Speeding up Cloudant query for type text index - couchdb

Question

We have a table with this type of structure:
{_id:15_0, createdAt: 1/1/1, task_id:[16_0, 17_0, 18_0], table:”details”, a:b, c: d, more}
We created indexes using
{
"index": {},
"name": "paginationQueryIndex",
"type": "text"
}
It auto created
{
"ddoc": "_design/28e8db44a5a0862xxx",
"name": "paginationQueryIndex",
"type": "text",
"def": {
"default_analyzer": "keyword",
"default_field": {
},
"selector": {
},
"fields": [
],
"index_array_lengths": true
}
}
We are using the following query
{
"selector": {
"createdAt": { "$gt": 0 },
"task_id": { "$in": [ "18_0" ] },
"table": "details"
},
"sort": [ { "createdAt": "desc" } ],
"limit”: 20
}
It takes 700-800 ms for first time, after that it decreases to 500-600 ms
Why does it take longer the first time?
Any way to speed up the query?
Any way to add indexes to specific fields if type is “text”? (instead of indexing all the fields in these records)

Answer 1

You could try creating the index more explicitly, defining the type of each field you wish to index e.g.:
{
"index": {
"fields": [
{
"name": "createdAt",
"type": "string"
},
{
"name": "task_id",
"type": "string"
},
{
"name": "table",
"type": "string"
}
]
},
"name": "myindex",
"type": "text"
}
Then your query becomes:
{
"selector": {
"createdAt": { "$gt": "1970/01/01" },
"task_id": { "$in": [ "18_0" ] },
"table": "details"
},
"sort": [ { "createdAt": "desc" } ],
"limit": 20
}
Notice that I used strings where the data type is a string.
If you're interested in performance, try removing clauses from your query one at-a-time to see if one is causing the performance problem. You can also look at the explanation of your query to see if it using your index correctly.
Documentation on creating an explicit text query index is here