influxdata/influxdb · error · Error

error in last cache

Error message

error in last cache: {0}

What it means

This transparent wrapper converts a `last_cache::Error` — a failure in the last-N-values cache attached to a table. The last cache stores the most recent values per tag combination for fast lookup; errors here mean cache creation, update, or lookup failed, independent of the core write.

Solutions

1. Read the inner last_cache::Error for the exact cause
2. Verify cache key/value columns still exist in the table schema with the expected types
3. Recreate the last cache with valid size/TTL and existing column names

Example fix

// before
create_last_cache(db, table, "c", Some(vec!["old_col"]), None, None)?; // column gone
// after
let cols = valid_key_columns(db, table)?; // check schema first
create_last_cache(db, table, "c", Some(cols), None, None)?;

// validate last-cache config before creation
let schema = catalog.table(db, table)?.schema();
for key in &key_columns {
    assert!(schema.field(key).is_some(), "cache key column {key} not in schema");
}
assert!(cache_size.is_none() || cache_size.unwrap() > 0, "cache size must be > 0");

fn is_last_cache_error(e: &WriteBufferError) -> Option<&last_cache::Error> {
    match e { WriteBufferError::LastCacheError(e) => Some(e), _ => None }
}

When it happens

Trigger: Creating a last cache with invalid configuration (bad TTL/count, nonexistent columns used as key/value columns), or updating/looking up a cache during writes when the cache state is inconsistent with the table schema.

Common situations: Configuring a cache on a column that was later dropped or type-changed; cache size/TTL values out of accepted bounds; referencing renamed columns in cached definitions after a schema change.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

• last cache already exists for database and table, but it…
• cache not found
• catalog update error
• column id in series key should be valid
• database name error

AI-assisted analysis of influxdata/influxdb@06200ef96b (2026-09-19). Data as JSON: /api/errors/9db4d5782a3ff33f. Report an issue: GitHub.

Appendix: source

Thrown at influxdb3_write/src/write_buffer/mod.rs:98

        new: ColumnType,
    },

    #[error("catalog update error: {0}")]
    CatalogUpdateError(#[from] CatalogError),

    #[error("error from persister: {0}")]
    PersisterError(#[from] PersisterError),

    #[error("corrupt load state: {0}")]
    CorruptLoadState(String),

    #[error("database name error: {0}")]
    DatabaseNameError(#[from] DatabaseNameError),

    #[error("error from table buffer: {0}")]
    TableBufferError(#[from] table_buffer::Error),

    #[error("error in last cache: {0}")]
    LastCacheError(#[from] last_cache::Error),

    #[error("database not found {db_name:?}")]
    DatabaseNotFound { db_name: String },

    #[error("table not found {table_name:?} in db {db_name:?}")]
    TableNotFound { db_name: String, table_name: String },

    #[error("tried accessing database that does not exist")]
    DbDoesNotExist,

    #[error("tried creating database named '{0}' that already exists")]
    DatabaseExists(String),

    #[error("cannot write to soft-deleted database '{0}' - it is marked for deletion")]
    DatabaseDeleted(String),

    #[error("tried accessing table that do not exist")]

View on GitHub (pinned to 06200ef96b)