add feature flag to enable ZSTD_STATIC_LINKING_ONLY

Author: zaidoon1

Cargo.toml

@@ -33,6 +33,7 @@ mt_static = ["rust-librocksdb-sys/mt_static"]
 multi-threaded-cf = []
 serde1 = ["serde"]
 malloc-usable-size = ["rust-librocksdb-sys/malloc-usable-size"]
+zstd-static-linking-only = ["rust-librocksdb-sys/zstd-static-linking-only"]
 
 [dependencies]
 libc = "0.2"

README.md

@@ -103,3 +103,12 @@ supported by the platform and is necessary if you want to use the
 malloc_usable_size being available. See
 [rocksdb](https://github.com/facebook/rocksdb/blob/v9.0.0/include/rocksdb/table.h#L401-L434)
 for more information on the feature.
+
+### ZSTD Static Linking Only
+
+The feature `zstd-static-linking-only` in combination with enabling zstd
+compression will cause Rocksdb to hold digested dictionaries in block cache to
+save repetitive deserialization overhead. This saves a lot of CPU for read-heavy
+workloads. This feature is gated behind a flag in Rocksdb because one of the
+digested dictionary APIs used is marked as experimental. However, this feature
+is still used at facebook in production per the [Preset Dictionary Compression Blog Post](https://rocksdb.org/blog/2021/05/31/dictionary-compression.html).

librocksdb-sys/Cargo.toml

@@ -40,6 +40,7 @@ zlib = ["libz-sys"]
 bzip2 = ["bzip2-sys"]
 rtti = []
 malloc-usable-size = []
+zstd-static-linking-only = []
 
 [dependencies]
 libc = "0.2"

librocksdb-sys/build.rs

@@ -75,6 +75,10 @@ fn build_rocksdb() {
         if let Some(path) = env::var_os("DEP_ZSTD_INCLUDE") {
             config.include(path);
         }
+
+        if cfg!(feature = "zstd-static-linking-only") {
+            config.define("ZSTD_STATIC_LINKING_ONLY", Some("1"));
+        }
     }
 
     if cfg!(feature = "zlib") {