Fix Postgres TODOs (#379)

* Use $(fields) in Guide.Database.Queries.Select

* Checking schema hash is hard and not really necessary

* Explain why we store deleted objects

back/src/Guide/Database/Queries/Select.hs

@@ -114,9 +114,9 @@ selectCategoryRowByItemMaybe itemId = do
 
 -- | Get a list of available categories' IDs.
 --
--- Includes categories marked as deleted.
---
--- TODO explain why we store deleted categories at all.
+-- Includes categories marked as deleted. See
+-- <https://www.notion.so/aelve/Handling-of-deleted-objects-aa21056f7bdb43d2b635a8f6f93541a3>
+-- for an explanation of why we store deleted objects at all.
 selectCategoryIds :: ExceptT DatabaseError Transaction [Uid Category]
 selectCategoryIds = do
   let statement :: Statement () [Uid Category]
@@ -206,7 +206,7 @@ selectDeletedItemRowsByCategory catId = do
         |]
   lift $ HT.statement catId statement
 
--- Get available ItemRows belonging to a category.
+-- | Get available ItemRows belonging to a category.
 --
 -- Returns item rows sorted by order.
 selectItemRowsByCategory :: Uid Category -> ExceptT DatabaseError Transaction [ItemRow]

back/src/Guide/Database/Schema.hs

@@ -36,8 +36,6 @@ migrations =
 -- not create a database if it does not exist yet. You should create the
 -- database manually by doing @CREATE DATABASE guide;@ or run Postgres with
 -- @POSTGRES_DB=guide@ when running when running the app for the first time.
---
--- TODO: check schema hash as well, not just schema version?
 setupDatabase :: IO ()
 setupDatabase = do
   conn <- connect

back/src/Guide/Database/Types.hs

@@ -116,12 +116,9 @@ instance FromPostgresRow TraitRow
 
 -- | Convert CategoryRow to Category.
 --
--- | To fetch items (they have an order) use 'getItemRowsByCategory' from 'Get' module.
--- | To fetch deleted items use 'getDeletedItemRowsByCategory' from 'Get' module
---
--- TODO: somehow handle the case when item IDs don't match the @itemsOrder@?
---
--- TODO: use 'fields' for pattern-matching.
+-- To fetch items, use @selectItemRowsByCategory@ from
+-- "Guide.Database.Queries.Select". To fetch deleted items, use
+-- @selectDeletedItemRowsByCategory@.
 categoryRowToCategory
   :: "items" :! [Item]
   -> "itemsDeleted" :! [Item]
@@ -130,7 +127,7 @@ categoryRowToCategory
 categoryRowToCategory
   (arg #items -> items)
   (arg #itemsDeleted -> itemsDeleted)
-  CategoryRow{..}
+  $(fields 'CategoryRow)
   =
   Category
     { categoryUid = categoryRowUid
@@ -143,10 +140,18 @@ categoryRowToCategory
     , categoryItemsDeleted = itemsDeleted
     , categoryEnabledSections = categoryRowEnabledSections
     }
+  where
+    -- Ignored fields
+    _ = categoryRowDeleted
+    _ = categoryRowItemsOrder
 
 -- | Convert Category to CategoryRow.
-categoryToRowCategory :: Category -> "deleted" :! Bool -> CategoryRow
-categoryToRowCategory $(fields 'Category) (arg #deleted -> deleted) = CategoryRow
+categoryToRowCategory
+  :: Category
+  -> "deleted" :! Bool
+  -> CategoryRow
+categoryToRowCategory $(fields 'Category) (arg #deleted -> deleted) =
+  CategoryRow
     { categoryRowUid = categoryUid
     , categoryRowTitle = categoryTitle
     , categoryRowCreated = categoryCreated
@@ -163,8 +168,9 @@ categoryToRowCategory $(fields 'Category) (arg #deleted -> deleted) = CategoryRo
 
 -- | Convert ItemRow to Item.
 --
--- | To fetch traits (they have an order) use 'getTraitRowsByItem' from 'Get' module.
--- | To fetch deleted traits use 'getDeletedTraitRowsByItem' from 'Get' module
+-- To fetch traits, use @getTraitRowsByItem@ from
+-- "Guide.Database.Queries.Select". To fetch deleted traits, use
+-- @getDeletedTraitRowsByItem@.
 itemRowToItem
   :: "proTraits" :! [Trait]
   -> "proDeletedTraits" :! [Trait]
@@ -177,7 +183,7 @@ itemRowToItem
   (arg #proDeletedTraits -> proDeletedTraits)
   (arg #conTraits -> conTraits)
   (arg #conDeletedTraits -> conDeletedTraits)
-  ItemRow{..}
+  $(fields 'ItemRow)
   =
   Item
     { itemUid = itemRowUid
@@ -195,10 +201,15 @@ itemRowToItem
     }
   where
     prefix = "item-notes-" <> uidToText itemRowUid <> "-"
+    -- Ignored fields
+    _ = (itemRowConsOrder, itemRowProsOrder)
+    _ = itemRowCategoryUid
+    _ = itemRowDeleted
 
 -- | Convert Item to ItemRow.
 itemToRowItem :: Uid Category -> "deleted" :! Bool -> Item -> ItemRow
-itemToRowItem catId (arg #deleted -> deleted) $(fields 'Item) = ItemRow
+itemToRowItem catId (arg #deleted -> deleted) $(fields 'Item) =
+  ItemRow
     { itemRowUid = itemUid
     , itemRowName = itemName
     , itemRowCreated = itemCreated
@@ -218,12 +229,18 @@ itemToRowItem catId (arg #deleted -> deleted) $(fields 'Item) = ItemRow
 
 -- | Convert TraitRow to Trait.
 traitRowToTrait :: TraitRow -> Trait
-traitRowToTrait TraitRow{..} = Trait
+traitRowToTrait $(fields 'TraitRow) =
+  Trait
     { traitUid = traitRowUid
     , traitContent = toMarkdownInline traitRowContent
     }
+  where
+    -- Ignored fields
+    _ = traitRowItemUid
+    _ = traitRowType
+    _ = traitRowDeleted
 
--- Convert Trait to TraitRow
+-- | Convert Trait to TraitRow.
 traitToTraitRow
   :: Uid Item
   -> "deleted" :! Bool