fix unique constraint on relational session data. Closes #4183

prisma/migrations/23_update_session_data/migration.sql

@@ -0,0 +1,16 @@
+WITH ranked_session_data AS (
+  SELECT
+    "session_data_id",
+    ROW_NUMBER() OVER (
+      PARTITION BY "session_id", "data_key"
+      ORDER BY "created_at" DESC NULLS LAST, "session_data_id" DESC
+    ) AS row_num
+  FROM "session_data"
+)
+DELETE FROM "session_data"
+USING ranked_session_data
+WHERE "session_data"."session_data_id" = ranked_session_data."session_data_id"
+  AND ranked_session_data.row_num > 1;
+
+CREATE UNIQUE INDEX "session_data_session_id_data_key_key"
+ON "session_data"("session_id", "data_key");