Query using multiple conditions

I recently discovered (sadly) that WebSQL is no longer being supported for HTML5 and that IndexedDB will be replacing it instead.

I'm wondering if there is any way to query or search through the entries of an IndexedDB in a similar way to how I can use SQL to search for an entry satisfying multiple conditions.

I've 开发者_如何学JAVAseen that I can search through IndexedDB using one condition with the KeyRange. However, I can't seem to find any way to search two or more columns of data without grabbing all the data from the database and doing it with for loops.

I know this is a new feature that's barely implemented in the browsers, but I have a project that I'm starting and I'm researching the different ways I could do it.

Thank you!

Check out this answer to the same question. It is more detailed than the answer I give here. The keypath parameter to store.createIndex and IDBKeyRange methods can be an array. So, crude example:

// In onupgradeneeded
var store = db.createObjectStore('mystore');
store.createIndex('myindex', ['prop1','prop2'], {unique:false});

// In your query section
var transaction = db.transaction('mystore','readonly');
var store = transaction.objectStore('mystore');
var index = store.index('myindex');
// Select only those records where prop1=value1 and prop2=value2
var request = index.openCursor(IDBKeyRange.only([value1, value2]));
// Select the first matching record
var request = index.get(IDBKeyRange.only([value1, value2]));

Let's say your SQL Query is something like:

SELECT * FROM TableName WHERE Column1 = 'value1' AND Column2 = 'value2'

Equivalent Query in JsStore library:

var Connection = new JsStore.Instance("YourDbName");
Connection.select({
    From: "YourTableName"
    Where: {
        Column1: 'value1',
        Column2: 'value2'
    },
    OnSuccess:function (results){
        console.log(results);
    },
    OnError:function (error) {
        console.log(error);
    }
});

Now, if you are wondering what JsStore is, let me tell you it is a library to query IndexedDB in a simplified manner. Click here to learn more about JsStore

I mention some suggestions for querying relationships in my answer to this question, which may be of interest:

Conceptual problems with IndexedDB (relationships etc.)

As to querying multiple fields at once, it doesn't look like there's a native way to do that in IndexedDB (I could be wrong; I'm still new to it), but you could certainly create a helper function that used a separate cursor for each field, and iterated over them to see which records met all the criteria.

Yes, opening continuous key range on an index is pretty much that is in indexedDB. Testing for multiple condition is not possible in IndexedDB. It must be done on cursor loop.

If you find the solution, please let me know.

BTW, i think looping cursor could be very fast and require less memory than possible with Sqlite.

I'm a couple of years late, but I'd just like to point out that Josh's answer works on the presumption that all of the "columns" in the condition are part of the index's keyPath.

If any of said "columns" exist outside the the index's keyPath, you will have to test the conditions involving them on each entry which the cursor created in the example iterates over. So if you're dealing with such queries, or your index isn't unique, be prepared to write some iteration code!

In any case, I suggest you check out BakedGoods if you can represent your query as a boolean expression.

For these types of operations, it will always open a cursor on the focal objectStore unless you're performing a strict equality query (x ===? y, given x is an objectStore or index key), but it will save you the trouble writing your own cursor iteration code:

bakedGoods.getAll({
    filter: "keyObj > 5 && valueObj.someProperty !== 'someValue'",
    storageTypes: ["indexedDB"],
    complete: function(byStorageTypeResultDataObj, byStorageTypeErrorObj){}
});

Just for the sake of complete transparency, BakedGoods is maintained by moi.