> ## Documentation Index > Fetch the complete documentation index at: https://private-7c7dfe99-fix-nav-issues.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. > Overview of what system tables are and why they are useful. # System Tables {/*AUTOGENERATED_START*/} | Page | Description | | --------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | [system.constraints](/reference/system-tables/constraints) | System table containing information about existing constraints in all tables. | | [System Tables Overview](/reference/system-tables/overview) | Overview of what system tables are and why they are useful. | | [INFORMATION\_SCHEMA](/reference/system-tables/information_schema) | System database providing an almost standardized DBMS-agnostic view on metadata of database objects. | | [system.aggregate\_function\_combinators](/reference/system-tables/aggregate_function_combinators) | Contains a list of all available aggregate function combinators, which could be applied to aggregate functions and change the way they work. | | [system.aggregated\_zookeeper\_log](/reference/system-tables/aggregated_zookeeper_log) | System table containing aggregated statistics of ZooKeeper operations grouped by session, path, operation type, component, and subrequest flag. | | [system.asynchronous\_insert\_log](/reference/system-tables/asynchronous_insert_log) | System table containing information about async inserts. Each entry represents an insert query buffered into an async insert query. | | [system.asynchronous\_loader](/reference/system-tables/asynchronous_loader) | System table containing information about and status of recent asynchronous jobs (e.g. for tables which are loading). The table contains a row for every job. | | [system.asynchronous\_metric\_log](/reference/system-tables/asynchronous_metric_log) | System table containing historical values for `system.asynchronous_metrics`, which are saved once per time interval (one second by default) | | [system.asynchronous\_inserts](/reference/system-tables/asynchronous_inserts) | System table containing information about pending asynchronous inserts in queue. | | [system.asynchronous\_metrics](/reference/system-tables/asynchronous_metrics) | System table containing metrics that are calculated periodically in the background. For example, the amount of RAM in use. | | [system.azure\_queue\_settings](/reference/system-tables/azure_queue_settings) | System table containing information about settings of AzureQueue tables. Available from server version `24.10`. | | [system.azure\_queue\_metadata\_cache](/reference/system-tables/azure_queue_metadata_cache) | Contains in-memory state of AzureQueue metadata and currently processed rows per file. | | [system.azure\_queue\_log](/reference/system-tables/azure_queue_log) | Contains log entries with information about files processed by the AzureQueue engine. | | It is safe to truncate or drop this table at any time. | | | [system.background\_schedule\_pool\_log](/reference/system-tables/background_schedule_pool_log) | System table containing history of background schedule pool task executions. | | [system.background\_schedule\_pool](/reference/system-tables/background_schedule_pool) | System table containing information about tasks in background schedule pools. | | [system.backup\_log](/reference/system-tables/backup_log) | System table containing logging entries with information about `BACKUP` and `RESTORE` operations. | | [system.backups](/reference/system-tables/backups) | System table containing logging entries with information about `BACKUP` and `RESTORE` operations. | | [system.blob\_storage\_log](/reference/system-tables/blob_storage_log) | System table containing logging entries with information about various blob storage operations such as uploads and deletes. | | [system.build\_options](/reference/system-tables/build_options) | System table containing information about ClickHouse server's build options. | | [system.certificates](/reference/system-tables/certificates) | Contains information about available certificates and their sources. | | [system.clusters](/reference/system-tables/clusters) | System table containing information about clusters available in the config file and the servers defined in them. | | [system.codecs](/reference/system-tables/codecs) | System table containing information about codecs in queue. | | [system.collations](/reference/system-tables/collations) | Contains a list of all available collations for alphabetical comparison of strings. | | [system.columns](/reference/system-tables/columns) | System table containing information about columns in all tables | | [system.completions](/reference/system-tables/completions) | Contains a list of completion tokens. | | [system.contributors](/reference/system-tables/contributors) | System table containing information about contributors. | | [system.crash\_log](/reference/system-tables/crash_log) | System table containing information about stack traces for fatal errors. | | [system.current\_roles](/reference/system-tables/current_roles) | System table containing active roles for the current user. | | [system.dashboards](/reference/system-tables/dashboards) | Contains queries used by `/dashboard` page accessible though the HTTP interface. useful for monitoring and troubleshooting. | | [system.data\_skipping\_indices](/reference/system-tables/data_skipping_indices) | System table containing information about existing data skipping indices in all the tables. | | [system.data\_skipping\_index\_types](/reference/system-tables/data_skipping_index_types) | System table containing a list of data skipping index types supported by the server along with their embedded documentation. | | [system.data\_type\_families](/reference/system-tables/data_type_families) | System table containing information about supported data types | | [system.database\_engines](/reference/system-tables/database_engines) | System table containing a list of database engines supported by the server. | | [system.database\_replicas](/reference/system-tables/database_replicas) | System table containing information about and status of replicated database. | | [system.databases](/reference/system-tables/databases) | System table containing information about the databases that are available to the current user. | | [system.dead\_letter\_queue](/reference/system-tables/dead_letter_queue) | System table containing information about messages received via a streaming engine and parsed with errors. | | [system.delta\_lake\_metadata\_log](/reference/system-tables/delta_metadata_log) | System table containing information about metadata files read from Delta Lake tables. Each entry represents a root metadata JSON file. | | [system.detached\_parts](/reference/system-tables/detached_parts) | System table containing information about detached parts of MergeTree tables | | [system.detached\_tables](/reference/system-tables/detached_tables) | System table containing information about each detached table. | | [system.dictionaries](/reference/system-tables/dictionaries) | System table containing information about dictionaries | | [system.dictionary\_sources](/reference/system-tables/dictionary_sources) | System table containing a list of dictionary sources supported by the server along with their embedded documentation. | | [system.dictionary\_layouts](/reference/system-tables/dictionary_layouts) | System table containing a list of dictionary layouts supported by the server along with their embedded documentation. | | [system.dimensional\_metrics](/reference/system-tables/dimensional_metrics) | This table contains dimensional metrics that can be calculated instantly and exported in the Prometheus format. It is always up to date. | | [system.disk\_types](/reference/system-tables/disk_types) | System table containing a list of disk types supported by the server along with their embedded documentation. | | [system.disks](/reference/system-tables/disks) | System table containing information about disks defined in the server configuration | | [system.distributed\_ddl\_queue](/reference/system-tables/distributed_ddl_queue) | System table containing information about distributed ddl queries (queries using the ON CLUSTER clause) that were executed on a cluster. | | [system.distribution\_queue](/reference/system-tables/distribution_queue) | System table containing information about local files that are in the queue to be sent to the shards. | | [system.dns\_cache](/reference/system-tables/dns_cache) | System table containing information about cached DNS records. | | [system.documentation](/reference/system-tables/documentation) | System table that collects the embedded documentation of the uniform components of the system (functions, table engines, data types, and so on) into a single table, with the reference documentation rendered as Markdown. | | [system.dropped\_tables](/reference/system-tables/dropped_tables) | System table containing information about tables that drop table has been executed on but for which data cleanup has not yet been performed | | [system.dropped\_tables\_parts](/reference/system-tables/dropped_tables_parts) | System table containing information about parts of MergeTree dropped tables from `system.dropped_tables` | | [system.enabled\_roles](/reference/system-tables/enabled_roles) | System table containing all active roles at the moment, including the current role of the current user and the granted roles for the current role | | [system.error\_log](/reference/system-tables/error_log) | System table containing the history of error values from table `system.errors`, periodically flushed to disk. | | [system.errors](/reference/system-tables/errors) | System table containing error codes with the number of times they have been triggered. | | [system.events](/reference/system-tables/events) | System table containing information about the number of events that have occurred in the system. | | [system.fail\_points](/reference/system-tables/fail_points) | Contains a list of all available failpoints with their type and current status. | | [system.filesystem\_cache\_settings](/reference/system-tables/filesystem_cache_settings) | Contains information about all filesystem cache settings | | [system.filesystem\_read\_prefetches\_log](/reference/system-tables/filesystem_read_prefetches_log) | Contains a history of all prefetches done during reading from MergeTree tables backed by a remote filesystem. | | It is safe to truncate or drop this table at any time. | | | [system.filesystem\_cache\_log](/reference/system-tables/filesystem_cache_log) | Contains a history of all events occurred with filesystem cache for objects on a remote filesystem. | | It is safe to truncate or drop this table at any time. | | | [system.filesystem\_cache](/reference/system-tables/filesystem_cache) | Contains information about all entries inside filesystem cache for remote objects. | | [system.formats](/reference/system-tables/formats) | Contains a list of all the formats along with flags whether a format is suitable for input/output or whether it supports parallelization. | | [system.functions](/reference/system-tables/functions) | System table containing information about normal and aggregate functions. | | [system.grants](/reference/system-tables/grants) | System table showing which privileges are granted to ClickHouse user accounts. | | [system.graphite\_retentions](/reference/system-tables/graphite_retentions) | System table containing information about parameters `graphite_rollup` which are used in tables with `GraphiteMergeTree` type engines. | | [system.histogram\_metrics](/reference/system-tables/histogram_metrics) | This table contains histogram metrics that can be calculated instantly and exported in the Prometheus format. It is always up to date. | | [system.iceberg\_history](/reference/system-tables/iceberg_history) | System iceberg snapshot history | | [system.iceberg\_files](/reference/system-tables/iceberg_files) | System table containing per-file metadata of Iceberg tables | | [system.iceberg\_metadata\_log](/reference/system-tables/iceberg_metadata_log) | System table containing information about metadata files read from Iceberg tables. Each entry represents either a root metadata file, metadata extracted from an Avro file, or an entry of some Avro file. | | [system.instrumentation](/reference/system-tables/instrumentation) | System table containing the instrumentation points | | [system.jemalloc\_stats](/reference/system-tables/jemalloc_stats) | Returns jemalloc statistics in a single row with a single column. Equivalent to SYSTEM JEMALLOC STATS command. | | [system.jemalloc\_bins](/reference/system-tables/jemalloc_bins) | System table containing information about memory allocations done via jemalloc allocator in different size classes (bins) aggregated from all arenas. | | [system.jemalloc\_profile\_text](/reference/system-tables/jemalloc_profile_text) | Displays the symbolized jemalloc heap profile. Run 'SYSTEM JEMALLOC FLUSH PROFILE' to generate a profile first. | | [system.kafka\_consumers](/reference/system-tables/kafka_consumers) | System table containing information about Kafka consumers. | | [system.keeper\_cluster](/reference/system-tables/keeper_cluster) | System table which exists only when this node runs an in-process ClickHouse Keeper. Contains one row per Raft cluster member as seen by this Keeper. | | [system.keeper\_snapshots](/reference/system-tables/keeper_snapshots) | System table which exists only when this node runs an in-process ClickHouse Keeper. Contains one row per on-disk Raft snapshot tracked by the Keeper state machine. | | [system.keeper\_changelogs](/reference/system-tables/keeper_changelogs) | System table which exists only when this node runs an in-process ClickHouse Keeper. Contains one row per on-disk Raft changelog file tracked by the Keeper log store. | | [system.keywords](/reference/system-tables/keywords) | Contains a list of all keywords used in ClickHouse parser. | | [system.licenses](/reference/system-tables/licenses) | System table containing licenses of third-party libraries that are located in the contrib directory of ClickHouse sources. | | [system.macros](/reference/system-tables/macros) | Contains a list of all macros defined in server configuration. | | [system.masking\_policies](/reference/system-tables/masking_policies) | System table containing information about all masking policies in the system. | | [system.merge\_tree\_settings](/reference/system-tables/merge_tree_settings) | System table containing information about settings for MergeTree tables. | | [system.merges](/reference/system-tables/merges) | System table containing information about merges and part mutations currently in process for tables in the MergeTree family. | | [system.metric\_log](/reference/system-tables/metric_log) | System table containing history of metrics values from tables `system.metrics` and `system.events`, periodically flushed to disk. | | [system.metrics](/reference/system-tables/metrics) | System table containing metrics which can be calculated instantly, or have a current value. | | [system.models](/reference/system-tables/models) | Contains a list of CatBoost models loaded into a LibraryBridge's memory along with time when it was loaded. | | [system.moves](/reference/system-tables/moves) | System table containing information about in-progress data part moves of MergeTree tables. Each data part movement is represented by a single row. | | [system.mutations](/reference/system-tables/mutations) | System table containing information about mutations of MergeTree tables and their progress. Each mutation command is represented by a single row. | | [system.named\_collections](/reference/system-tables/named_collections) | Contains a list of all named collections which were created via SQL query or parsed from configuration file. | | [system.numbers\_mt](/reference/system-tables/numbers_mt) | System table similar to `system.numbers` but reads are parallelized and numbers can be returned in any order. | | [system.numbers](/reference/system-tables/numbers) | System table containing a single UInt64 column named `number` that contains almost all the natural numbers starting from zero. | | [system.one](/reference/system-tables/one) | System table containing a single row with a single `dummy` UInt8 column containing the value 0. Similar to the `DUAL` table found in other DBMSs. | | [system.opentelemetry\_span\_log](/reference/system-tables/opentelemetry_span_log) | System table containing information about trace spans for executed queries. | | [system.part\_moves\_between\_shards](/reference/system-tables/part_moves_between_shards) | Contains information about parts which are currently in a process of moving between shards and their progress. | | [system.part\_log](/reference/system-tables/part_log) | System table containing information about events that occurred with data parts in the MergeTree family tables, such as adding or merging of data. | | [system.parts](/reference/system-tables/parts) | System table containing information about parts of MergeTree | | [system.parts\_columns](/reference/system-tables/parts_columns) | System table containing information about parts and columns of MergeTree tables. | | [system.predicate\_statistics\_log](/reference/system-tables/predicate_statistics_log) | System table containing sampled filter and index selectivity statistics collected from `MergeTree` read pipelines during query execution. | | [system.primes](/reference/system-tables/primes) | System table containing a single UInt64 column named `prime` that contains prime numbers in ascending order, starting from 2. | | [system.privileges](/reference/system-tables/privileges) | Contains a list of all available privileges that could be granted to a user or role. | | [system.processes](/reference/system-tables/processes) | System table used for implementing the `SHOW PROCESSLIST` query. | | [system.processors\_profile\_log](/reference/system-tables/processors_profile_log) | System table containing profiling information on the processors level (which can be found in `EXPLAIN PIPELINE`) | | [system.projection\_parts\_columns](/reference/system-tables/projection_parts_columns) | System table containing information about columns in projection parts for tables of the MergeTree family | | [system.projection\_parts](/reference/system-tables/projection_parts) | System table containing information about projection parts for tables of the MergeTree family. | | [system.projections](/reference/system-tables/projections) | System table containing information about existing projections in all tables. | | [system.query\_views\_log](/reference/system-tables/query_views_log) | System table containing information about the dependent views executed when running a query, for example, the view type or the execution time. | | [system.query\_condition\_cache](/reference/system-tables/query_condition_cache) | System table which shows the content of the query condition cache. | | [system.query\_thread\_log](/reference/system-tables/query_thread_log) | System table containing information about threads that execute queries, for example, thread name, thread start time, duration of query processing. | | [system.query\_metric\_log](/reference/system-tables/query_metric_log) | System table containing a history of memory and metric values from table `system.events` for individual queries, periodically flushed to disk. | | [system.query\_log](/reference/system-tables/query_log) | System table containing information about executed queries, for example, start time, duration of processing, error messages. | | [system.query\_cache](/reference/system-tables/query_cache) | System table which shows the content of the query cache. | | [system.quota\_usage](/reference/system-tables/quota_usage) | System table containing formation about quota usage by the current user such as how much of the quota is used and how much is left. | | [system.quota\_limits](/reference/system-tables/quota_limits) | System table containing information about maximums for all intervals of all quotas. Any number of rows or zero can correspond to one quota. | | [system.quotas\_usage](/reference/system-tables/quotas_usage) | System table containing formation about quota usage by all users. | | [system.quotas](/reference/system-tables/quotas) | System table containing information about quotas. | | [system.remote\_data\_paths](/reference/system-tables/remote_data_paths) | System table containing information about data files stored on remote disks such as S3 or Azure Blob Storage. | | [system.replicas](/reference/system-tables/replicas) | System table containing information about and status of replicated tables residing on the local server. Useful for monitoring. | | [system.replicated\_merge\_tree\_settings](/reference/system-tables/replicated_merge_tree_settings) | Contains a list of all ReplicatedMergeTree engine specific settings, their current and default values along with descriptions. You may change any of them in SETTINGS section in CREATE query. | | [system.replicated\_fetches](/reference/system-tables/replicated_fetches) | System table containing information about currently running background fetches. | | [system.replication\_queue](/reference/system-tables/replication_queue) | System table containing information about tasks from replication queues stored in ClickHouse Keeper, or ZooKeeper, for tables in the `ReplicatedMergeTree` family. | | [system.resources](/reference/system-tables/resources) | System table containing information about resources residing on the local server with one row for every resource. | | [system.rocksdb](/reference/system-tables/rocksdb) | Contains a list of metrics exposed from embedded RocksDB. | | [system.role\_grants](/reference/system-tables/role_grants) | System table containing the role grants for users and roles. | | [system.roles](/reference/system-tables/roles) | System table containing information about configured roles. | | [system.row\_policies](/reference/system-tables/row_policies) | System table containing filters for one particular table, as well as a list of roles and/or users which should use this row policy. | | [system.s3\_queue\_settings](/reference/system-tables/s3_queue_settings) | System table containing information about the settings of S3Queue tables. Available from server version `24.10`. | | [system.s3queue\_metadata\_cache](/reference/system-tables/s3queue_metadata_cache) | Contains in-memory state of S3Queue metadata and currently processed rows per file. | | [system.s3queue\_log](/reference/system-tables/s3queue_log) | Contains log entries with information about files processed by the S3Queue engine. | | It is safe to truncate or drop this table at any time. | | | [system.scheduler](/reference/system-tables/scheduler) | System table containing information about and status of scheduling nodes residing on the local server. | | [system.schema\_inference\_cache](/reference/system-tables/schema_inference_cache) | System table containing information about all cached file schemas. | | [system.server\_settings](/reference/system-tables/server_settings) | System table containing formation about global settings for the server, which are specified in `config.xml`. | | [system.session\_log](/reference/system-tables/session_log) | System table containing information about all successful and failed login and logout events. | | [system.settings](/reference/system-tables/settings) | System table containing information about session settings for current user. | | [system.settings\_profile\_elements](/reference/system-tables/settings_profile_elements) | System table which describes the content of the settings profile: constraints, roles and users that the setting applies to, parent settings profiles. | | [system.settings\_changes](/reference/system-tables/settings_changes) | System table containing information about setting changes in previous ClickHouse versions. | | [system.settings\_profiles](/reference/system-tables/settings_profiles) | System table which contains properties of configured setting profiles. | | [system.stack\_trace](/reference/system-tables/stack_trace) | System table which contains stack traces of all server threads. Allows developers to introspect the server state. | | [system.storage\_policies](/reference/system-tables/storage_policies) | System table containing information about storage policies and volumes which are defined in server configuration. | | [system.symbols](/reference/system-tables/symbols) | System table useful for C++ experts and ClickHouse engineers containing information for introspection of the `clickhouse` binary. | | [system.table\_engines](/reference/system-tables/table_engines) | System table containing descriptions of table engines supported by the server and the features they support. | | [system.table\_functions](/reference/system-tables/table_functions) | Contains a list of all available table functions with their descriptions. | | [system.tables](/reference/system-tables/tables) | System table containing metadata of each table that the server knows about. | | [system.text\_log](/reference/system-tables/text_log) | System table containing logging entries. | | [system.time\_zones](/reference/system-tables/time_zones) | System table containing a list of time zones that are supported by the ClickHouse server. | | [system.tokenizers](/reference/system-tables/tokenizers) | System table which shows all available tokenizers. | | [system.trace\_log](/reference/system-tables/trace_log) | System table containing stack traces collected by the sampling query profiler. | | [system.transactions](/reference/system-tables/transactions) | Contains a list of transactions and their state. | | [system.transactions\_info\_log](/reference/system-tables/transactions_info_log) | Contains information about all transactions executed on a current server. | | It is safe to truncate or drop this table at any time. | | | [system.unicode](/reference/system-tables/unicode) | System table containing a list of Unicode characters and their properties. | | [system.user\_processes](/reference/system-tables/user_processes) | System table containing information useful for an overview of memory usage and ProfileEvents of users. | | [system.user\_directories](/reference/system-tables/user_directories) | Contains the information about configured user directories - directories on the file system from which ClickHouse server is allowed to read user provided data. | | [system.user\_defined\_functions](/reference/system-tables/user_defined_functions) | System table containing loading status and configuration metadata for User-Defined Functions (UDFs). | | [system.users](/reference/system-tables/users) | System table containing a list of user accounts configured on the server. | | [system.view\_refreshes](/reference/system-tables/view_refreshes) | System table containing information about Refreshable Materialized Views. | | [system.warnings](/reference/system-tables/system_warnings) | This table contains warning messages about clickhouse server. | | [system.warnings](/reference/system-tables/warnings) | Contains warnings about server configuration to be displayed by clickhouse-client right after it connects to the server. | | [system.workloads](/reference/system-tables/workloads) | System table containing information for workloads residing on the local server. | | [system.zeros](/reference/system-tables/zeros) | Produces unlimited number of non-materialized zeros. | | [system.zeros\_mt](/reference/system-tables/zeros_mt) | Multithreaded version of system.zeros. | | [system.zookeeper\_watches](/reference/system-tables/zookeeper_watches) | System table showing currently active ZooKeeper watches registered by this ClickHouse server. | | [system.zookeeper\_info](/reference/system-tables/zookeeper_info) | System table which outputs introspection of all available keeper nodes. | | [system.zookeeper\_log](/reference/system-tables/zookeeper_log) | System table containing information about the parameters of the request to the ZooKeeper server and the response from it. | | [system.zookeeper\_connection](/reference/system-tables/zookeeper_connection) | System table which exists only if ZooKeeper is configured. Shows current connections to ZooKeeper (including auxiliary ZooKeepers). | | [system.zookeeper\_connection\_log](/reference/system-tables/zookeeper_connection_log) | Shows the history of ZooKeeper connections (including auxiliary ZooKeepers). | | [system.zookeeper](/reference/system-tables/zookeeper) | System table which exists only if ClickHouse Keeper or ZooKeeper are configured. It exposes data from the Keeper cluster defined in the config. |