Cloudant search with grouping on array-type field - cloudant

Question

I have a database with documents like these:
{_id: "1", module:["m1"]}
{_id: "2", module:["m1", "m2"]}
{_id: "3", module:["m3"]}
There is an search index created for these documents with the following index function:
function (doc) {
doc.module && doc.module.forEach &&
doc.module.forEach(function(module){
index("module", module, {"store":true, "facet": true});
});
}
The index uses "keyword" analyzer on module field.
The sample data is quite small (11 documents, 3 different module values)
I have two issues with queries that are using group_field=module parameter:
Not all groups are returned. I get 2 out of 3 groups that I expect. Seems like if a document with ["m1", "m2"] is returned in the "m1" group, but there is no "m2" group. When I use counts=["modules"] I get complete lists of distinct values.
I'd like to be able to get something like:
{
"total_rows": 3,
"groups": [
{ "by": "m1",
"total_rows": 1,
"rows": [ {_id: "1", module: "m1"},
{_id: "2", module: "m2"}
]
},
{ "by": "m2",
"total_rows": 1,
"rows": [ {_id: "2", module: "m2"} ]
},
....
]
}
When using group_field, bookmark is not returned, so there is no way to get the next chunk of the data beyond 200 groups or 200 rows in a group.

Answer 1

Cloudant Search is based on Apache Lucene, and hence has its properties/limitations.
One limitation of grouping is that "the group field must be a single-valued indexed field" (Lucene Grouping), hence a document can be only in one group.
Another limitation/property of grouping is that topNGroups and maxDocsPerGroup need to be provided in advance, and in Cloudant case the max numbers are 200 and 200 (they can be set lower by using group_limit and limit parameters).