{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE QuasiQuotes #-}

module PGExtras.Queries.CacheHit (cacheHitSQL, displayCacheHit) where

import PGExtras.Helpers (maybeText)
import Database.PostgreSQL.Simple
import Text.RawString.QQ
import qualified Data.Text as Text
import Control.Monad (forM_)
import Data.List (intercalate)

cacheHitSQL :: Query
cacheHitSQL :: Query
cacheHitSQL = [r|SELECT
'index hit rate' AS name,
(sum(idx_blks_hit)) / nullif(sum(idx_blks_hit + idx_blks_read),0) AS ratio
FROM pg_statio_user_indexes
UNION ALL
SELECT 'table hit rate' AS name,
sum(heap_blks_hit) / nullif(sum(heap_blks_hit) + sum(heap_blks_read),0) AS ratio
FROM pg_statio_user_tables;|]

displayCacheHit :: [(Maybe Text.Text, Maybe Text.Text)] -> IO ()
displayCacheHit :: [(Maybe Text, Maybe Text)] -> IO ()
displayCacheHit rows :: [(Maybe Text, Maybe Text)]
rows = do
  String -> IO ()
putStrLn (String -> IO ()) -> String -> IO ()
forall a b. (a -> b) -> a -> b
$ String
description
  String -> IO ()
putStrLn (String -> IO ()) -> String -> IO ()
forall a b. (a -> b) -> a -> b
$ String -> [String] -> String
forall a. [a] -> [[a]] -> [a]
intercalate " | " [String]
tableHeaders
  [(Maybe Text, Maybe Text)]
-> ((Maybe Text, Maybe Text) -> IO ()) -> IO ()
forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
t a -> (a -> m b) -> m ()
forM_ [(Maybe Text, Maybe Text)]
rows (((Maybe Text, Maybe Text) -> IO ()) -> IO ())
-> ((Maybe Text, Maybe Text) -> IO ()) -> IO ()
forall a b. (a -> b) -> a -> b
$ \(arg1 :: Maybe Text
arg1, arg2 :: Maybe Text
arg2) ->
    String -> IO ()
putStrLn (String -> IO ()) -> String -> IO ()
forall a b. (a -> b) -> a -> b
$ Maybe Text -> String
maybeText(Maybe Text
arg1) String -> String -> String
forall a. [a] -> [a] -> [a]
++ " | " String -> String -> String
forall a. [a] -> [a] -> [a]
++ Maybe Text -> String
maybeText(Maybe Text
arg2)

description :: [Char]
description :: String
description = "Index and table hit rate"

tableHeaders :: [[Char]]
tableHeaders :: [String]
tableHeaders = ["name", "ratio"]