Count.hs

{-# LANGUAGE CPP #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE OverloadedStrings #-}

{- | Thanks to our dynamic 'Opaleye' effect, we can write an alternative interpreter which,
as well as performing SQL operations as before, will also keep a tally of the number of
SQL operations (SELECTs, INSERTs etc) that have been performed. This is really useful for debugging.

The intended use-case is a sort of benchmark that runs several Opaleye operations for different
"sizes", counts the SQL operations, and prints the tallies to the console. This lets us detect if
some datbase operations are ineffecient.

For example, suppose our model has users with @UserId@s; those users an have multiple @Transaction@s, which
are composed of multiple @SubTransaction@s etc.
To insert a group of new users, we would need to insert the users, insert the transactions, and insert the subtransactions.
Ideally, the number of @INSERT@s should not depend on the number of @User@s or the number or size of their @Transactions@.
We would expect the number of SELECTs to remain basically constant (O(1)), while the execution time might grow linearly (O(u * t * s)).

A very naive implementation might be:

@
insertUsersNaive :: ('Opaleye' :> es) => [User] -> Eff es ()
insertUsersNaive users = for_ users $ \user -> do
  insertUserFlat user
  for (transactions user) $ \transaction -> do
    insertTransactionFlat transaction
    for (subTransactions transaction) $ \subTransaction -> do
      insertSubTransactionFlat subTransaction
@

However, if we ran a "benchmark" that looked something like this:

@
u1, u5, u10, u50 :: [User]
u1 = [User {transactions = [Transaction [SubTransaction]]}] -- one user, one transaction, one sub-transaction
u5 = ...  -- five users, each with five transactions, each with 5 sub-transactions

benchmark :: ('Opaleye' :> es, State SQLOperationCounts :> es, IOE :> es) => Eff es ()
benchmark = for_ [(1, u1), (5, u5), (10, u10), (50, u50)] $ \(n, users) -> do
  (counts, ()) <- withCounts $ insertUsersNaive users
  liftIO . putStrLn $ "Counts at n=" <> show n <> ": " <> 'renderCountsBrief' counts

main :: IO ()
main = runEff . 'Conn.runWithConnectInfo' connInfo . evalState @SQLOperationCounts mempty . runOpaleyeWithConnectionCounting $ benchmark
  where
    connInfo = ...
@

We will probably see something like:

@
Counts at n=1: INSERT: 3
Counts at n=5: INSERT: 155
Counts at n=10: INSERT: 1110
Counts at n=50: INSERT: 127550
@

This is obviously going to have a severe performance impact. Rearranging our implementation of @insertUsers@:

@
insertUsersBetter :: ('Opaleye' :> es) => [User] -> Eff es ()
insertUsersBetter users = do
  let transactions_ = concatMap transactions users
      subTransactions_ = concatMap subTransactions transactions_
  insertUsersFlat users
  insertTransactionsFlat transactions_
  insertSubTransactionsFlat subTransactions_
@

As long as @insertTransactionsFlat@ etc are smart enough to only do one 'runInsert', then we should now get:

@
Counts at n=1: INSERT: 3
Counts at n=5: INSERT: 3
Counts at n=10: INSERT: 3
Counts at n=50: INSERT: 3
@

Note that we used 'renderCountsBrief' for simplicity. If we wanted to debug in more detail, we could have used
'renderCounts' instead:

@
Counts at n=1: INSERT: user: 1
                       transaction: 1
                       sub_transaction: 1
Counts at n=5: INSERT: user: 5
                       transaction: 25
                       sub_transaction: 125
Counts at n=10: INSERT: user: 10
                        transaction: 100
                        sub_transaction: 1000
Counts at n=50: INSERT: user: 50
                        transaction: 2500
                        sub_transaction: 125000
@
-}
module Bluefin.Opaleye.Count
  ( -- * Counting SQL operations
    SQLOperationCounts (..)
  , opaleyeAddCounting
  , withCounts

    -- * Pretty-printing
  , printCounts
  , printCountsBrief
  , renderCounts
  , renderCountsBrief
  , prettyCounts
  , prettyCountsBrief
  )
where

import Bluefin.Compound
import Bluefin.Eff
import Bluefin.Opaleye.Effect
import Bluefin.State
import Control.Monad.IO.Class
import qualified Data.List.NonEmpty as NE
import Data.Map (Map)
import qualified Data.Map as Map
import Data.Maybe (catMaybes, mapMaybe)
import qualified Data.Text as T
import Database.PostgreSQL.Simple.Types (QualifiedIdentifier (..))
import GHC.Generics
import Numeric.Natural
import qualified Opaleye as O
import qualified Opaleye.Internal.PrimQuery as O (TableIdentifier (..))
import qualified Opaleye.Internal.Table as O
import qualified Text.PrettyPrint as P
import qualified Text.PrettyPrint.HughesPJClass as P

------------------------------------------------------------
-- Tallying SQL operations

{- | This tracks the number of SQL operations that have been performed in the
'Opaleye' effect, along with which table it was performed on (where possible).

@INSERT@, @DELETE@ and @UPDATE@ operations act on one table only, so we can tally the number
of each that are performed on each table (indexed by a t'QualifiedIdentifier').
@SELECT@ operations can act on multiple tables, so we just track the total number of selects.

If required, t'SQLOperationCounts' can be constructed using 'Monoid' and combined using 'Semigroup'.

We use non-negative 'Natural's as a tally since a negative number of operations makes no sense.
-}
data SQLOperationCounts = SQLOperationCounts
  { sqlSelects :: Natural
  , sqlInserts :: Map QualifiedIdentifier Natural
  , sqlDeletes :: Map QualifiedIdentifier Natural
  , sqlUpdates :: Map QualifiedIdentifier Natural
  }
  deriving (Show, Eq, Generic)

instance Semigroup SQLOperationCounts where
  SQLOperationCounts s1 i1 d1 u1 <> SQLOperationCounts s2 i2 d2 u2 =
    SQLOperationCounts
      (s1 + s2)
      (i1 `addNatMaps` i2)
      (d1 `addNatMaps` d2)
      (u1 `addNatMaps` u2)
    where
      addNatMaps = Map.unionWith (+)

instance Monoid SQLOperationCounts where
  mempty = SQLOperationCounts 0 mempty mempty mempty

{- | Add counting of SQL operations to the interpreter of an 'Opaleye' effect.
Note that the effect itself is not actually interpreted. After updating our t'SQLOperationCounts' state
 based on the 'Opaleye' constructor, we then pass them
through to the upstream handler (e.g. 'Bluefin.Opaleye.runOpaleyeWithConnection' or
'Bluefin.Opaleye.runOpaleyeConnection'). See 'Bluefin.Opaleye.runOpaleyeConnectionCounting'
and 'Bluefin.Opaleye.runOpaleyeWithConnectionCounting' for interpreters that do both.

Note: this function should only be used once, otherwise the operations will be tallied
more than once. Unless you're sure, it's probably better to use
'Bluefin.Opaleye.runOpaleyeConnectionCounting' or
'Bluefin.Opaleye.runOpaleyeWithConnectionCounting'.
-}
opaleyeAddCounting ::
  forall es e1 e2 a.
  (e1 :> es, e2 :> es) =>
  State SQLOperationCounts e1 ->
  Opaleye e2 ->
  (forall e. Opaleye e -> Eff (e :& es) a) ->
  Eff es a
opaleyeAddCounting st oldEffect k =
  useImplIn
    k
    MkOpaleye
      { runSelectExplicitImpl = \ff sel -> do
          incrementSelect
          runSelectExplicit oldEffect ff sel
      , runSelectFoldExplicitImpl = \ff sel b f -> do
          incrementSelect
          runSelectFoldExplicit oldEffect ff sel b (\b' -> useImpl . f b')
      , runInsertImpl = \ins -> do
          incrementInsert $ insertTableName ins
          runInsert oldEffect ins
      , runDeleteImpl = \del -> do
          incrementDelete $ deleteTableName del
          runDeleteImpl (mapHandle oldEffect) del
      , runUpdateImpl = \upd -> do
          incrementUpdate $ updateTableName upd
          runUpdate oldEffect upd
      }
  where
    incrementSelect :: Eff (e :& es) ()
    incrementSelect = modify st $ \counts ->
      counts {sqlSelects = succ $ sqlSelects counts}

    incrementInsert :: QualifiedIdentifier -> Eff (e :& es) ()
    incrementInsert name = modify st $ \counts ->
      counts {sqlInserts = incrementMap name $ sqlInserts counts}

    incrementUpdate :: QualifiedIdentifier -> Eff (e :& es) ()
    incrementUpdate name = modify st $ \counts ->
      counts {sqlUpdates = incrementMap name $ sqlUpdates counts}

    incrementDelete :: QualifiedIdentifier -> Eff (e :& es) ()
    incrementDelete name = modify st $ \counts ->
      counts {sqlDeletes = incrementMap name $ sqlDeletes counts}

    incrementMap :: QualifiedIdentifier -> Map QualifiedIdentifier Natural -> Map QualifiedIdentifier Natural
    incrementMap = Map.alter (Just . maybe 1 succ)

-- | This allows us to count the number of SQL operations over the course of a sub-operation.
withCounts ::
  (e :> es) =>
  State SQLOperationCounts e ->
  Eff es a ->
  Eff es (SQLOperationCounts, a)
withCounts st eff = do
  countsBefore <- get st
  res <- eff
  countsAfter <- get st
  pure (countsAfter `subtractCounts` countsBefore, res)

subtractNat :: Natural -> Natural -> Natural
a `subtractNat` b = if a > b then a - b else 0

subtractNatMaps :: (Ord k) => Map k Natural -> Map k Natural -> Map k Natural
subtractNatMaps c1 c2 =
  let f op count = Map.adjust (`subtractNat` count) op
  in  Map.foldrWithKey f c1 c2

subtractCounts :: SQLOperationCounts -> SQLOperationCounts -> SQLOperationCounts
subtractCounts (SQLOperationCounts s1 i1 d1 u1) (SQLOperationCounts s2 i2 d2 u2) =
  SQLOperationCounts
    (s1 `subtractNat` s2)
    (i1 `subtractNatMaps` i2)
    (d1 `subtractNatMaps` d2)
    (u1 `subtractNatMaps` u2)

------------------------------------------------------------
-- Getting table identifiers from opaleye operations

tableIdentifierToQualifiedIdentifier :: O.TableIdentifier -> QualifiedIdentifier
tableIdentifierToQualifiedIdentifier (O.TableIdentifier mSchema table) =
  QualifiedIdentifier (T.pack <$> mSchema) (T.pack table)

insertTableName :: O.Insert haskells -> QualifiedIdentifier
insertTableName (O.Insert table _ _ _) =
  tableIdentifierToQualifiedIdentifier . O.tableIdentifier $ table

updateTableName :: O.Update haskells -> QualifiedIdentifier
updateTableName (O.Update table _ _ _) =
  tableIdentifierToQualifiedIdentifier . O.tableIdentifier $ table

deleteTableName :: O.Delete haskells -> QualifiedIdentifier
deleteTableName (O.Delete table _ _) =
  tableIdentifierToQualifiedIdentifier . O.tableIdentifier $ table

------------------------------------------------------------
-- Pretty rendering and printing counts

instance P.Pretty SQLOperationCounts where
  pPrint = prettyCounts

{- | Print an t'SQLOperationCounts' to stdout using 'prettyCounts'.
For less verbose output, see 'printCountsBrief'.
-}
printCounts :: (MonadIO m) => SQLOperationCounts -> m ()
printCounts = liftIO . putStrLn . renderCounts

{- | Print an t'SQLOperationCounts' to stdout using 'prettyCountsBrief'.
For more verbose output, see 'printCounts'.
-}
printCountsBrief :: (MonadIO m) => SQLOperationCounts -> m ()
printCountsBrief = liftIO . putStrLn . renderCountsBrief

{- | Render an t'SQLOperationCounts' using 'prettyCounts'.
For less verbose output, see 'renderCountsBrief'.

For more control over how the 'P.Doc' gets rendered, use 'P.renderStyle' with a custom 'P.style'.
-}
renderCounts :: SQLOperationCounts -> String
renderCounts = P.render . prettyCounts

{- | Render an t'SQLOperationCounts' using 'prettyCountsBrief'.
For more verbose output, see 'renderCounts'.

For more control over how the 'P.Doc' gets rendered, use 'P.renderStyle' with a custom 'P.style'.
-}
renderCountsBrief :: SQLOperationCounts -> String
renderCountsBrief = P.render . prettyCountsBrief

{- | Pretty-print an t'SQLOperationCounts' using "Text.PrettyPrint".
For each 'Map', we'll print one line for each table. For less verbose output,
see 'prettyCountsBrief'.

This is also the implementation of 'P.pPrint' for t'SQLOperationCounts'.
-}
prettyCounts :: SQLOperationCounts -> P.Doc
prettyCounts = prettyCountsWith $ \mp ->
  let counts = Map.toList mp
      renderPair (name, count) = prefix (renderTableName name) <$> renderNat count
  in  fmap (P.vcat . NE.toList) . NE.nonEmpty $ mapMaybe renderPair counts

{- | Pretty-print an t'SQLOperationCounts' using "Text.PrettyPrint".
For each 'Map', we'll print just the sum of the counts. For more verbose output,
see 'prettyCounts'.
-}
prettyCountsBrief :: SQLOperationCounts -> P.Doc
prettyCountsBrief = prettyCountsWith $ \mp ->
  let total = sum $ Map.elems mp
  in  renderNat total

prettyCountsWith :: (Map QualifiedIdentifier Natural -> Maybe P.Doc) -> SQLOperationCounts -> P.Doc
prettyCountsWith renderMap (SQLOperationCounts selects inserts deletes updates) =
  let parts =
        catMaybes
          [ prefix "SELECT" <$> renderNat selects
          , prefix "INSERT" <$> renderMap inserts
          , prefix "UPDATE" <$> renderMap updates
          , prefix "DELETE" <$> renderMap deletes
          ]
  in  case parts of
        [] -> "None"
        _ -> P.vcat parts

prefix :: P.Doc -> P.Doc -> P.Doc
prefix t n = t P.<> ":" P.<+> n

renderNat :: Natural -> Maybe P.Doc
renderNat = \case
  0 -> Nothing
  n -> Just $ P.pPrint @Integer $ toInteger n

renderTableName :: QualifiedIdentifier -> P.Doc
renderTableName (QualifiedIdentifier mSchema table) =
  case mSchema of
    Nothing -> renderText table
    Just schema -> renderText schema <> "." <> renderText table

renderText :: T.Text -> P.Doc
renderText = P.text . T.unpack