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For SQLite’s documented table-rebuild procedure, turn foreign-key enforcement off on the migration connection before starting a transaction, rebuild the table and its dependent objects, run PRAGMA foreign_key_check, then commit and restore the prior enforcement setting. Changing PRAGMA foreign_keys inside a transaction or savepoint is a no-op. The exact schema statements depend on your database; the sequence below is the safe starting point.
Why a table rebuild can trigger foreign-key errors
SQLite supports only a limited set of direct ALTER TABLE changes. For other schema changes, its documented approach is to create a replacement table, copy the data, remove the old table, rename the replacement, and restore related schema objects. Dropping the old table while foreign keys are enabled can cause errors because SQLite performs an implicit delete of that table’s rows. Foreign-key actions may run, and constraints can fail immediately or report a deferred violation at commit.
SQLite’s ALTER TABLE guidance says: “If foreign key constraints are enabled, disable them using PRAGMA foreign_keys=OFF.” The setting must be changed before the rebuild transaction begins.
Use the documented rebuild sequence
Adapt the table name, columns, constraints, and data mapping to your schema. This outline is not a drop-in migration: inspect and preserve the existing indexes, triggers, and affected views before changing the table.
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- On the same connection that will run the migration, inspect and disable enforcement before opening a transaction. Query
PRAGMA foreign_keys;, issuePRAGMA foreign_keys = OFF;, then query it again to confirm the state. - Save dependent schema definitions. For example, inspect objects attached to table
XwithSELECT type, sql FROM sqlite_schema WHERE tbl_name = 'X';. Also identify views affected by the schema change; SQLite’s guidance says to drop and recreate views when necessary. - Begin a transaction and create the replacement table. Define its intended columns and constraints in
CREATE TABLE new_X (...). - Copy the data with explicit column lists. For example:
INSERT INTO new_X (column_a, column_b) SELECT column_a, column_b FROM X;. Confirm that the selected source columns and destination columns map correctly. - Drop the old table and rename the replacement. Use
DROP TABLE X;, followed byALTER TABLE new_X RENAME TO X;. - Recreate saved indexes and triggers, and restore affected views. Confirm that their definitions still refer to the intended table and columns.
- Check relationships before accepting the migration. Run
PRAGMA foreign_key_check;. It returns a row for each violation. Investigate and resolve any returned rows rather than treating a successful rename as proof of integrity. - Commit only after validation, then restore the original enforcement state. If enforcement was enabled before the migration, issue
PRAGMA foreign_keys = ON;after commit and query the pragma to verify it.
SQLite’s schema-change instructions emphasize saving and recreating associated schema objects. Its PRAGMA reference documents the validation and inspection commands used here.
Diagnose the error you see
PRAGMA foreign_keys = OFF appears to do nothing
Check whether the connection already has a transaction or savepoint open. SQLite documents that changing foreign_keys in that state has no effect. Issue the pragma before BEGIN, on the connection running the migration, and query it to inspect the result. Foreign-key enforcement is a per-connection setting, so do not assume another connection’s setting applies to this one. See SQLite’s foreign-key documentation and PRAGMA reference.
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DROP TABLE fails
With foreign keys enabled, dropping a table performs an implicit delete of its rows. That delete can invoke foreign-key actions or violate constraints. An immediate violation can make the drop fail; a deferred violation can surface at commit if it remains unresolved. Use the documented rebuild sequence, including disabling enforcement before the transaction and checking relationships before commit. See SQLite Foreign Key Support.
foreign key mismatch or no such table
These errors can point to a malformed relationship rather than a faulty copy. Verify that the referenced parent table and columns exist, and that the parent columns are a primary key or a suitable unique key. Run PRAGMA foreign_key_list(child_table); to inspect the child’s declaration, then compare it with the parent table definition and indexes. SQLite describes these configuration errors in Foreign Key Support; the command is documented in the PRAGMA reference.
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PRAGMA foreign_key_check returns rows
Each returned row identifies a violation: the child table, the offending rowid (or NULL for a WITHOUT ROWID child), the referenced parent table, and the foreign-key constraint index. Inspect the affected child data, key declarations, and data mapping. Do not accept the migration with unresolved violations; repair the problem or roll back as appropriate. See the PRAGMA reference and SQLite’s rebuild guidance.
Check rename behavior against your SQLite version
SQLite 3.26.0, released on 2018-12-01, changed how references to a renamed parent table are updated: from that version onward, they are updated even when PRAGMA foreign_keys is off, unless PRAGMA legacy_alter_table=ON. Before 3.26.0, that reference update depended on foreign-key enforcement being on. If the failure involves a rename, check the runtime SQLite version and legacy setting. The version history is in the ALTER TABLE documentation.
Why deferring constraints is not the same fix
PRAGMA defer_foreign_keys=ON delays checking all foreign-key constraints until the outermost transaction commits, regardless of how the constraints were declared. SQLite resets this setting on each commit or rollback, so it must be enabled separately for each transaction. Deferral changes when violations are checked; it does not repair invalid references or replace the rebuild procedure and its post-reconstruction check. See the PRAGMA reference.
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