feat: Add dashboard widget snapshot model (#95236)

We'd like to store a snapshot of the last valid transaction widget
while we do an in-place migration of widgets from transactions -> spans.
This allows us to recover the original transaction state of the
widget in case something goes horribly wrong.

Author: shruthilayaj

migrations_lockfile.txt

@@ -27,7 +27,7 @@ preprod: 0010_actual_drop_preprod_artifact_analysis_file_id_col
 
 replays: 0006_add_bulk_delete_job
 
-sentry: 0948_ds_waiver_org_fk_not_db_constr
+sentry: 0949_add_dashboard_widget_snapshot_model
 
 social_auth: 0003_social_auth_json_field
 

src/sentry/migrations/0949_add_dashboard_widget_snapshot_model.py

@@ -0,0 +1,53 @@
+# Generated by Django 5.2.1 on 2025-07-15 15:03
+
+import django.db.models.deletion
+from django.db import migrations
+
+import sentry.db.models.fields.bounded
+import sentry.db.models.fields.foreignkey
+import sentry.db.models.fields.jsonfield
+from sentry.new_migrations.migrations import CheckedMigration
+
+
+class Migration(CheckedMigration):
+    # This flag is used to mark that a migration shouldn't be automatically run in production.
+    # This should only be used for operations where it's safe to run the migration after your
+    # code has deployed. So this should not be used for most operations that alter the schema
+    # of a table.
+    # Here are some things that make sense to mark as post deployment:
+    # - Large data migrations. Typically we want these to be run manually so that they can be
+    #   monitored and not block the deploy for a long period of time while they run.
+    # - Adding indexes to large tables. Since this can take a long time, we'd generally prefer to
+    #   run this outside deployments so that we don't block them. Note that while adding an index
+    #   is a schema change, it's completely safe to run the operation after the code has deployed.
+    # Once deployed, run these manually via: https://develop.sentry.dev/database-migrations/#migration-deployment
+
+    is_post_deployment = False
+
+    dependencies = [
+        ("sentry", "0948_ds_waiver_org_fk_not_db_constr"),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="DashboardWidgetSnapshot",
+            fields=[
+                (
+                    "id",
+                    sentry.db.models.fields.bounded.BoundedBigAutoField(
+                        primary_key=True, serialize=False
+                    ),
+                ),
+                ("data", sentry.db.models.fields.jsonfield.JSONField(default=dict)),
+                (
+                    "widget",
+                    sentry.db.models.fields.foreignkey.FlexibleForeignKey(
+                        on_delete=django.db.models.deletion.CASCADE, to="sentry.dashboardwidget"
+                    ),
+                ),
+            ],
+            options={
+                "abstract": False,
+            },
+        ),
+    ]

src/sentry/models/dashboard_widget.py

@@ -258,6 +258,14 @@ class Meta:
     __repr__ = sane_repr("extraction_state", "spec_hashes")
 
 
+@region_silo_model
+class DashboardWidgetSnapshot(Model):
+    __relocation_scope__ = RelocationScope.Organization
+
+    widget = FlexibleForeignKey("sentry.DashboardWidget")
+    data: models.Field[dict[str, Any], dict[str, Any]] = JSONField()
+
+
 @region_silo_model
 class DashboardWidget(Model):
     """

src/sentry/testutils/helpers/backups.py

@@ -70,6 +70,7 @@
     DashboardWidget,
     DashboardWidgetQuery,
     DashboardWidgetQueryOnDemand,
+    DashboardWidgetSnapshot,
     DashboardWidgetTypes,
 )
 from sentry.models.dynamicsampling import CustomDynamicSamplingRule
@@ -596,6 +597,10 @@ def create_exhaustive_organization(
             extraction_state=DashboardWidgetQueryOnDemand.OnDemandExtractionState.DISABLED_NOT_APPLICABLE,
             spec_hashes=[],
         )
+        DashboardWidgetSnapshot.objects.create(
+            widget=widget,
+            data={"test": "data"},
+        )
         DashboardTombstone.objects.create(organization=org, slug=f"test-tombstone-in-{slug}")
 
         # *Search