refactor(compaction): rename skip_some to add and update implementation

pageserver/compaction/src/compact_tiered.rs

@@ -714,7 +714,7 @@ impl<K: CompactionKey> KeyspaceWindowPos<K> {
                 self.accum_keysize += distance as u64;
             } else {
                 // advance within the range
-                let skip_key = self.end_key.skip_some();
+                let skip_key = self.end_key.add(128);
                 let distance = K::key_range_size(&(self.end_key..skip_key), shard_identity);
                 if (self.accum_keysize + distance as u64) < max_size {
                     self.end_key = skip_key;

pageserver/compaction/src/interface.rs

@@ -109,10 +109,8 @@ pub trait CompactionKey: std::cmp::Ord + Clone + Copy + std::fmt::Display {
     // return "self + 1"
     fn next(&self) -> Self;
 
-    // return "self + <some decent amount to skip>". The amount to skip
-    // is left to the implementation.
-    // FIXME: why not just "add(u32)" ?  This is hard to use
-    fn skip_some(&self) -> Self;
+    // return "self + offset"
+    fn add(&self, offset: u32) -> Self;
 }
 
 impl CompactionKey for Key {
@@ -125,8 +123,8 @@ impl CompactionKey for Key {
     fn next(&self) -> Key {
         (self as &Key).next()
     }
-    fn skip_some(&self) -> Key {
-        self.add(128)
+    fn add(&self, offset: u32) -> Key {
+        (self as &Key).add(offset)
     }
 }
 

pageserver/compaction/src/simulator.rs

@@ -75,9 +75,8 @@ impl interface::CompactionKey for Key {
     fn next(&self) -> Self {
         self + 1
     }
-    fn skip_some(&self) -> Self {
-        // round up to next xx
-        self + 100
+    fn add(&self, offset: u32) -> Self {
+        self + offset as u64
     }
 }