12345 Bar York",
    "orderitems": [
        {
            "item": "brush",
            "price": "2.00"
        },
        {
            "item": "phone",
            "price": "30.90"
        }
    ],
    "parcels": [
        {
            "service": "DHL",
            "track": "12345"
        },
        {
            "service": "UPS",
            "track": "3254231514"
        }
    ]
}

If I store the hole object in an objectStore, can I use an index for "track", which can be contained multiple times in each order object?

Or is it needed or possibly better/faster to split each object into multiple objectStores like know from relational DBs:

order
orderitem
parcel

The solution should also work in a fast way with 100.000 or more objects stored.

Lutz · Accepted Answer · 2016-05-05 17:09:09Z

11

Answering my own question: I have made some tests now. It looks like it is not possible to do this with that object in only 1 objectStore.

An other example object which would work:

var myObject = {
    "ordernumber": "123-12345-234",
    "name": "Mr. Sample",
    "shipping": {"method": "letter",
                 "company": "Deutsche Post AG" }
}

Creating an index will be done by:

objectStore.createIndex(objectIndexName, objectKeypath, optionalObjectParameters);

With setting objectKeypath it is possible to address a value in the main object like "name":

objectStore.createIndex("name", "name", {unique: false});

It would also be possible to address a value form a subobject of an object like "shipping.method":

objectStore.createIndex("shipping", "shipping.method", {unique: false});

BUT it is not possible to address values like the ones of "track", which are contained in objects, stored in an array. Even something like "parcels[0].track" to get the first value as index does not work.

Anyhow, it would be possible to index all simple elements of an array (but not objects).

So the following more simple structure would allow to create an index entry for each parcelnumber in the array "trackingNumbers":

var simplifiedOrderObject = {
    "ordernumber": "123-12345-234",
    "name": "Mr. Sample",
    "address": "Foostreet 12, 12345 Bar York",
    "orderitems": [
        {
            "item": "brush",
            "price": "2.00"
        },
        {
            "item": "phone",
            "price": "30.90"
        }
    ],
    "trackingNumbers": ["12345", "3254231514"]
}

when creating the index with multiEntry set to true:

objectStore.createIndex("tracking", "trackingNumbers", {unique: false, multiEntry: true});

Anyhow, the missing of the possibility to index object values in arrays, makes using indexedDB really unneeded complicated. It's a failure in design. This forces the developer to do things like in relational DBs, while lacking all the possibilities of SQL. Really bad :(

edited May 5, 2016 at 17:09

answered Apr 28, 2016 at 22:23

Lutz

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4 Comments

Joshua Bell Over a year ago

You are correct - the current Indexed DB API doesn't make this easy. I have a tracking bug for this issue here: github.com/w3c/IndexedDB/issues/35

Lutz Over a year ago

i would say this is no bug, because it works like it is written in the specification. But it is really a missing feature... :(

Joshua Bell Over a year ago

Yeah, "issue" not "bug". BTW, I'm the editor of the specification. :)

Lutz Over a year ago

looks like YOU forgot this feature ;)

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