rocksdb: remove get_compression_level_number

Signed-off-by: Cholerae Hu <huyingqian@pingcap.com>

src/rocksdb_options.rs

@@ -413,13 +413,10 @@ impl Options {
         }
     }
 
-    pub fn get_compression_level_number(&self) -> usize {
-        unsafe { crocksdb_ffi::crocksdb_options_get_compression_level_number(self.inner) as usize }
-    }
-
     pub fn get_compression_per_level(&self) -> Vec<DBCompressionType> {
-        let size = self.get_compression_level_number();
         unsafe {
+            let size =
+                crocksdb_ffi::crocksdb_options_get_compression_level_number(self.inner) as usize;
             let mut ret = Vec::with_capacity(size);
             let pret = ret.as_mut_ptr();
             crocksdb_ffi::crocksdb_options_get_compression_per_level(self.inner, pret);

tests/test_rocksdb_options.rs

@@ -366,9 +366,13 @@ fn test_get_compression_per_level() {
     let mut opts = Options::new();
     let compressions = &[DBCompressionType::DBNo, DBCompressionType::DBSnappy];
     opts.compression_per_level(compressions);
-    assert_eq!(opts.get_compression_level_number(), 2);
     let v = opts.get_compression_per_level();
     assert_eq!(v.len(), 2);
     assert_eq!(v[0], DBCompressionType::DBNo);
     assert_eq!(v[1], DBCompressionType::DBSnappy);
+    let mut opts2 = Options::new();
+    let empty: &[DBCompressionType] = &[];
+    opts2.compression_per_level(empty);
+    let v2 = opts2.get_compression_per_level();
+    assert_eq!(v2.len(), 0);
 }