From ee64adf9598fc5bbf0a59a1599f39f0ff1b636fc Mon Sep 17 00:00:00 2001
From: Corie Watson <watson.corie@gmail.com>
Date: Fri, 16 May 2025 01:30:16 +0100
Subject: [PATCH] fix(firestore-bigquery-change-tracker): keep partition value
 on delete using old data

---
 .../src/bigquery/partitioning.ts                     | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/firestore-bigquery-export/firestore-bigquery-change-tracker/src/bigquery/partitioning.ts b/firestore-bigquery-export/firestore-bigquery-change-tracker/src/bigquery/partitioning.ts
index 1d3a468fe..7e309df91 100644
--- a/firestore-bigquery-export/firestore-bigquery-change-tracker/src/bigquery/partitioning.ts
+++ b/firestore-bigquery-export/firestore-bigquery-change-tracker/src/bigquery/partitioning.ts
@@ -1,5 +1,5 @@
 import { FirestoreBigQueryEventHistoryTrackerConfig } from ".";
-import { FirestoreDocumentChangeEvent } from "..";
+import { ChangeType, FirestoreDocumentChangeEvent } from "..";
 import * as firebase from "firebase-admin";
 
 import * as logs from "../logs";
@@ -7,7 +7,6 @@ import * as bigquery from "@google-cloud/bigquery";
 import * as functions from "firebase-functions";
 import { getNewPartitionField } from "./schema";
 import { BigQuery, TableMetadata } from "@google-cloud/bigquery";
-
 import { PartitionFieldType } from "../types";
 
 export class Partitioning {
@@ -195,11 +194,16 @@ export class Partitioning {
     Delete changes events have no data, return early as cannot partition on empty data.
   **/
   getPartitionValue(event: FirestoreDocumentChangeEvent) {
-    if (!event.data) return {};
+    // When old data is disabled and the operation is delete
+    // the data and old data will be null
+    if (event.data === null && event.oldData === null) return {};
 
     const firestoreFieldName = this.config.timePartitioningFirestoreField;
     const fieldName = this.config.timePartitioningField;
-    const fieldValue = event.data[firestoreFieldName];
+    const fieldValue =
+      event.operation === ChangeType.DELETE
+        ? event.oldData[firestoreFieldName]
+        : event.data[firestoreFieldName];
 
     if (!fieldName || !fieldValue) {
       return {};