Fix column distinct

src/main/kotlin/io/github/wulkanowy/schools/dao/DistinctOn.kt

@@ -0,0 +1,24 @@
+package io.github.wulkanowy.schools.dao
+
+import org.jetbrains.exposed.sql.BooleanColumnType
+import org.jetbrains.exposed.sql.CustomFunction
+import org.jetbrains.exposed.sql.Expression
+import org.jetbrains.exposed.sql.QueryBuilder
+
+fun customDistinctOn(vararg expressions: Expression<*>): CustomFunction<Boolean?> = customBooleanFunction(
+    functionName = "DISTINCT ON",
+    postfix = " TRUE",
+    params = expressions
+)
+
+fun customBooleanFunction(
+    functionName: String, postfix: String = "", vararg params: Expression<*>
+): CustomFunction<Boolean?> =
+    object : CustomFunction<Boolean?>(functionName, BooleanColumnType(), *params) {
+        override fun toQueryBuilder(queryBuilder: QueryBuilder) {
+            super.toQueryBuilder(queryBuilder)
+            if (postfix.isNotEmpty()) {
+                queryBuilder.append(postfix)
+            }
+        }
+    }

src/main/kotlin/io/github/wulkanowy/schools/dao/LoginEventDao.kt

@@ -29,8 +29,11 @@ class LoginEventDao {
         order: SortOrder?,
     ): List<LoginEvent> = dbQuery {
         LoginEvents
+            .slice(
+                customDistinctOn(LoginEvents.schoolId, LoginEvents.symbol, LoginEvents.scraperBaseUrl),
+                *(LoginEvents.columns).toTypedArray()
+            )
             .selectAll()
-            .groupBy(LoginEvents.schoolId, LoginEvents.symbol, LoginEvents.scraperBaseUrl)
             .limit(pageSize, page * pageSize)
             .let {
                 if (orderBy != null && order != null) {