clockworklabs/SpacetimeDB · error · anyhow::Error

Precheck failed: added sequence {sequence_name} already has

Error message

Precheck failed: added sequence {sequence_name} already has values in range

What it means

During auto-migration, when a plan step adds a sequence (auto_inc) to an existing table, a precheck iterates rows whose value in that column falls within the sequence's [min..=max] range. If any existing row already holds a value the sequence would generate, migration aborts to prevent future primary-key/ID collisions.

Source

Thrown at crates/engine/src/update.rs:257

                    .ok_or_else(|| {
                        anyhow::anyhow!("Precheck failed: added sequence {sequence_name} has invalid min value")
                    })?;

                let max = match sequence_def.max_value {
                    Some(max) => ty.saturating_value_from_i128(max),
                    None => ty.saturating_value_from_i128(i128::MAX),
                }
                .ok_or_else(|| {
                    anyhow::anyhow!("Precheck failed: added sequence {sequence_name} has invalid max value")
                })?;

                let range = min..=max;
                if stdb
                    .iter_by_col_range_mut(tx, table_id, sequence_def.column, range)?
                    .next()
                    .is_some()
                {
                    anyhow::bail!("Precheck failed: added sequence {sequence_name} already has values in range",);
                }
            }
        }
    }

    log::info!("Running database update steps: {}", stdb.database_identity());
    let mut res = UpdateResult::Success;

    for step in plan.steps {
        match step {
            spacetimedb_schema::auto_migrate::AutoMigrateStep::RemoveTable(table_name_key) => {
                let (namespace, local) = table_name_key;
                let table_name = joined(namespace, local);
                let table_id = stdb.table_id_from_name_mut(tx, &table_name)?.unwrap();

                if stdb.table_row_count_mut(tx, table_id).unwrap_or(0) > 0 {
                    anyhow::bail!(
                        "Cannot remove table `{table_name}`: table contains data. \

View on GitHub (pinned to 6dee26c6ef)

Solutions

1. Check the current maximum (SELECT MAX(col) FROM t) and define the sequence to start strictly above it
2. Or delete/backfill the conflicting rows so none fall inside the sequence range, then re-run the migration
3. If the ids are disposable, clear the table before adding the sequence
4. Prefer an explicit, reviewed migration over auto-migrate when the table already holds production data

Example fix

-- before: rows with id 1..50 exist, sequence starts at 1 -> precheck fails
ALTER TABLE my_table ... auto_inc on id;

-- after: start beyond the current max, or clear the data first
SELECT MAX(id) FROM my_table;  -- 50
CREATE SEQUENCE my_seq START 51;
-- or: DELETE FROM my_table; then re-run the migration

-- before adding a sequence to an existing column
spacetime sql my-db 'SELECT MAX(id) FROM my_table';
-- the new sequence must start strictly above this value

When it happens

Trigger: Adding #[auto_inc]/a sequence to a column of a table that already contains rows with values inside the new sequence's range -- e.g. ids 1..50 exist and the sequence starts at 1; or seeded/imported data written with explicit ids before the sequence is introduced.

Common situations: Retrofitting auto_inc onto a manually populated table; importing seed data then adding the sequence in the same release; a migration that re-adds a sequence after data was written by explicit-id inserts.

Related errors

• Cannot remove table `{table_name}`: table contains data. Cle
• TableId `{return_id}` does not exist
• table {} not found in old_module_def
• table should exist in the database for AddConstraint
• Index '${indexLabel}' on table '${tableLabel}' must define a

AI-assisted analysis of clockworklabs/SpacetimeDB@6dee26c6ef (2026-08-20). Data as JSON: /api/errors/2e23f0b24865357e. Report an issue: GitHub.