adding code an README

Author: g4lb

.idea/.gitignore

@@ -1 +1,25 @@
-# database-concurrency-control
+# Database Concurrency Control Examples
+
+This repository contains examples of implementing concurrency control mechanisms in Python for managing concurrent access to a shared database. Two commonly used locking mechanisms, pessimistic locking and optimistic locking, are demonstrated in separate code examples.
+
+## Pessimistic Locking Example
+
+The `pessimistic-locking.py` file demonstrates how to implement pessimistic locking in Python using the `threading.Lock` object. Pessimistic locking ensures exclusive access to a shared resource by acquiring a lock before performing write operations. In the example, the `update_user_record` function represents the code that updates a user record in a database. The `Lock` object is used to synchronize access to the user record, allowing only one thread to modify it at a time. This ensures data consistency and prevents conflicts.
+
+To run the pessimistic locking example, execute the following command:
+```
+python pessimistic-locking.py
+```
+
+## Optimistic Locking Example
+
+The `optimistic-locking.py` file demonstrates how to implement optimistic locking in Python using versioning. Optimistic locking assumes that conflicts are rare and allows concurrent access to a shared resource. In the example, the `update_user_record` function represents the code that updates a user record in a database. It reads the current version of the user record and compares it with the stored version. If the versions match, the update operation proceeds; otherwise, a conflict is detected. This approach minimizes the need for locking and allows for better concurrency while still ensuring data integrity.
+
+To run the optimistic locking example, execute the following command:
+```
+python optimistic-locking.py
+```
+
+## Requirements
+
+The code examples require Python 3.x.

.idea/inspectionProfiles/profiles_settings.xml

@@ -0,0 +1,52 @@
+import threading
+import time
+
+# Assume this is the user record in the database
+user = {
+    'id': 1,
+    'name': 'John Doe',
+    'email': 'johndoe@example.com',
+    'age': 30,
+    'version': 1  # Version number for optimistic locking
+}
+
+
+# Function to update the user record
+def update_user_record(user_id, new_name):
+    print(f"Thread {threading.current_thread().name} is attempting to update the user record.")
+
+    # Simulate some processing time
+    time.sleep(2)
+
+    # Read the current version of the user record
+    current_version = user['version']
+
+    # Simulate some more processing time
+    time.sleep(2)
+
+    # Perform the update operation only if the version hasn't changed
+    if current_version == user['version']:
+        # Update the user record
+        user['name'] = new_name
+        user['version'] += 1
+
+        print(f"Thread {threading.current_thread().name} has updated the user record: {user}")
+    else:
+        print(
+            f"Thread {threading.current_thread().name} detected a conflict. The user record has been updated by another thread.")
+
+
+# Create two threads that update the user record simultaneously
+thread1 = threading.Thread(target=update_user_record, args=(1, 'Jane Smith'))
+thread2 = threading.Thread(target=update_user_record, args=(1, 'Alice Johnson'))
+
+# Start the threads
+thread1.start()
+thread2.start()
+
+# Wait for the threads to finish
+thread1.join()
+thread2.join()
+
+# Print the final user record
+print(f"Final user record: {user}")

.idea/misc.xml

@@ -0,0 +1,54 @@
+import threading
+import time
+
+# Assume this is the user record in the database
+user = {
+    'id': 1,
+    'name': 'John Doe',
+    'email': 'johndoe@example.com',
+    'age': 30
+}
+
+# Create a lock object to synchronize access to the user record
+lock = threading.Lock()
+
+
+# Function to update the user record
+def update_user_record(user_id, new_name):
+    print(f"Thread {threading.current_thread().name} is attempting to update the user record.")
+
+    # Acquire the lock to ensure exclusive access to the user record
+    lock.acquire()
+    print(f"Thread {threading.current_thread().name} has acquired the lock.")
+
+    try:
+        # Simulate some processing time
+        time.sleep(2)
+
+        # Perform the update operation
+        user['name'] = new_name
+        print(f"Thread {threading.current_thread().name} has updated the user record: {user}")
+
+        # Simulate some more processing time
+        time.sleep(2)
+
+    finally:
+        # Release the lock to allow other threads to access the user record
+        lock.release()
+        print(f"Thread {threading.current_thread().name} has released the lock.")
+
+
+# Create two threads that update the user record simultaneously
+thread1 = threading.Thread(target=update_user_record, args=(1, 'Jane Smith'))
+thread2 = threading.Thread(target=update_user_record, args=(1, 'Alice Johnson'))
+
+# Start the threads
+thread1.start()
+thread2.start()
+
+# Wait for the threads to finish
+thread1.join()
+thread2.join()
+
+# Print the final user record
+print(f"Final user record: {user}")