How to access an FTS table in SQLite.swift using the IN condition

Question

I'm trying to query an FTS table using SQLite.swift. Previously I have done it in Android. The essence of what I am trying to do is this:

SELECT *
FROM t2
WHERE id IN (SELECT docid
             FROM fts_table
             WHERE col_text MATCH 'something')

From the SQLite.swift documentation I see the IN condition can be written like this:

users.filter([1, 2, 3, 4, 5].contains(id))
// SELECT * FROM "users" WHERE ("id" IN (1, 2, 3, 4, 5))

And virtual tables can be queried like this:

let wonderfulEmails = emails.match("wonder*")
// SELECT * FROM "emails" WHERE "emails" MATCH 'wonder*'

let replies = emails.filter(subject.match("Re:*"))
// SELECT * FROM "emails" WHERE "subject" MATCH 'Re:*'

However, I can't figure out how to combine these. I don't really want to have to execute arbitrary SQL (although this is now working thanks to help from this answer).

Update

Here is my most recent try that is not working:

let tableText = Table("t2")
let id = Expression<Int64>("id")
let someColumn = Expression<String>("someColumn")

let tableFts = VirtualTable("fts_table")
let columnDocId = Expression<Int64>("docId")


let ftsQuery = tableFts
    .select(columnDocId)
    .filter(tableFts.match("something"))
let tableQuery = tableText
    .filter((try db.prepare(ftsQuery))
        .contains(id))                       // <-- error

for row in try db.prepare(tableQuery) {
    print(row[someColumn])
}

where the line with contains(id) throws the error:

Cannot convert value of type 'Expression' to expected argument type '@noescape (Row) throws -> Bool'

Answer 1

I ended up just running the raw SQL command. This doesn't exactly answer what I was asking in the question (since it doesn't use the pure SQLite.swift API) but for those who just need to get something working, ... it works.

Here is a modified example that I pulled from some of my source code.

static func findLinesContaining(_ searchTerms: String, forSearchScope scope: SearchScope) throws -> [TextLines] {

    guard let db = SQLiteDataStore.sharedInstance.TextDB else {
        throw DataAccessError.datastore_Connection_Error
    }

    // TODO: convert to SQLite.swift syntax rather than using a SQL string
    var statement: Statement? = nil
    switch scope {
    case .wholeCollection:
        statement = try db.run("SELECT bookId, chapterId, lineId, lineText" +
            " FROM lines" +
            " WHERE rowid IN (SELECT docid FROM fts_table" +
            " WHERE fts_table MATCH ?);", searchTerms)

    case .singleBook(let chosenBookId):
        statement = try db.run("SELECT bookId, chapterId, lineId, lineText" +
            " FROM lines" +
            " WHERE rowid IN (SELECT docid FROM fts_table" +
            " WHERE fts_table MATCH ?) AND bookId = ?;", [searchTerms, chosenBookId])
    }


    var returnList: [TextLine] = []
    for row in statement! {

        let line = TextLine()
        if let bookId = row[0] as? Int64,
            let chapterId = row[1] as? Int64,
            let lineId = row[2] as? Int64,
            let text = row[3] as? String {

            line.bookId = Int(bookId)
            line.chapterId = Int(chapterId)
            line.lineId = Int(lineId)
            line.lineText = text
        }

        returnList.append(line)
    }

    return returnList
}

The above code is untested after renaming variables and classes for use on SO. You have my permission to edit the code if you find a bug.