apache/cassandra · warning

Failed to refresh compression dictionary for

Error message

Failed to refresh compression dictionary for {}.{}

What it means

The periodic dictionary refresh task reads the latest compression dictionary for a table from the system_distributed keyspace and adds it to the local cache. On any exception (missing row, deserialization, I/O) it logs this warning and skips the refresh; existing compression continues without the newest dictionary until the next scheduled run.

Solutions

1. Check the logged exception and verify the latest dictionary row exists in system_distributed for the table id.
2. Repair system_distributed so dictionary data replicates, then let the next scheduled refresh retry.
3. Confirm the table was not dropped/recreated (table id change) and re-enable dictionary compression if needed.
4. If refreshes keep failing, disable/re-enable dictionary-based compression to retrain and repopulate.

// precheck that latest dictionary row is visible
Row latest = session.execute("SELECT * FROM system_distributed.compression_dictionaries WHERE keyspace_name=? AND table_name=?", ks, table).one();
boolean dictionaryAvailable = latest != null;

try { refreshFromSystemTable(); } catch (Exception e) { logger.warn("refresh skipped; will retry next cycle", e); }

When it happens

Trigger: refreshDictionaryFromSystemTable runs on schedule and SystemDistributedKeyspace.retrieveLatestCompressionDictionary throws for the keyspace/table — e.g. the dictionary row is absent or not yet replicated.

Common situations: system_distributed not fully repaired after adding nodes; dictionary publisher deleted rows; transient storage/consistency errors; table id mismatch after table recreation.

Understand the failure class

Background: 'Could not be found', 'does not exist', 'not found in database': the resource-not-found family when an ID, slug, key, or URI lookup comes back empty — this error's family across 20 libraries.

Related errors

• Failed to retrieve compression dictionary for
• Failed to send dictionary update notification to
• Provided dictionary can not be consumed by table's…
• Access forbidden
• Cannot access method create in

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/7fb6cb5876a363a8. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/db/compression/CompressionDictionaryScheduler.java:184

    /**
     * Refreshes dictionary from system table and updates the cache.
     * This method is called periodically by the scheduled refresh task.
     */
    private void refreshDictionaryFromSystemTable()
    {
        try
        {
            if (!isEnabled)
            {
                return;
            }

            CompressionDictionary dictionary = SystemDistributedKeyspace.retrieveLatestCompressionDictionary(keyspaceName, tableName, tableId);
            cache.add(dictionary);
        }
        catch (Exception e)
        {
            logger.warn("Failed to refresh compression dictionary for {}.{}",
                        keyspaceName, tableName, e);
        }
    }

    @Override
    public void close()
    {
        if (scheduledRefreshTask != null)
        {
            scheduledRefreshTask.cancel(false);
            scheduledRefreshTask = null;
        }

        finishTraining(TrainingState.notStarted());
    }

    /**
     * Task that samples chunks from existing SSTables and triggers training.

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