add correct readme

README.md

@@ -1,6 +1,21 @@
-# exposed-upsert
+# Exposed PostgreSQL Upsert
 ![CI Build Pipeline](https://github.com/LukasForst/exposed-upsert/workflows/CI%20Build%20Pipeline/badge.svg)
 
-PostgreSQL upsert for Exposed framework based on issues.
+Unfortunately, current [Exposed](https://github.com/JetBrains/Exposed) framework does not contain upsert 
+(update or insert) functionality out of the box. 
+This simple extension library provides implementation for PostgreSQL.
+Implementation is based on the comment [Maxr1998](https://github.com/Maxr1998) made
+[here](https://github.com/JetBrains/Exposed/issues/167#issuecomment-480199613).
 
-Implementation based on https://github.com/JetBrains/Exposed/issues/167#issuecomment-480199613
+Usage can be seen for example in [Wire](https://github.com/wireapp/) [Poll Bot](https://github.com/wireapp/poll-bot)
+[here](https://github.com/wireapp/poll-bot/blob/fc74e2ae15691484714efe2b7803dbc5e235da01/src/main/kotlin/com/wire/bots/polls/dao/PollRepository.kt#L49)
+
+Following code tries to insert new value of `optionId` to `Votes` table where `pollId` and `userId` is composite key.
+If the combination `pollId` and `userId` already exist, `optionId` is updated.
+```kotlin
+Votes.insertOrUpdate(Votes.pollId, Votes.userId) {
+    it[pollId] = pollAction.pollId
+    it[pollOption] = pollAction.optionId
+    it[userId] = pollAction.userId
+}
+```