ScyllaDB University LIVE, FREE Virtual Training Event | March 21
Register for Free
ScyllaDB Documentation Logo Documentation
  • Server
  • Cloud
  • Tools
    • ScyllaDB Manager
    • ScyllaDB Monitoring Stack
    • ScyllaDB Operator
  • Drivers
    • CQL Drivers
    • DynamoDB Drivers
  • Resources
    • ScyllaDB University
    • Community Forum
    • Tutorials
Download
ScyllaDB Docs ScyllaDB Enterprise Troubleshooting ScyllaDB Data Modeling ScyllaDB Large Partitions Table

Caution

You're viewing documentation for a previous version. Switch to the latest stable version.

ScyllaDB Large Partitions Table¶

This document describes how to work with ScyllaDB’s large partitions table. The large partitions table can be used to trace large partitions in a cluster. The table is updated every time a partition is written and/or deleted,and includes a compaction process which flushes MemTables to SSTables.

Large Partitions can cause any of the following symptoms:

  • Longer latencies on a single shard (look at the “ScyllaDB Overview Metrics” dashboard of ScyllaDB Monitoring Stack).

  • Oversized allocation warning messages in the log (e.g. seastar_memory - oversized allocation: 2842624 bytes, please report)

If you are experiencing any of the above, search to see if you have large partitions.

Note that large partitions are detected only when they are stored in a single SSTable. ScyllaDB does not account for data belonging to the same logical partition, but spread across multiple SSTables, as long as any single partition in each SSTable does not cross the large partitions warning threshold. However, note that over time, compaction, and Size-Tiered Compaction Strategy in particular, may collect the dispersed partition data from several SSTables and store it in a single SSTable, thus crossing the large partitions threshold.

Viewing - Find Large Partitions¶

  • Search for large partitions.

For example:

SELECT * FROM system.large_partitions;

Example output:

keyspace_name | table_name | sstable_name     | partition_size | partition_key                                       | compaction_time     | dead_rows | range_tombstones | rows
--------------+------------+------------------+----------------+-----------------------------------------------------+---------------------+-----------+------------------+--------
       demodb |       tmcr | md-6-big-Data.db |     1188716932 | {key: pk{000400000001}, token:-4069959284402364209} | 2018-07-23 08:10:34 |         0 |                0 |    100
       testdb |       tmcr | md-7-big-Data.db |        1234567 | {key: pk{000400000001}, token:-3169959284402457813} | 2018-07-23 08:10:34 |         0 |                0 | 100101

Parameter

Description

keyspace_name

The name of a keyspace holding the large partition

table_name

The name of a table containing the large partition

sstable_name

The name of SSTable containing the large partition

partition_size

The size of the partition in this sstable

partition_key

The value of a partition key that identifies the large partition

dead_rows

The number of dead rows in the partition in this sstable

range_tombstones

The number of range tombstones in the partition in this sstable

rows

The number of rows including range tombstones in the partition in this sstable

compaction_time

Time when compaction last occurred

Note

The large partitions table is local per node. Querying the table returns results for the specific node you query.

  • Search within all the large partitions for a specific keyspace and or table.

For example we are looking for the keyspace demodb and table tmcr:

SELECT * FROM system.large_partitions WHERE keyspace_name = 'demodb' AND table_name = 'tmcr';

Example output:

keyspace_name | table_name | sstable_name     | partition_size | partition_key                                       | compaction_time     | dead_rows | range_tombstones | rows
--------------+------------+------------------+----------------+-----------------------------------------------------+---------------------+-----------+------------------+------
       demodb |       tmcr | md-6-big-Data.db |     1188716932 | {key: pk{000400000001}, token:-4069959284402364209} | 2018-07-23 08:10:34 |         0 |                0 | 1942

Configure¶

Configure the detection thresholds of large partitions with the compaction_large_partition_warning_threshold_mb parameter (default: 1000MB) and the compaction_rows_count_warning_threshold parameter (default 100000) in the scylla.yaml configuration file. Partitions that are bigger than the size threshold and/or hold more than the rows count threshold are reported in the system.large_partitions table and generate a warning in the ScyllaDB log (refer to log).

For example (set to 500MB / 50000, respectively):

compaction_large_partition_warning_threshold_mb: 500
compaction_rows_count_warning_threshold: 50000

Storing¶

Large partitions are stored in a system table with the following schema:

DESCRIBE TABLE system.large_partitions;

CREATE TABLE system.large_partitions (
    keyspace_name text,
    table_name text,
    sstable_name text,
    partition_size bigint,
    partition_key text,
    compaction_time timestamp,
    dead_rows bigint,
    range_tombstones bigint,
    rows bigint,
    PRIMARY KEY ((keyspace_name, table_name), sstable_name, partition_size, partition_key)
) WITH CLUSTERING ORDER BY (sstable_name ASC, partition_size DESC, partition_key ASC)

Expiring Data¶

In order to prevent stale data from appearing, all rows in system.large_partitions table are inserted with Time To Live (TTL) equal to 30 days.

Troubleshoot

Additional Resources¶

Large Partitions Hunting

Was this page helpful?

PREVIOUS
Data Modeling
NEXT
ScyllaDB Large Rows and Large Cells Tables
  • Create an issue

On this page

  • ScyllaDB Large Partitions Table
    • Viewing - Find Large Partitions
    • Configure
    • Storing
    • Expiring Data
    • Additional Resources
ScyllaDB Enterprise
  • enterprise
    • 2024.2
    • 2024.1
    • 2023.1
    • 2022.2
  • Getting Started
    • Install ScyllaDB Enterprise
      • ScyllaDB Web Installer for Linux
      • Install ScyllaDB Without root Privileges
      • Install scylla-jmx Package
      • Air-gapped Server Installation
      • ScyllaDB Housekeeping and how to disable it
      • ScyllaDB Developer Mode
      • Launch ScyllaDB on AWS
      • Launch ScyllaDB on GCP
      • Launch ScyllaDB on Azure
    • Configure ScyllaDB
    • ScyllaDB Configuration Reference
    • ScyllaDB Requirements
      • System Requirements
      • OS Support
      • Cloud Instance Recommendations
      • ScyllaDB in a Shared Environment
    • Migrate to ScyllaDB
      • Migration Process from Cassandra to ScyllaDB
      • ScyllaDB and Apache Cassandra Compatibility
      • Migration Tools Overview
    • Integration Solutions
      • Integrate ScyllaDB with Spark
      • Integrate ScyllaDB with KairosDB
      • Integrate ScyllaDB with Presto
      • Integrate ScyllaDB with Elasticsearch
      • Integrate ScyllaDB with Kubernetes
      • Integrate ScyllaDB with the JanusGraph Graph Data System
      • Integrate ScyllaDB with DataDog
      • Integrate ScyllaDB with Kafka
      • Integrate ScyllaDB with IOTA Chronicle
      • Integrate ScyllaDB with Spring
      • Shard-Aware Kafka Connector for ScyllaDB
      • Install ScyllaDB with Ansible
      • Integrate ScyllaDB with Databricks
      • Integrate ScyllaDB with Jaeger Server
      • Integrate ScyllaDB with MindsDB
    • Tutorials
  • ScyllaDB for Administrators
    • Administration Guide
    • Procedures
      • Cluster Management
      • Backup & Restore
      • Change Configuration
      • Maintenance
      • Best Practices
      • Benchmarking ScyllaDB
      • Migrate from Cassandra to ScyllaDB
      • Disable Housekeeping
    • Security
      • ScyllaDB Security Checklist
      • Enable Authentication
      • Enable and Disable Authentication Without Downtime
      • Creating a Custom Superuser
      • Generate a cqlshrc File
      • Reset Authenticator Password
      • Enable Authorization
      • Grant Authorization CQL Reference
      • Certificate-based Authentication
      • Role Based Access Control (RBAC)
      • ScyllaDB Auditing Guide
      • Encryption: Data in Transit Client to Node
      • Encryption: Data in Transit Node to Node
      • Generating a self-signed Certificate Chain Using openssl
      • Configure SaslauthdAuthenticator
      • Encryption at Rest
      • LDAP Authentication
      • LDAP Authorization (Role Management)
      • Software Bill Of Materials (SBOM)
    • Admin Tools
      • Nodetool Reference
      • CQLSh
      • Admin REST API
      • Tracing
      • ScyllaDB SStable
      • ScyllaDB Types
      • SSTableLoader
      • cassandra-stress
      • SSTabledump
      • SSTableMetadata
      • ScyllaDB Logs
      • Seastar Perftune
      • Virtual Tables
      • Reading mutation fragments
      • Maintenance socket
      • Maintenance mode
      • Task manager
    • Version Support Policy
    • ScyllaDB Monitoring Stack
    • ScyllaDB Operator
    • ScyllaDB Manager
    • Upgrade Procedures
      • About Upgrade
      • Upgrade Guides
    • System Configuration
      • System Configuration Guide
      • scylla.yaml
      • ScyllaDB Snitches
    • Benchmarking ScyllaDB
    • ScyllaDB Diagnostic Tools
  • ScyllaDB for Developers
    • Develop with ScyllaDB
    • Tutorials and Example Projects
    • Learn to Use ScyllaDB
    • ScyllaDB Alternator
    • ScyllaDB Drivers
      • ScyllaDB CQL Drivers
      • ScyllaDB DynamoDB Drivers
  • CQL Reference
    • CQLSh: the CQL shell
    • Appendices
    • Compaction
    • Consistency Levels
    • Consistency Level Calculator
    • Data Definition
    • Data Manipulation
      • SELECT
      • INSERT
      • UPDATE
      • DELETE
      • BATCH
    • Data Types
    • Definitions
    • Global Secondary Indexes
    • Expiring Data with Time to Live (TTL)
    • Functions
    • Wasm support for user-defined functions
    • JSON Support
    • Materialized Views
    • Non-Reserved CQL Keywords
    • Reserved CQL Keywords
    • DESCRIBE SCHEMA
    • Service Levels
    • ScyllaDB CQL Extensions
  • Features
    • Lightweight Transactions
    • Global Secondary Indexes
    • Local Secondary Indexes
    • Materialized Views
    • Counters
    • Change Data Capture
      • CDC Overview
      • The CDC Log Table
      • Basic operations in CDC
      • CDC Streams
      • CDC Stream Generations
      • Querying CDC Streams
      • Advanced column types
      • Preimages and postimages
      • Data Consistency in CDC
    • Workload Attributes
    • Workload Prioritization
  • ScyllaDB Architecture
    • Data Distribution with Tablets
    • ScyllaDB Ring Architecture
    • ScyllaDB Fault Tolerance
    • Consistency Level Console Demo
    • ScyllaDB Anti-Entropy
      • ScyllaDB Hinted Handoff
      • ScyllaDB Read Repair
      • ScyllaDB Repair
    • SSTable
      • ScyllaDB SSTable - 2.x
      • ScyllaDB SSTable - 3.x
    • Compaction Strategies
    • Raft Consensus Algorithm in ScyllaDB
    • Zero-token Nodes
  • Troubleshooting ScyllaDB
    • Errors and Support
      • Report a ScyllaDB problem
      • Error Messages
      • Change Log Level
    • ScyllaDB Startup
      • Ownership Problems
      • ScyllaDB will not Start
      • ScyllaDB Python Script broken
    • Upgrade
      • Inaccessible configuration files after ScyllaDB upgrade
    • Cluster and Node
      • Handling Node Failures
      • Failure to Add, Remove, or Replace a Node
      • Failed Decommission Problem
      • Cluster Timeouts
      • Node Joined With No Data
      • NullPointerException
      • Failed Schema Sync
    • Data Modeling
      • ScyllaDB Large Partitions Table
      • ScyllaDB Large Rows and Cells Table
      • Large Partitions Hunting
      • Failure to Update the Schema
    • Data Storage and SSTables
      • Space Utilization Increasing
      • Disk Space is not Reclaimed
      • SSTable Corruption Problem
      • Pointless Compactions
      • Limiting Compaction
    • CQL
      • Time Range Query Fails
      • COPY FROM Fails
      • CQL Connection Table
    • ScyllaDB Monitor and Manager
      • Manager and Monitoring integration
      • Manager lists healthy nodes as down
    • Installation and Removal
      • Removing ScyllaDB on Ubuntu breaks system packages
  • Knowledge Base
    • Upgrading from experimental CDC
    • Compaction
    • Consistency in ScyllaDB
    • Counting all rows in a table is slow
    • CQL Query Does Not Display Entire Result Set
    • When CQLSh query returns partial results with followed by “More”
    • Run ScyllaDB and supporting services as a custom user:group
    • Customizing CPUSET
    • Decoding Stack Traces
    • Snapshots and Disk Utilization
    • DPDK mode
    • Debug your database with Flame Graphs
    • Efficient Tombstone Garbage Collection in ICS
    • How to Change gc_grace_seconds for a Table
    • Gossip in ScyllaDB
    • Increase Permission Cache to Avoid Non-paged Queries
    • How does ScyllaDB LWT Differ from Apache Cassandra ?
    • Map CPUs to ScyllaDB Shards
    • ScyllaDB Memory Usage
    • NTP Configuration for ScyllaDB
    • Updating the Mode in perftune.yaml After a ScyllaDB Upgrade
    • POSIX networking for ScyllaDB
    • ScyllaDB consistency quiz for administrators
    • Recreate RAID devices
    • How to Safely Increase the Replication Factor
    • ScyllaDB and Spark integration
    • Increase ScyllaDB resource limits over systemd
    • ScyllaDB Seed Nodes
    • How to Set up a Swap Space
    • ScyllaDB Snapshots
    • ScyllaDB payload sent duplicated static columns
    • Stopping a local repair
    • System Limits
    • How to flush old tombstones from a table
    • Time to Live (TTL) and Compaction
    • ScyllaDB Nodes are Unresponsive
    • Update a Primary Key
    • Using the perf utility with ScyllaDB
    • Configure ScyllaDB Networking with Multiple NIC/IP Combinations
  • Reference
    • AWS Images
    • Azure Images
    • GCP Images
    • Configuration Parameters
    • Glossary
    • Limits
    • ScyllaDB Enterprise vs. Open Source Matrix
    • API Reference (BETA)
    • Metrics (BETA)
  • ScyllaDB University
  • ScyllaDB FAQ
  • Alternator: DynamoDB API in Scylla
    • Getting Started With ScyllaDB Alternator
    • ScyllaDB Alternator for DynamoDB users
    • Alternator-specific APIs
Docs Tutorials University Contact Us About Us
© 2025, ScyllaDB. All rights reserved. | Terms of Service | Privacy Policy | ScyllaDB, and ScyllaDB Cloud, are registered trademarks of ScyllaDB, Inc.
Last updated on 09 Apr 2025.
Powered by Sphinx 7.4.7 & ScyllaDB Theme 1.8.6