fix dict copy performance

Author: sid42

contracts/TopShotIPFSResolver.cdc

@@ -3,12 +3,23 @@ access(all) contract TopShotIPFSResolver {
     access(all) event CIDSet(setID: UInt32, playID: UInt32, subeditionID: UInt32, mediaType: String, cid: String)
     access(all) event GatewayUpdated(gateway: String)
 
-    // Number of buckets to split CID entries across
     access(all) let numBuckets: UInt64
 
-    // Sharded storage: bucket index -> composite key -> { mediaType: CID }
-    // Let's us store 32 * 100k = 32M CID entries
-    access(contract) let shards: {UInt64: {String: {String: String}}}
+    // Each shard is a resource stored at its own path so writes
+    // borrow a reference and mutate in place — no dict copy.
+    access(all) resource Shard {
+        access(all) let entries: {String: {String: String}}
+
+        init() {
+            self.entries = {}
+        }
+
+        access(contract) fun setCID(key: String, mediaType: String, cid: String) {
+            var inner = self.entries[key] ?? {}
+            inner[mediaType] = cid
+            self.entries[key] = inner
+        }
+    }
 
     // IPFS gateway base URL (e.g., "https://ipfs.dapperlabs.com/ipfs/")
     access(all) var gateway: String
@@ -19,25 +30,56 @@ access(all) contract TopShotIPFSResolver {
         access(all) fun setCID(setID: UInt32, playID: UInt32, subeditionID: UInt32, mediaType: String, cid: String) {
             let key = TopShotIPFSResolver.buildKey(setID: setID, playID: playID, subeditionID: subeditionID)
             let bucket = TopShotIPFSResolver.getBucket(setID: setID, playID: playID, subeditionID: subeditionID)
-            var shard = TopShotIPFSResolver.shards[bucket] ?? {}
-            var inner = shard[key] ?? {}
-            inner[mediaType] = cid
-            shard[key] = inner
-            TopShotIPFSResolver.shards[bucket] = shard
+            let shard = TopShotIPFSResolver.borrowShard(bucket)
+            shard.setCID(key: key, mediaType: mediaType, cid: cid)
             emit CIDSet(setID: setID, playID: playID, subeditionID: subeditionID, mediaType: mediaType, cid: cid)
         }
 
         access(all) fun setGateway(gateway: String) {
             TopShotIPFSResolver.gateway = gateway
             emit GatewayUpdated(gateway: gateway)
         }
+
+        access(all) fun clearAllCIDs() {
+            var i: UInt64 = 0
+            while i < TopShotIPFSResolver.numBuckets {
+                let path = TopShotIPFSResolver.shardPath(i)
+                if let existing <- TopShotIPFSResolver.account.storage.load<@Shard>(from: path) {
+                    destroy existing
+                }
+                i = i + 1
+            }
+        }
     }
 
     access(all) view fun getCIDs(setID: UInt32, playID: UInt32, subeditionID: UInt32): {String: String}? {
         let key = self.buildKey(setID: setID, playID: playID, subeditionID: subeditionID)
         let bucket = self.getBucket(setID: setID, playID: playID, subeditionID: subeditionID)
-        let shard = self.shards[bucket] ?? {}
-        return shard[key]
+        let path = self.shardPath(bucket)
+        if let shard = self.account.storage.borrow<&Shard>(from: path) {
+            if let entry = shard.entries[key] {
+                // Return a copy, not a reference
+                let result: {String: String} = {}
+                for mediaType in entry.keys {
+                    result[mediaType] = entry[mediaType]
+                }
+                return result
+            }
+        }
+        return nil
+    }
+
+    access(contract) fun borrowShard(_ bucket: UInt64): &Shard {
+        let path = self.shardPath(bucket)
+        if let shard = self.account.storage.borrow<&Shard>(from: path) {
+            return shard
+        }
+        self.account.storage.save(<- create Shard(), to: path)
+        return self.account.storage.borrow<&Shard>(from: path)!
+    }
+
+    access(all) view fun shardPath(_ bucket: UInt64): StoragePath {
+        return StoragePath(identifier: "TopShotIPFSShard_".concat(bucket.toString()))!
     }
 
     access(all) view fun getBucket(setID: UInt32, playID: UInt32, subeditionID: UInt32): UInt64 {
@@ -53,8 +95,7 @@ access(all) contract TopShotIPFSResolver {
     }
 
     init() {
-        self.numBuckets = 32
-        self.shards = {}
+        self.numBuckets = 31
         self.gateway = "https://ipfs.dapperlabs.com/ipfs/"
         self.AdminStoragePath = /storage/TopShotIPFSResolverAdmin
         self.account.storage.save<@Admin>(<- create Admin(), to: self.AdminStoragePath)