improve the Unique Identifier section

Author: dimitri-yatsenko

book/30-schema-design/025-uuid.ipynb

@@ -4,7 +4,25 @@
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-    "# Using UUIDs\n",
+    "# Unique Identifiers\n",
+    "\n",
+    "It is often becomes necessary to assign unique identifiers to entities in a database as *surragate primary key* values. There are many schemes for generating such identifiers.\n",
+    "One of the most common approaches in simple cases is an autoincrementing integer field. Most SQL databases support this with built-in features such as `AUTO_INCREMENT` in MySQL or `SERIAL` in PostgreSQL. It's simple and fast.\n",
+    "\n",
+    "However, autoincrementing ids are not suitable for large distributed systems such as social media platforms (e.g. Instagram). It may be helpful to generate unique identifiers that do not require a database connection or a round-trip to the server.\n",
+    "\n",
+    "\n",
+    "Reading: \n",
+    "* Various Unique Identifiers: https://osamadev.medium.com/understanding-unique-identifiers-uid-uuid-guid-cuid-and-nano-id-3ef2d104ecdf\n",
+    "* UUIDs: https://en.wikipedia.org/wiki/Universally_unique_identifier\n",
+    "* NANOID: https://github.com/ai-sdk/nanoid-python\n",
+    "* NANOID Collision Calculator:https://zelark.github.io/nano-id-cc/\n",
+    "* Sharding IDs at Instagram: https://instagram-engineering.com/sharding-ids-at-instagram-1cf5a71e5a5c\n",
+    "* ULID: https://medium.com/@juniooor/ulid-universally-unique-lexicographically-sortable-identifier-5544e3391660\n",
+    "* ULID: https://github.com/ulid/spec\n",
+    "\n",
+    "\n",
+    "## Universally Unique Identifiers (UUIDs)\n",
     "\n",
     "Universally Unique Identifiers (UUIDs) provide a convenient mechanism for generating unique identifiers for entities inside an information system. The use of UUIDs is standardized by as RFC 4122.\n",
     "\n",
@@ -26,7 +44,7 @@
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@@ -1764,7 +1782,7 @@
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@@ -1778,7 +1796,7 @@
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