feat(zstd): replace datadog's zstd with Klauspost's zstd (#1709)

Remove Datadog's ZSTD that requires CGO
Make Klauspost's ZSTD as default

README.md

@@ -58,8 +58,6 @@ $ go get github.com/dgraph-io/badger/v3
 ```
 This will retrieve the library.
 
-##### Note: Badger does not directly use CGO but it relies on https://github.com/DataDog/zstd for compression and it requires gcc/cgo. If you wish to use badger without gcc/cgo, you can run `CGO_ENABLED=0 go get github.com/dgraph-io/badger/v3` which will download badger with https://github.com/klauspost/compress ZSTD compression which does not require CGO.
-
 #### Installing Badger Command Line Tool
 
 Download and extract the latest Badger DB release from https://github.com/dgraph-io/badger/releases and then run the following commands.

go.mod

@@ -5,7 +5,6 @@ go 1.12
 // replace github.com/dgraph-io/ristretto => /home/amanbansal/go/src/github.com/dgraph-io/ristretto
 
 require (
-	github.com/DataDog/zstd v1.4.6-0.20210216161059-8cb8bacba7ba
 	github.com/cespare/xxhash v1.1.0
 	github.com/dgraph-io/ristretto v0.0.4-0.20210504190834-0bf2acd73aa3
 	github.com/dustin/go-humanize v1.0.0

go.sum

@@ -1,7 +1,5 @@
 cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
-github.com/DataDog/zstd v1.4.6-0.20210216161059-8cb8bacba7ba h1:3qB2yylqW3kVPr9QoPZtTJOXsJOUdNWT2CrZcifhs5g=
-github.com/DataDog/zstd v1.4.6-0.20210216161059-8cb8bacba7ba/go.mod h1:g4AWEaM3yOg3HYfnJ3YIawPnVdXJh9QME85blwSAmyw=
 github.com/OneOfOne/xxhash v1.2.2 h1:KMrpdQIwFcEqXDklaen+P1axHaj9BSKzvpUUfnHldSE=
 github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=
 github.com/armon/consul-api v0.0.0-20180202201655-eb2c6b5be1b6/go.mod h1:grANhF5doyWs3UAsr3K4I6qtAmlQcZDesFNEHPZAzj8=

options.go

@@ -163,7 +163,7 @@ func DefaultOptions(path string) Options {
 		// compression is ratio supposed to increase with increasing compression level but since the
 		// input for compression algorithm is small (4 KB), we don't get significant benefit at
 		// level 3.
-		// NOTE: The benchmarks are with DataDog ZSTD that requires CGO.
+		// NOTE: The benchmarks are with DataDog ZSTD that requires CGO. Hence, no longer valid.
 		// no_compression-16              10	 502848865 ns/op	 165.46 MB/s	-
 		// zstd_compression/level_1-16     7	 739037966 ns/op	 112.58 MB/s	2.93
 		// zstd_compression/level_3-16     7	 756950250 ns/op	 109.91 MB/s	2.72
@@ -730,7 +730,7 @@ func (opt Options) WithInMemory(b bool) Options {
 // algorithm is small (4 KB), we don't get significant benefit at level 3. It is advised to write
 // your own benchmarks before choosing a compression algorithm or level.
 //
-// NOTE: The benchmarks are with DataDog ZSTD that requires CGO.
+// NOTE: The benchmarks are with DataDog ZSTD that requires CGO. Hence, no longer valid.
 // no_compression-16              10	 502848865 ns/op	 165.46 MB/s	-
 // zstd_compression/level_1-16     7	 739037966 ns/op	 112.58 MB/s	2.93
 // zstd_compression/level_3-16     7	 756950250 ns/op	 109.91 MB/s	2.72

y/zstd_nocgo.go → y/zstd.go

@@ -1,5 +1,3 @@
-// +build !cgo
-
 /*
  * Copyright 2019 Dgraph Labs, Inc. and Contributors
  *