server: tune ghc unfolding/specialization flags for performance (closes #2610)

PR-URL: https://github.com/hasura/graphql-engine-mono/pull/2629
GitOrigin-RevId: acb22a595cae672bdf5a0303094fb28fc5afcfb3

CHANGELOG.md

@@ -53,6 +53,7 @@ suffix-less versions.  Aliases may be set by both
   of the invocation will be the same otherwise it will be `NULL`.
 - server: support `extensions` field in error responses from action webhook endpoints (fix #4001)
 - server: fix custom-check based permissions for MSSQL (#7429)
+- server: query performance improvements
 - server: remove identity notion for table columns (fix #7557)
 - server: support MSSQL transactions
 - server: log individual operation details in the http-log during a batch graphQL query execution

cabal.project

@@ -21,6 +21,9 @@ constraints:
   setup.Cabal <3.4
 
 package *
+  -- NOTE: this gets applied to both local (hasura) packages and dependencies,
+  -- but optimizations for local hasura packages are overridden/controlled
+  -- via the 'optimize-hasura' flag.
   optimization: 2
   -- For tooling, e.g. 'weeder', and IDE-like stuff:
   ghc-options: -fwrite-ide-info

cabal.project.ci.local

@@ -11,6 +11,9 @@ package *
     -- the 16G of available memory.
     +RTS -M15000m -RTS
 
+-- Enable optimizations in all local (hasura) packages:
+flags: +optimize-hasura
+
 package graphql-engine
   ghc-options:
     -Werror
@@ -28,7 +31,7 @@ package graphql-engine
 
 package graphql-engine-pro
   ghc-options:
-    -O2 -Werror
+    -Werror
     -- Tune for the circleci `2xlarge` resource class, which provides
     -- 16 vcpus.
     -j14

cabal.project.dev-sh.local

@@ -12,12 +12,12 @@ package *
   -- a massive rebuild. To start, see:
   --   https://www.haskell.org/ghc/blog/20200403-dwarf-1.html
   debug-info: 2
+  
+-- NOTE: new-build may report a misleading 'Build profile: -O1'
+-- See:https://github.com/haskell/cabal/issues/6221
+flags: -optimize-hasura
 
 package graphql-engine
-  -- NOTE: this seems to work so long as there is no 'ghc-options: -O2' in the cabal file,
-  -- but new-build will report 'Build profile: -O1' for some reason.
-  -- See:https://github.com/haskell/cabal/issues/6221
-  optimization: 0
   documentation: false
   flags: +developer
   -- NOTE: 'cabal new-build --enable-coverage' seems to rebuild all deps with coverage

server/graphql-engine.cabal

@@ -25,16 +25,38 @@ flag profiling
   default: False
   manual: True
 
+-- A single flag to enable all optimization-related settings at once, for all
+-- hasura code.
+-- We share this flag name across our .cabal projects so we can switch it on or
+-- off for all of them at the top level of our cabal.project(.*) files
+flag optimize-hasura
+  description: Compile hasura code with appropriate optimizations 
+  default: True
+  manual: False
+
 common common-all
   ghc-options:
-    -fmax-simplifier-iterations=20 -foptimal-applicative-do
+    -foptimal-applicative-do
     -Wall -Wcompat -Wincomplete-record-updates -Wincomplete-uni-patterns -Wredundant-constraints
+    -- This is just to keep compile-times in check and might be adjusted later (See mono #2610):
+    -fmax-simplifier-iterations=2
 
   if flag(developer)
     cpp-options: -DDeveloperAPIs
   if flag(profiling)
     cpp-options: -DPROFILING
 
+  if flag(optimize-hasura)
+    ghc-options:
+      -- This is for performance, and works in combination with '-fspecialise-aggressively' 
+      -- in the graphql-engine 'executable' stanza below, and in any other dependent 
+      -- executables (See mono #2610):
+      -fexpose-all-unfoldings
+      -O2
+  else
+    -- we just want to build fast:
+    ghc-options: -O0
+
   default-language: Haskell2010
   default-extensions:
     AllowAmbiguousTypes
@@ -659,6 +681,12 @@ library
 
 executable graphql-engine
   import: common-all, common-exe
+
+  if flag(optimize-hasura)
+    ghc-options:
+      -- This is for performance (See mono #2610):
+      -fspecialise-aggressively
+       
   hs-source-dirs:    src-exec
   main-is:           Main.hs
   build-depends:     base

server/src-exec/Main.hs

@@ -1,7 +1,7 @@
 {-# LANGUAGE NamedFieldPuns #-}
 {-# LANGUAGE RecordWildCards #-}
 
-module Main where
+module Main (main) where
 
 import Control.Concurrent.Extended qualified as C
 import Control.Exception