postgresql: support JIT compilation for version >= 11

[andir]

Motivation for this change

PostgreSQL (from 11 onwards AFAICT) supports JIT compilation of
(frequently used) queries. This should provide a speedup to some queries
where operations such as comparing rows is a bottleneck.

For JIT support we have to build PostgreSQL with with the --with-llvm
config flag and pass both clang and llvm into the build environment.
PostPostgreSQL then calls llvm-config to obtain the required compiler
flags.

Things done

• compiled postgresl 11 with the feature
• tested that JIT actually works
• verify that all the postgresql version we provide still build

[andir]

I've changed the postgresql test to verify that JIT is working (through the plan analyzer) and that it does still return the right results (by running a query with JIT being on).

[marsam]

Thanks for working on this.
You may be interested in the previous attempt #38698, specifically in commits dcd9455 8caf523 91841ff

[risicle]

Did a dirty cherry-pick of this to master so I could build it (in <24h) and I get a failure on macos 10.15:

...
gzipping man pages under /nix/store/cyj6isr81b41a7269jzrdc5467xy9zbn-postgresql-11.11-man/share/man/
strip is /nix/store/9xawf09c90761xkxv8r1b55ja46x4wr3-cctools-binutils-darwin-949.0.1/bin/strip
patching script interpreter paths in /nix/store/cyj6isr81b41a7269jzrdc5467xy9zbn-postgresql-11.11-man
output '/nix/store/g4k7qcs7fff5vn34msn8kyq7mmsqyfh2-postgresql-11.11' is not allowed to refer to the following paths:
  /nix/store/d4p8v32sivk3zj3jklx3irswbwwigxcd-clang-wrapper-7.1.0
error: build of '/nix/store/rzimpd88ysc69x39m437kx3k9vm2y1aq-postgresql-11.11.drv' failed

[andir]

Did a dirty cherry-pick of this to master so I could build it (in <24h) and I get a failure on macos 10.15:

...
gzipping man pages under /nix/store/cyj6isr81b41a7269jzrdc5467xy9zbn-postgresql-11.11-man/share/man/
strip is /nix/store/9xawf09c90761xkxv8r1b55ja46x4wr3-cctools-binutils-darwin-949.0.1/bin/strip
patching script interpreter paths in /nix/store/cyj6isr81b41a7269jzrdc5467xy9zbn-postgresql-11.11-man
output '/nix/store/g4k7qcs7fff5vn34msn8kyq7mmsqyfh2-postgresql-11.11' is not allowed to refer to the following paths:
  /nix/store/d4p8v32sivk3zj3jklx3irswbwwigxcd-clang-wrapper-7.1.0
error: build of '/nix/store/rzimpd88ysc69x39m437kx3k9vm2y1aq-postgresql-11.11.drv' failed

Likely fixable with some of the commits that @marsam mentioned above. I'll try to get to them soon.

[dasJ]

Yes they found a solution:

     # JIT is only supported on Linux, for now. (Darwin may build, but must be
     # tested).
     jitEnabled = atLeast "11" && enableJitSupport && deps.stdenv.isLinux;

[dasJ]

This is what I did in my overlay so the closure doesn't grow too much (not a whole gigabyte). Parts of these are stolen from the old PR.
There is no runtime dependency on cc anymore.

self: super: {
  postgresql_13 = (super.postgresql_13.overrideAttrs (oA: {
    nativeBuildInputs = (oA.nativeBuildInputs or []) ++ [ super.llvmPackages_latest.llvm super.nukeReferences super.patchelf ];
    configureFlags = (oA.configureFlags or []) ++ [ "--with-llvm" ];
    postPatch = ''
      ${oA.postPatch or ""}

      # Force lookup of jit stuff in $out instead of $lib
      substituteInPlace src/backend/jit/jit.c --replace pkglib_path \"$out/lib\"
      substituteInPlace src/backend/jit/llvm/llvmjit.c --replace pkglib_path \"$out/lib\"
      substituteInPlace src/backend/jit/llvm/llvmjit_inline.cpp --replace pkglib_path \"$out/lib\"
    '';

    postInstall = ''
      ${oA.postInstall or ""}

      # Move the bitcode and libllvmjit.so library out of $lib; otherwise, every client that
      # depends on libpq.so will also have libLLVM.so in its closure too, bloating it
      moveToOutput "lib/bitcode" "$out"
      moveToOutput "lib/llvmjit*" "$out"

      # In the case of JIT support, prevent a retained dependency on clang-wrapper
      substituteInPlace "$out/lib/pgxs/src/Makefile.global" --replace ${super.llvmPackages_latest.stdenv.cc}/bin/clang clang
      nuke-refs $out/lib/llvmjit_types.bc $(find $out/lib/bitcode -type f)

      # Stop out depending on the default output of llvm
      substituteInPlace $out/lib/pgxs/src/Makefile.global \
        --replace ${super.llvmPackages_latest.llvm.out}/bin "" \
        --replace '$(LLVM_BINPATH)/' ""

      # Stop out depending on the -dev output of llvm
      substituteInPlace $out/lib/pgxs/src/Makefile.global \
        --replace ${super.llvmPackages_latest.llvm.dev}/bin/llvm-config llvm-config \
        --replace -I${super.llvmPackages_latest.llvm.dev}/include ""

      # Stop lib depending on the -dev output of llvm
      rpath=$(patchelf --print-rpath $out/lib/llvmjit.so)
      nuke-refs -e $out $out/lib/llvmjit.so
      # Restore the correct rpath
      patchelf $out/lib/llvmjit.so --set-rpath "$rpath"
    '';
  })).override {
    stdenv = super.llvmPackages_latest.stdenv;
  };
}

Size comparison

	No JIT	JIT	Diff
out size	25M	97M	+72M
out closure size	305.3M	693.4M	+388.1M
lib size	6.0M	5.9M	-0.1M
lib closure size	46.7M	46.5M	-0.2M

New dependencies of out

• /nix/store/f3qba2h3b9krj1ir343f9r8m73by5rn3-llvm-11.1.0-lib
• /nix/store/niplk2w8g0ri0n8h07zyp1l3cbnzv7a2-glibc-2.32-46-dev

[stale]

I marked this as stale due to inactivity. → More info

[RaitoBezarius]

Can I do something to get this merged? It is an awesome feature.

[risicle]

Agreed. I think #150801 was the most recent attempt at this, which I think stalled a bit deciding whether we needed a nixos test for this and if we therefore needed a postgresqlJit package. I would personally vote yes on both counts, otherwise we'll never discover it breaking.