Question

It seems I don’t understand how text index in IxSet should work. Here, I created a unit-test that indexes items by tags field, and then query items by tag “tag”. It should (from my perspective) give me back all 3 items (because they all have tag “tag”), but seems they don’t. And I don’t understand why.

{-# LANGUAGE DeriveDataTypeable #-}

import Test.HUnit
import Data.IxSet
import Data.List.Split ( splitOn )
import Data.Data ( Data, Typeable )

data TaggedItem = TaggedItem { getTags :: String }
                  deriving ( Show, Ord, Eq, Data, Typeable )

data Tag = Tag String
           deriving ( Show, Ord, Eq, Data, Typeable )

getTagStrings :: TaggedItem -> [Tag]
getTagStrings = map Tag . splitOn "," . getTags

instance Indexable TaggedItem where
  empty = ixSet
            [ ixFun getTagStrings ]

test3 = TestCase (
  assertEqual "ixFun multiple tags test"
  3
  (size (index @= (Tag "tag"))) )
  where items = [ TaggedItem "tag,tag1,tag2"
                , TaggedItem "tag,tag1,tag2"
                , TaggedItem "tag,tag1,tag2" ]
        index = fromList items

tests = TestList [
  -- TestLabel "test1" test1,
  -- TestLabel "test2" test2,
  TestLabel "test3" test3]

main = do
  runTestTT tests

Update:

Hmm, quite interesting. I’ve added field “name” and made at each item name to be different, and now it works.

{-# LANGUAGE DeriveDataTypeable #-}

import Test.HUnit
import Data.IxSet
import Data.List.Split ( splitOn )
import Data.Data ( Data, Typeable )

newtype TaggedItemName = TaggedItemName { unTaggedItemName :: String }
                       deriving ( Show, Ord, Eq, Data, Typeable )

data TaggedItem = TaggedItem { getName :: TaggedItemName, getTags :: String }
                deriving ( Show, Ord, Eq, Data, Typeable )

data Tag = Tag String
           deriving ( Show, Ord, Eq, Data, Typeable )

getTagStrings :: TaggedItem -> [Tag]
getTagStrings = map Tag . splitOn "," . getTags

instance Indexable TaggedItem where
  empty = ixSet
            [ ixFun getTagStrings ]

test3 = TestCase (
  assertEqual "ixFun multiple tags test"
  3
  (size (index @= (Tag "tag"))) )
  where items = [ TaggedItem (TaggedItemName "name1") "tag,tag1,tag2"
                , TaggedItem (TaggedItemName "name2") "tag,tag1,tag2"
                , TaggedItem (TaggedItemName "name3") "tag,tag1,tag2" ]
        index = fromList items

tests = TestList [
  -- TestLabel "test1" test1,
  -- TestLabel "test2" test2,
  TestLabel "test3" test3]

main = do
  runTestTT tests

Works. So maybe IxSet considered those items as same and merged them somehow (?)

Answer 1

Yes, it seems IxSet merges equal values. I took first example and changed it so that it did:

  where items = [ TaggedItem "tag,tag1,tag2"
                , TaggedItem "tag,tag3,tag4"
                , TaggedItem "tag,tag5,tag6" ]

And now it also works.