mongodb 通过 Haskell：创建文本搜索索引

Question

为了通过文本在 mongo 数据库中搜索项目，我需要根据 documentation 创建一个索引。

下面的代码创建了这个索引：

index is Index {iColl = "note", iKey = [ text: 1], iName = "text_1", iUnique = False, iDropDups = False}

为什么代码会出现这个错误？

*** Exception: expected "results" in [ ok: 0.0, errmsg: "no text index for: db.note"]

更新 以下更新的代码出现相同的错误。我改变的是我现在使用createIndex。

         let order = [(fieldToText TextField) =: (1 :: Int32)]
              docIndex =  index (docTypeToText docType) order
          actionResult <- run pipe dbName $ createIndex docIndex
          case actionResult of
            Left failure -> do putStrLn $ show failure
                               return []
            Right () -> do
              putStrLn $ "index is " ++ show docIndex
              run pipe dbName $ ensureIndex docIndex
              mDoc <- run pipe dbName $ runCommand
                [pack "text" =: (docTypeToText docType),
                  pack "search" =: (pack $ unwords keywords),
                    pack "filter" =: (selector $ selection query)]
              case mDoc of
                Left failure -> do putStrLn $ show failure
                                   return []
                Right doc -> let Array results = valueAt (pack "results") doc
                                 ds = [d | Doc d <- results]
                             in return ds

更新见下方评论。

Answer 1

我的猜测是：在开发 Haskell 驱动程序时，MongoDB 根本不支持全文索引。因此，当前版本的驱动无法创建"text" 索引。

更新 1：再想一想，您或许可以创建一个 "text" 索引，将文档插入到 "system.indexes"，就像驱动程序中的 done 一样。

更新 2：使用 createIndex 无济于事，因为 MongoDB doesn't allow 将 "text" 传递为 iKey。这是一种似乎有效的方法：

createTextIndex :: Collection -> String -> [Label] -> Action IO ()
createTextIndex col name keys = do
    db <- thisDatabase
    let doc = [ "ns"   =: db <.> col
              , "key"  =: [key =: ("text" :: String) | key <- keys]
              , "name" =: name
              ]
    insert_ "system.indexes" doc

search :: Collection -> String -> Document -> Action IO Document
search col term filter = runCommand [ "text"   =: col
                                    , "search" =: term
                                    , "filter" =: filter
                                    ]

main :: IO ()
main = do
    pipe <- runIOE $ connect host
    res  <- access pipe master "test" $ do
        createTextIndex "foo" "foo-index" ["bar"]
        search "foo" "some-keyword" []
    print res
  where
    host = Host "localhost" $ UnixSocket "/tmp/mongodb-27017.sock"