@todo optimized getAndAdd operations

Author: PicoCreator

src/main/java/picoded/dstack/KeyLongMap.java

@@ -180,39 +180,10 @@ default Long removeValue(Object key) {
 	 **/
 	default Long addAndGet(Object key, Object delta) {
 		//
-		// NOTE : The default implmentation of addAndGet,
-		//        or getAndAdd relies on repetaed tries using
-		//        weakCompareAndSet, while functional.
-		//        Is highly inefficent in most cases
+		// We simply use get and add, with the delta,
+		// this reduce the amount of permutation needed to support
 		//
-		
-		// Validate and convert the key to String
-		if (key == null) {
-			throw new IllegalArgumentException("key cannot be null in addAndGet");
-		}
-		String keyAsString = key.toString();
-		
-		// Attempt to update the key for 5 times before throwing exception
-		for (int tries = 0; tries < 5; tries++) {
-			// Retrieve value from key
-			Long value = getValue(keyAsString);
-			
-			// Assume value as 0 if not exist
-			if (value == null) {
-				value = new Long(0);
-			}
-			
-			// Calculate the updated value
-			Long updatedValue = GenericConvert.toLong(delta) + value;
-			
-			// Update the value with weakCompareAndSet and return 
-			if (weakCompareAndSet(keyAsString, value, updatedValue)) {
-				return updatedValue;
-			}
-		}
-		
-		// Throw exception due to number of retries exceeded the limit
-		throw new RuntimeException("Number of retries exceeded limit for addAndGet");
+		return getAndAdd(key, delta)+GenericConvert.toLong(delta);
 	}
 
 	/**
@@ -233,7 +204,7 @@ default Long getAndAdd(Object key, Object delta) {
 
 		// Validate and convert the key to String
 		if (key == null) {
-			throw new IllegalArgumentException("key cannot be null in addAndGet");
+			throw new IllegalArgumentException("key cannot be null in");
 		}
 		String keyAsString = key.toString();
 
@@ -257,7 +228,7 @@ default Long getAndAdd(Object key, Object delta) {
 		}
 
 		// Throw exception due to number of retries exceeded the limit
-		throw new RuntimeException("Number of retries exceeded limit for addAndGet");
+		throw new RuntimeException("Number of retries exceeded limit");
 	}
 
 	/**

src/main/java/picoded/dstack/mongodb/MongoDB_KeyLongMap.java

@@ -406,6 +406,118 @@ public boolean weakCompareAndSet(String key, Long expect, Long update) {
 		return false;
 	}
 
+	//--------------------------------------------------------------------------
+	//
+	// @TODO : Optimized getAndAdd
+	//
+	//--------------------------------------------------------------------------
+	
+	// /**
+	//  * Returns the value, given the key
+	//  *
+	//  * @param key param find the meta key
+	//  * @param delta value to add
+	//  *
+	//  * @return  value of the given key after adding
+	//  **/
+	// public Long getAndAdd(Object key, Object delta) {
+		
+	// 	// This is the more optimized varient for weakCompareAndSet
+	// 	// ---
+
+	// 	// Validate and convert the key to String
+	// 	if (key == null) {
+	// 		throw new IllegalArgumentException("key cannot be null in");
+	// 	}
+	// 	String keyAsString = key.toString();
+		
+	// 	// Normalize the delta to a long
+	// 	Long deltaLong = GenericConvert.toLong(delta);
+
+	// 	// Configure this to be an "upsert" query
+	// 	FindOneAndUpdateOptions opt = new FindOneAndUpdateOptions();
+	// 	opt.upsert(true);
+
+	// 	// now timestamp
+	// 	Date now = new Date();
+		
+	// 	// Lets generate the mongodb "update" document rule
+	// 	Document updateDoc = new Document();
+		
+	// 	// Disable expire timestamp when using 
+	// 	// weakCompareAndSet/getAndAdd/addAndGet
+	// 	Document unset_doc = new Document();
+	// 	unset_doc.append("expireAt", "");
+	// 	updateDoc.append("$unset", unset_doc);
+		
+	// 	// Setup the value on update/insert/upsert
+	// 	Document inc_doc = new Document();
+	// 	inc_doc.append("val", deltaLong);
+	// 	updateDoc.append("$set", set_doc);
+		
+	// 	//
+	// 	// In general there are the following compare and set scenerios to handle
+	// 	//
+	// 	// 1) expecting value is 0
+	// 	//   a) existing record is expired
+	// 	//   b) existing record does not exist
+	// 	//   c) existing record is NOT expired, and is 0
+	// 	// 2) expecting value is non-zero
+	// 	//   a) existing record is NOT expired, and is expected value.
+	// 	//
+		
+	// 	// Potentially a new upsert, ensure there is something to "update" atleast
+	// 	// initializing an empty row if it does not exist
+	// 	if (expect == null || expect == 0l) {
+	// 		// Expect is now atleast 0
+	// 		expect = 0l;
+	// 	}
+		
+	// 	//
+	// 	// We update any existing values
+	// 	// this handle scenerio 1a, 1c & 2a
+	// 	// 
+	// 	// We can do this safely here, as mongodb handles the expire
+	// 	// natively, so we do not need to worry about race conditions.
+	// 	//
+		
+	// 	//
+	// 	// Upsert the document
+	// 	//
+	// 	Object ret = collection.findOneAndUpdate(Filters.and(Filters.eq("key", key), //
+	// 		Filters.or( //
+	// 			// Handles an expired record
+	// 			Filters.and(Filters.gt("expireAt", new Date(0l)), Filters.lt("expireAt", now)),
+	// 			// Handles an non-expired record
+	// 			Filters.and(Filters.eq("val", expect), filterForUnexpired(now)))), updateDoc, opt);
+		
+	// 	// Return true on succesful update
+	// 	if (ret != null) {
+	// 		return true;
+	// 	}
+		
+	// 	//
+	// 	// We insert a record if possible, this handle sceneric 1b
+	// 	//
+	// 	if (expect == 0l) {
+	// 		try {
+	// 			InsertOneResult res = collection.insertOne( //
+	// 				new Document().append("key", key).append("val", update) //
+	// 				);
+				
+	// 			if (res.wasAcknowledged()) {
+	// 				return true;
+	// 			}
+	// 		} catch (Exception e) {
+	// 			// This is probably due to a conflicting index
+	// 			return false;
+	// 		}
+	// 	}
+		
+	// 	// All Failed
+	// 	return false;
+	// }
+
 	//--------------------------------------------------------------------------
 	//
 	// Remove call