ydn-db: how to make any query more complex than getting a single record by id?

Question

Using the packaged ydn-db library from here: http://git.yathit.com/ydn-db/downloads/ydn.db-jquery-0.7.12.js . Same happens with https://storage.cloud.google.com/download.yathit.com/ydn-db/build/zsk-ydn.db-dev-0.7.15.js .

var db = new ydn.db.Storage("mydb");
var clog = function(r) { console.log(r); }

db.put({name: "store1", keyPath: "id"}, {id: "id1", value: "value1"});
db.put({name: "store1", keyPath: "id"}, {id: "id2", value: "value2"});

db.get("store1", "id1").done(clog); // works fine

// Example as mentioned in the docs here: http://dev.yathit.com/ydn-db/getting-started.html
var reverse = false, limit = 10;
db.values(new ydn.db.Cursors("store1", "id", null, reverse), limit).done(clog)
// TypeError: Cannot call method 'getName' of null

// Also adapted from docs:
db.values(ydn.db.IndexValueCursors.where("store1", "id", "=", "id1")).done(clog)
// TypeError: Cannot call method 'getName' of null

// Also adapted from docs:
var iter = new ydn.db.ValueCursors("store1", ydn.db.KeyRange.starts("a"))
db.open(iter, clog, "readwrite")
// ydn.error.ArgumentException: Second argument must be cursor range iterator.

The functionality of the packaged library just doesn't seem to align with the docs. Any tips?

Kyaw Tun · Answer 1 · 2013-09-09T06:00:16.407

1

Actually, your schema don't have index name id, so the correct code should be as follow.

var db = new ydn.db.Storage("mydb");
var clog = function(r) { console.log(r); }

db.put({name: "store1", keyPath: "id"}, {id: "id1", value: "value1"});
db.put({name: "store1", keyPath: "id"}, {id: "id2", value: "value2"});

db.get("store1", "id1").done(clog); // works fine


 // Example as mentioned in the docs here: http://dev.yathit.com/ydn-db/getting-started.html
var reverse = false, limit = 10;
db.values(new ydn.db.KeyCursors("store1", null, reverse), limit).done(clog)
// TypeError: Cannot call method 'getName' of null

// Also adapted from docs:
db.values(ydn.db.ValueCursors.where("store1",  "=", "id1")).done(clog)
// TypeError: Cannot call method 'getName' of null

// Also adapted from docs:
var iter = new ydn.db.ValueCursors("store1", ydn.db.KeyRange.starts("i"))
var pnt = function(r) {console.log(r.getValue())}
db.open(pnt, iter, "readwrite")

Error message is definitely not informative. I push a patch, so next time, it gives index not found error.

There is api changes in open method, as well. Documentation need to be update.

Edit: more complex query can be found in http://dev.yathit.com/ydn-db/nosql-query.html

edited Sep 09 '13 at 06:00

answered Sep 09 '13 at 05:01

Kyaw Tun

12,447
10
56
83

These snippets do produce output with no errors, but I'm unclear on what these queries actually do now that no column is actually specified. How would I say, sort by the `value` column, or do a query analogous to `select * from store1 where value = 'value1'`? If I need to do something with a schema that's fine. – Andrew Magee Sep 09 '13 at 05:27
I agree that it is not clear without consulting documentation. I am also thinking LINQ like query interface on top of these range iterators. Currently ydn-db expose as IndexedDB API provided. – Kyaw Tun Sep 09 '13 at 05:51
Ok but is it possible to do these things with the current API at all? – Andrew Magee Sep 09 '13 at 06:44
The last second query is `select * from store1 where value = 'value1'`. YDN-DB provide all query possible with IndexedDB. You have to be specific about query. I don't know how *complex query*, you means. – Kyaw Tun Sep 09 '13 at 07:21
Sorry I don't see how any of the queries can be `select * from store1 where value = 'value1'` since none of them reference `value`... – Andrew Magee Sep 09 '13 at 12:04
Sorry, yes `id` have to be changed to `value` and `value` must be defined as index in database schema. – Kyaw Tun Sep 10 '13 at 04:58
Can you give an example? I couldn't get any queries referencing any columns to work, hence my original question. The queries in your answer don't reference any columns at all so I can't use them either. – Andrew Magee Sep 10 '13 at 11:40

score 1 · Accepted Answer · answered Sep 11 '13 at 01:45

Ok, finally got it from the link in the previous answer:

// Equivalent to: SELECT * FROM store1 where value = 'value1':
var keyRange = ydn.db.KeyRange.only("value1");
var cursor = new ydn.db.IndexValueCursors("store1", "value", keyRange);
db.get(cursor, keyRange).then(function(record) {
   console.log("record:", record);
}, function(err) {
   throw err;
});

ydn-db: how to make any query more complex than getting a single record by id?

2 Answers2