Comment 0 for bug 1214538

It seems that query's only return results of documents, where all the document's fields are indexed [regardless of whether or not those fields are being queried].

I've included a number of examples below, I hope they clarify the situation:

Examples:

Database definition:

    U1db.Database {
        id: theDB
        path: "indextest.db"
    }

Two sample documents: the first has only a "title" field, the second has both "title" and "num" fields:

    U1db.Document {
        database: theDB
        create: true
        docId: "vic"
        defaults: {"title": "vic"}
    }

    U1db.Document {
        database: theDB
        create: true
        docId: "xqwzts"
        defaults: {
            "title": "xqwzts",
            "num": "123"
        }
    }

Index only the title field since it is what I care about querying:

    U1db.Index {
        database: theDB
        id: theIndex
        expression: ["title"]
    }

An empty query which should match all documents in the index:

    U1db.Query {
        id: theQuery
        index: theIndex
    }

Expected result: both documents should be returned

Action result: only the first document is returned

Detailed output:

JSON.stringify(theDB.listDocs())

    {"0":"vic","1":"xqwzts"}

JSON.stringify(theIndex)

    {"database":{"error":"","objectName":"","path":"indextest.db"},"name":"","objectName":"","expression":{"0":"title"}}

JSON.stringify(theQuery)

    {"index":{"database":{"error":"","objectName":"","path":"indextest.db"},"name":"","objectName":"","expression":{"0":"title"}},"objectName":"","results":[{"title":"vic"}],"documents":{"0":"vic"}}

Specifying the query to search for title = "*" makes no difference:

    U1db.Query {
        id: theQuery
        index: theIndex
        query: [{"title": "*"}]
    }

JSON.stringify(theQuery)

    {"index":{"database":{"error":"","objectName":"","path":"indextest.db"},"name":"","objectName":"","expression":{"0":"title"}},"objectName":"","results":[{"title":"vic"}],"documents":{"0":"vic"},"query":[{"title":"*"}]}

It seems the second document simply isn't in the index, so no query will return it.

To add the second document to the index we must add all fields of the document to the index expression:

    U1db.Index {
        database: theDB
        id: theIndex
        expression: ["title", "num"]
    }

And remove the query clause to have the query return all documents in the index:

   U1db.Query {
        id: theQuery
        index: theIndex
    }

So now the output becomes:

JSON.stringify(theIndex)

    {"database":{"error":"","objectName":"","path":"indextest.db"},"name":"","objectName":"","expression":{"0":"title","1":"num"}}

JSON.stringify(theQuery)

    {"index":{"database":{"error":"","objectName":"","path":"indextest.db"},"name":"","objectName":"","expression":{"0":"title","1":"num"}},"objectName":"","results":[{"title":"vic"},{"num":"123"}],"documents":{"0":"vic","1":"xqwzts"}}

But now in order to add a query clause all the fields in the index which are also in the document have to be included.

    U1db.Query {
        id: theQuery
        index: theIndex
        query: [{"title": "*"}]
    }

JSON.stringify(theQuery)

    {"index":{"database":{"error":"","objectName":"","path":"indextest.db"},"name":"","objectName":"","expression":{"0":"title","1":"num"}},"objectName":"","results":[{"title":"vic"}],"documents":{"0":"vic"},"query":[{"title":"*"}]}

In order to actually return all the documents with title=* we have to also specify that num=*

    U1db.Query {
        id: theQuery
        index: theIndex
        query: [{"title": "*"}, {"num": "*"}]
    }

JSON.stringify(theQuery)

    {"index":{"database":{"error":"","objectName":"","path":"indextest.db"},"name":"","objectName":"","expression":{"0":"title","1":"num"}},"objectName":"","results":[{"title":"vic"},{"num":"123"}],"documents":{"0":"vic","1":"xqwzts"},"query":[{"title":"*"},{"num":"*"}]}

Conclusion:

- In order to be included in the index, ALL fields in a document must be included in the index's expression clause.
- In order to be returned by a query, ALL fields in a document [which are also in the index] must be included in the query's query clause.

This is pretty problematic with large/complicated documents where including every single field in the expression/query clause is not really feasible.