tech(api): add migration for unique index on knowledge-element-snapshot

Author: lionelB

Diff for: api/db/migrations/20250403142506_add-campaign-participation-id-unicity-constraint-on-snapshot.js

@@ -0,0 +1,40 @@
+const TABLE_NAME = 'knowledge-element-snapshots';
+const COLUMN_NAME = 'campaignParticipationId';
+const CONSTRAINT_NAME = 'one_snapshot_by_campaignParticipationId';
+
+/**
+ * @param { import("knex").Knex } knex
+ * @returns { Promise<void> }
+ */
+const up = async function (knex) {
+  const result = await knex.raw(
+    `select constraint_name
+                   from information_schema.constraint_column_usage
+                   where table_name = :tableName  and constraint_name = :constraintName`,
+    {
+      tableName: TABLE_NAME,
+      constraintName: CONSTRAINT_NAME,
+    },
+  );
+
+  if (result.rowCount === 1) {
+    return;
+  }
+  await knex.raw('ALTER TABLE :tableName: ADD CONSTRAINT :constraintName: UNIQUE (:columnName:)', {
+    tableName: TABLE_NAME,
+    constraintName: CONSTRAINT_NAME,
+    columnName: COLUMN_NAME,
+  });
+};
+
+/**
+ * @param { import("knex").Knex } knex
+ * @returns { Promise<void> }
+ */
+const down = async function (knex) {
+  await knex.schema.table(TABLE_NAME, function (table) {
+    table.dropUnique(COLUMN_NAME, CONSTRAINT_NAME);
+  });
+};
+
+export { down, up };