Experimental change to the handling of foreign key constraint violations when applyin...

Experimental change to the handling of foreign key constraint violations when applying a changeset: all foreign keys, immediate and deferred, are deferred until the end of the transaction (or sub-transaction) opened by the sqlite3changeset_apply(). A single call to the conflict-handler (if any) is made if any FK constraint violations are still present in the database at this point. The conflict-handler may choose to rollback the changeset, or to apply it, constraint violations and all.

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