# Performance Schema - [Performance Schema Digests](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-digests.md): Statement digests aggregate statistics for similar queries by removing specific data values, allowing you to identify performance patterns across statement types. - [Performance Schema Overview](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-overview.md): The Performance Schema is a feature for monitoring server performance that inspects internal execution details at a low level with minimal overhead. - [Performance Schema Status Variables](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-status-variables.md): This page lists status variables that track the internal health of the Performance Schema, such as counters for lost events due to memory constraints. - [Performance Schema System Variables](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-system-variables.md): Configure the Performance Schema using these system variables to control buffer sizes, set instrumentation limits, and enable specific consumers at startup. - [Performance Schema Tables](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables.md): Explore the tables in the performance\_schema database, which expose granular metrics on server events, locks, threads, and I/O for detailed performance analysis. - [List of Performance Schema Tables](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/list-of-performance-schema-tables.md): Browse the List of Performance Schema Tables in MariaDB. Access a comprehensive index of tables and descriptions to assist in monitoring server performance. - [Performance Schema accounts Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-accounts-table.md): The Performance Schema accounts table stores statistics on current and total connections for each client account connecting to the server. - [Performance Schema cond\_instances Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-cond_instances-table.md): The cond\_instances table lists all active condition objects (internal code mechanisms for thread signaling) currently on the server. - [Performance Schema events\_stages\_current Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_stages_current-table.md): The events\_stages\_current table shows the current stage event for each thread, including timer information and nesting details. - [Performance Schema events\_stages\_history Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_stages_history-table.md): This table records the ten most recent completed stage events per thread, useful for analyzing recent thread activity. - [Performance Schema events\_stages\_history\_long Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_stages_history_long-table.md): The events\_stages\_history\_long table stores the most recent 10,000 completed stage events globally, providing a deeper history than per-thread tables. - [Performance Schema events\_stages\_summary\_by\_account\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_stages_summary_by_account_by_event_name-table.md): This table summarizes stage events aggregated by the client account and the specific event name, showing counts and wait times. - [Performance Schema events\_stages\_summary\_by\_host\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_stages_summary_by_host_by_event_name-table.md): This table summarizes stage events aggregated by the client host and the event name, allowing performance analysis per host. - [Performance Schema events\_stages\_summary\_by\_thread\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_stages_summary_by_thread_by_event_name-table.md): This table summarizes stage events aggregated by thread and event name, providing granular statistics on thread execution stages. - [Performance Schema events\_stages\_summary\_by\_user\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_stages_summary_by_user_by_event_name-table.md): This table summarizes stage events aggregated by user name and event name, helping to identify users with resource-intensive stages. - [Performance Schema events\_stages\_summary\_global\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_stages_summary_global_by_event_name-table.md): This table summarizes stage events aggregated by the client host and the event name, allowing performance analysis per host. - [Performance Schema events\_statements\_current Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_statements_current-table.md): The events\_statements\_current table displays the current statement event for each thread, including SQL text, timer stats, and error codes. - [Performance Schema events\_statements\_history Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_statements_history-table.md): This table records the ten most recent completed statement events per thread, offering a short-term history of executed SQL statements. - [Performance Schema events\_statements\_history\_long Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_statements_history_long-table.md): The events\_statements\_history\_long table stores the most recent 10,000 completed statement events globally, providing extensive query history. - [Performance Schema events\_statements\_summary\_by\_account\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_statements_summary_by_account_by_event_name-table.md): This table summarizes statement events aggregated by client account and event name, detailing execution counts and timer statistics. - [Performance Schema events\_statements\_summary\_by\_digest Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_statements_summary_by_digest-table.md): This table aggregates statement events by schema and digest, providing execution counts, latency, and locking statistics for normalized queries. - [Performance Schema events\_statements\_summary\_by\_host\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_statements_summary_by_host_by_event_name-table.md): This table summarizes statement events aggregated by client host and event name, showing execution frequency and wait times per host. - [Performance Schema events\_statements\_summary\_by\_program Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_statements_summary_by_program-table.md): This table provides summary statistics for statements executed within stored programs, such as procedures, functions, triggers, and events. - [Performance Schema events\_statements\_summary\_by\_thread\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_statements_summary_by_thread_by_event_name-table.md): This table summarizes statement events aggregated by thread and event name, allowing analysis of statement execution per individual thread. - [Performance Schema events\_statements\_summary\_by\_user\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_statements_summary_by_user_by_event_name-table.md): This table summarizes statement events aggregated by user name and event name, helping to identify users executing specific statement types. - [Performance Schema events\_statements\_summary\_global\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_statements_summary_global_by_event_name-table.md): This table provides a global summary of statement events aggregated by event name, showing total execution counts and wait times for the server. - [Performance Schema events\_transactions\_current Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_transactions_current-table.md): The events\_transactions\_current table displays the current transaction event for each thread, including state, isolation level, and GTID. - [Performance Schema events\_transactions\_history Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_transactions_history-table.md): This table records the ten most recent completed stage events per thread, useful for analyzing recent thread activity. - [Performance Schema events\_transactions\_history\_long Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_transactions_history_long-table.md): The events\_stages\_history\_long table stores the most recent 10,000 completed stage events globally, providing a deeper history than per-thread tables. - [Performance Schema events\_transactions\_summary\_by\_account\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_transactions_summary_by_account_by_event_name-tab.md): This table summarizes stage events aggregated by the client account and the specific event name, showing counts and wait times. - [Performance Schema events\_transactions\_summary\_by\_host\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_transactions_summary_by_host_by_event_name-table.md): This table summarizes stage events aggregated by the client host and the event name, allowing performance analysis per host. - [Performance Schema events\_transactions\_summary\_by\_thread\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_transactions_summary_by_thread_by_event_name-tabl.md): This table summarizes stage events aggregated by thread and event name, providing granular statistics on thread execution stages. - [Performance Schema events\_transactions\_summary\_by\_user\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_transactions_summary_by_user_by_event_name-table.md): This table summarizes stage events aggregated by user name and event name, helping to identify users with resource-intensive stages. - [Performance Schema events\_transactions\_summary\_global\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_transactions_summary_global_by_event_name-table.md): This table provides a global summary of statement events aggregated by event name, showing total execution counts and wait times for the server. - [Performance Schema events\_waits\_current Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_waits_current-table.md): The events\_waits\_current table displays the most recent wait event for each thread, including timer and object information. - [Performance Schema events\_waits\_history Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_waits_history-table.md): This table records the ten most recent completed wait events per thread, useful for diagnosing recent latency issues. - [Performance Schema events\_waits\_history\_long Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_waits_history_long-table.md): The events\_waits\_history\_long table stores the most recent 10,000 completed wait events globally, autosized at startup. - [Performance Schema events\_waits\_summary\_by\_account\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_waits_summary_by_account_by_event_name-table.md): This table summarizes wait events aggregated by client account and event name, providing statistics on wait times and execution counts. - [Performance Schema events\_waits\_summary\_by\_host\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_waits_summary_by_host_by_event_name-table.md): This table summarizes wait events aggregated by client host and event name, helping to analyze wait latencies on a per-host basis. - [Performance Schema events\_waits\_summary\_by\_instance Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_waits_summary_by_instance-table.md): This table summarizes wait events per instrument instance, allowing detailed analysis of specific locks, mutexes, or conditions. - [Performance Schema events\_waits\_summary\_by\_thread\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_waits_summary_by_thread_by_event_name-table.md): This table summarizes wait events aggregated by thread and event name, useful for pinpointing threads experiencing high wait times. - [Performance Schema events\_waits\_summary\_by\_user\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_waits_summary_by_user_by_event_name-table.md): This table summarizes wait events aggregated by user name and event name, helping to identify users triggering significant wait events. - [Performance Schema events\_waits\_summary\_global\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-events_waits_summary_global_by_event_name-table.md): This table provides a global summary of wait events aggregated by event name, showing total server-wide wait statistics. - [Performance Schema file\_instances Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-file_instances-table.md): The file\_instances table lists all file objects currently open by the server, including filenames and the number of open handles. - [Performance Schema file\_summary\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-file_summary_by_event_name-table.md): This table summarizes file I/O events aggregated by event name, detailing read/write counts and bytes transferred for each file type. - [Performance Schema file\_summary\_by\_instance Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-file_summary_by_instance-table.md): This table summarizes file I/O events aggregated by file instance, providing granular I/O statistics for individual files. - [Performance Schema global\_status Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-global_status-table.md): The global\_status table provides a persistent view of global server status variables, aggregating statistics across all threads. - [Performance Schema host\_cache Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-host_cache-table.md): The host\_cache table exposes the internal host cache contents, including IP-to-hostname resolution details and connection error counters. - [Performance Schema hosts Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-hosts-table.md): The hosts table contains aggregated connection statistics for each client host, including counts for current and total historical connections. - [Performance Schema memory\_summary\_by\_account\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-memory_summary_by_account_by_event_name-table.md): This table summarizes memory usage events aggregated by client account and event name, tracking current usage and high-water marks. - [Performance Schema memory\_summary\_by\_host\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-memory_summary_by_host_by_event_name-table.md): This table summarizes memory usage events aggregated by client host and event name, helping to analyze memory consumption patterns per host. - [Performance Schema memory\_summary\_by\_thread\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-memory_summary_by_thread_by_event_name-table.md): This table summarizes memory usage events aggregated by thread and event name, allowing for detailed memory profiling of individual threads. - [Performance Schema memory\_summary\_by\_user\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-memory_summary_by_user_by_event_name-table.md): This table summarizes memory usage events aggregated by user name and event name, useful for identifying users with high memory footprints. - [Performance Schema memory\_summary\_global\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-memory_summary_global_by_event_name-table.md): This table provides a global summary of memory usage events aggregated by event name, showing total memory allocation across the server. - [Performance Schema metadata\_locks Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-metadata_locks-table.md): The metadata\_locks table lists currently held and requested metadata locks, which protect database object definitions from concurrent modification. - [Performance Schema mutex\_instances Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-mutex_instances-table.md): The mutex\_instances table lists all active mutexes (mutual exclusions) instrumented by the Performance Schema, showing their locked state. - [Performance Schema objects\_summary\_global\_by\_type Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-objects_summary_global_by_type-table.md): This table aggregates usage statistics for objects (tables, events, etc.) by type, schema, and name, showing global access counts and timers. - [Performance Schema performance\_timers Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-performance_timers-table.md): The performance\_timers table lists available event timers (cycle, nanosecond, microsecond, millisecond) and their overhead characteristics. - [Performance Schema prepared\_statements\_instances Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-prepared_statements_instances-table.md): The rwlock\_instances table lists all active read-write lock instances, showing the write-lock owner and the number of waiting readers or writers. - [Performance Schema replication\_applier\_configuration Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-replication_applier_configuration-table.md): This table displays the configuration parameters used by the replica to connect to the primary server, such as host, port, and user credentials. - [Performance Schema replication\_applier\_status Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-replication_applier_status-table.md): The replication\_applier\_status\_by\_worker table provides status information for each worker thread involved in parallel replication. - [Performance Schema replication\_applier\_status\_by\_coordinator Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-replication_applier_status_by_coordinator-table.md): This table shows the status of the coordinator thread when parallel replication is enabled, detailing the distribution of transactions to workers. - [Performance Schema replication\_applier\_status\_by\_worker Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-replication_applier_status_by_worker-table.md): The replication\_applier\_status\_by\_worker table provides status information for each worker thread involved in parallel replication. - [Performance Schema replication\_connection\_configuration Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-replication_connection_configuration-table.md): This table displays the configuration parameters used by the replica to connect to the primary server, such as host, port, and user credentials. - [Performance Schema rwlock\_instances Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-rwlock_instances-table.md): The rwlock\_instances table lists all active read-write lock instances, showing the write-lock owner and the number of waiting readers or writers. - [Performance Schema session\_account\_connect\_attrs Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-session_account_connect_attrs-table.md): This table exposes connection attributes for the current session's account, providing metadata passed by the client application for identification. - [Performance Schema session\_connect\_attrs Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-session_connect_attrs-table.md): The session\_connect\_attrs table lists connection attributes for the current session, offering details about the client library and environment. - [Performance Schema session\_status Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-session_status-table.md): The session\_status table displays status variable values for the current session, providing data equivalent to the SHOW SESSION STATUS statement. - [Performance Schema setup\_actors Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-setup_actors-table.md): The setup\_actors table configures which foreground threads (users/hosts) are monitored, allowing for targeted instrumentation of specific accounts. - [Performance Schema setup\_consumers Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-setup_consumers-table.md): The setup\_consumers table controls which consumers (destinations) are enabled to store event data, managing the flow of metrics to history tables. - [Performance Schema setup\_instruments Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-setup_instruments-table.md): The setup\_instruments table lists all supported instruments, allowing administrators to enable collection and configure timing for specific events. - [Performance Schema setup\_objects Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-setup_objects-table.md): The setup\_objects table configures which database objects (tables, stored programs) are instrumented, enabling filtering by schema or name. - [Performance Schema setup\_timers Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-setup_timers-table.md): The setup\_timers table defines the timer type (e.g., NANOSECOND, MICROSECOND) used for each instrument class within the Performance Schema. - [Performance Schema socket\_instances Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-socket_instances-table.md): The socket\_instances table lists active network socket connections, providing details such as the IP address, port, and state of each socket. - [Performance Schema socket\_summary\_by\_event\_name Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-socket_summary_by_event_name-table.md): This table summarizes socket I/O events aggregated by event name, showing execution counts and wait times for operations like send and receive. - [Performance Schema socket\_summary\_by\_instance Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-socket_summary_by_instance-table.md): This table summarizes socket I/O events per socket instance, allowing for traffic analysis and latency monitoring of individual connections. - [Performance Schema status\_by\_account Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-status_by_account-table.md): The status\_by\_account table aggregates session status variables by client account, showing cumulative counters for specific user-host combinations. - [Performance Schema status\_by\_host Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-status_by_host-table.md): The status\_by\_host table aggregates session status variables by client host, useful for tracking activity levels from specific application servers. - [Performance Schema status\_by\_thread Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-status_by_thread-table.md): The status\_by\_thread table lists session status variables for each active thread, effectively providing a "SHOW SESSION STATUS" for every connection. - [Performance Schema status\_by\_user Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-status_by_user-table.md): The status\_by\_user table aggregates session status variables by user name, summarizing activity across all connections for a specific user identity. - [Performance Schema table\_handles Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-table_handles-table.md): The table\_handles table lists all open table handles, showing which threads are currently accessing which table instances and the locks they hold. - [Performance Schema table\_io\_waits\_summary\_by\_index\_usage Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-table_io_waits_summary_by_index_usage-table.md): This table aggregates I/O wait statistics by index, helping to identify which indexes handle the most traffic or are causing latency. - [Performance Schema table\_io\_waits\_summary\_by\_table Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-table_io_waits_summary_by_table-table.md): This table summarizes I/O wait events by table, detailing the frequency and latency of fetch, insert, update, and delete operations. - [Performance Schema table\_lock\_waits\_summary\_by\_table Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-table_lock_waits_summary_by_table-table.md): This table aggregates table lock wait events, allowing administrators to identify tables experiencing high contention due to locking. - [Performance Schema threads Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-threads-table.md): The threads table lists all instrumented threads, mapping internal thread IDs to process IDs and providing execution status for every thread. - [Performance Schema users Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-users-table.md): The users table tracks connection statistics aggregated by user name, including current active connections and total historical connections. - [Performance Schema user\_variables\_by\_thread Table](https://mariadb.com/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-user_variables_by_thread-table.md): This table exposes user-defined variables set within active threads, allowing inspection of custom variables across all sessions. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://mariadb.com/docs/server/reference/system-tables/performance-schema.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.