Slow Queries in CouchBase Lite - Android

[Chris M]

Hi All,

CBL-Android.

We're finding our queries are running pretty slow (4-5 seconds) with  50 records/doc

Speed does not improve on 2nd/3rd/4th runs...always the same.

I think the view is never indexing - so its running full search every run.

I'm guessing there is some setting/config that i'm missing. (index=auto?)

Anyone have a solution?

Thanks CM

[Jens Alfke]

On Jul 17, 2013, at 12:40 PM, Chris M <appbr...@gmail.com> wrote:

I think the view is never indexing - so its running full search every run.

I'm guessing there is some setting/config that i'm missing. (index=auto?)

No, indexing should be automatic.

Do you have a complex reduce function? CBL doesn’t precompute reduced values the way CouchDB does, so it has to run the reduce function over all the rows on every query. But this should only get slow if you have large amounts of data.

I’m not familiar with Android dev tools, but if you could profile the app while querying to see where the time is being spent, that would help narrow it down.

—Jens

[Олег Рак]

Hi Jens, i'm working with Chris M.

First of all we are not using any reduce functions.

Here is a piece of app code.

        CBLView getGadgetsByParentIdView = db.getViewNamed(gadgetsByParentIdViewName);

        if (getGadgetsByParentIdView.getMapBlock() == null) {

            getGadgetsByParentIdView.setMapReduceBlocks(

                new CBLViewMapBlock() {

                    @Override

                    public void map(Map<String, Object> stringObjectMap, CBLViewMapEmitBlock cblViewMapEmitBlock) {

                        if (Gadget.class.getSimpleName().equals(stringObjectMap.get(META_BASE_TYPE_PROP))) {

                            cblViewMapEmitBlock.emit(stringObjectMap.get(PARENT_GADGET_ID_PROP), stringObjectMap.get(ID_PROP));

                        }

                    }

                },

                null,

                VIEWS_VERSION

            );

        }

The problem is next:
Each time after app is started, first view-function call is slow(looks like db is updating index), next calls are fast.

It's strange because there are no changes in db between two app starts, so there is no reason to update index

CBLView getGadgetsByParentIdView = db.getViewNamed(gadgetsByParentIdViewName);
is returning CBLView with empty MapBlock when i'm getting it rigth after app start, so MapReduceBlock must be setted again.

I'm not sure what is the reason, but it looks like DB isn't storing MapBlock with view-function and when i'm seting it to CBLView again then indexing occurs.

Thanks in advance.

[Jens Alfke]

On Jul 18, 2013, at 4:43 AM, Олег Рак <use...@gmail.com> wrote:

I'm not sure what is the reason, but it looks like DB isn't storing MapBlock with view-function and when i'm seting it to CBLView again then indexing occurs.

The MapBlock itself can’t be stored (it’s live code, not a string), so that’s what the version parameter is for — it gets stored instead. If you register the view with a different version string than the one stored in the db, the index is cleared. But you should be OK as long as “VIEWS_VERSION” is a constant that you’re not changing.

—Jens

[Traun Leyden]

If VIEWS_VERSION is indeed a constant, go ahead and file an issue with instructions how to reproduce including code snippets which show how you are initializing CBLite.

[Олег Рак]

If VIEWS_VERSION is indeed a constant, go ahead and file an issue with instructions how to reproduce including code snippets which show how you are initializing CBLite.

VIEWS_VERSION is a constant value. Ok guys, i'll open issue on github. Thanks!

[Олег Рак]

Here is a link to issue on github:
https://github.com/couchbase/couchbase-lite-android/issues/37