Can Core Data avoid index rebuild when adding a new attribute during lightweight migration?

Question

Cai-Guihao OP

Created 2w

Replies 2

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I’m investigating Core Data lightweight migration behavior with SQLite and ran into a performance issue.

Scenario:

Model V1: EntityA has one fetchIndex
Model V2: EntityA adds a new optional attribute timestamp (Integer 64), with no changes to existing attributes or fetchIndex definitions

From a SQLite perspective, this change should be handled by a simple:

ALTER TABLE ZENTITYA ADD COLUMN ZTIMESTAMP INTEGER

But I observe that Core Data rebuilds the existing index, which becomes a significant performance issue for large databases.

CoreData: sql: DROP INDEX IF EXISTS Z_EntityA_id
CoreData: sql: ALTER TABLE ZENTITYA ADD COLUMN ZTIMESTAMP INTEGER
CoreData: sql: CREATE INDEX IF NOT EXISTS Z_EntityA_byID ON ZENTITYA

Question:

Is there any way to avoid or bypass index rebuilding for this kind of schema changes?

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Answer 1

DTS Engineer OP

Apple

1d

I don't see that Core Data provides any way for developers to customize the system-provided lightweight migration process, and so can only suggest that you file a feedback report – If you do so, please share your report ID here.

You might consider achieving your goal by migrating the data with your own code. That can be a bit involved though, depending on the complexity of your data set.

Best,
——
Ziqiao Chen
 Worldwide Developer Relations.

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Answer 2

Cai-Guihao OP

1d

Thank you for the clarification. I’ve submitted FB22758653.

Regarding the suggestion to migrate the data with custom code, could you elaborate more on the approach?

Do you mean:

Implementing a custom Core Data migration flow? My understanding is that fetch indexes may still be recreated because Core Data still detects the entity’s version hash change.
Directly managing the underlying SQLite schema manually? If so, how would Core Data become compatible with the updated store afterward?

I’d appreciate any additional guidance on the recommended approach here.

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