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26.4.3 sys Schema Views The host_summary and x$host_summary Views The host_summary_by_file_io and x$host_summary_by_file_io Views The host_summary_by_file_io_type and x$host_summary_by_file_io_type Views The host_summary_by_stages and x$host_summary_by_stages Views The host_summary_by_statement_latency and x$host_summary_by_statement_latency Views The host_summary_by_statement_type and x$host_summary_by_statement_type Views The innodb_buffer_stats_by_schema and x$innodb_buffer_stats_by_schema Views The innodb_buffer_stats_by_table and x$innodb_buffer_stats_by_table Views The innodb_lock_waits and x$innodb_lock_waits Views The io_by_thread_by_latency and x$io_by_thread_by_latency Views The io_global_by_file_by_bytes and x$io_global_by_file_by_bytes Views The io_global_by_file_by_latency and x$io_global_by_file_by_latency Views The io_global_by_wait_by_bytes and x$io_global_by_wait_by_bytes Views The io_global_by_wait_by_latency and x$io_global_by_wait_by_latency Views The latest_file_io and x$latest_file_io Views The memory_by_host_by_current_bytes and x$memory_by_host_by_current_bytes Views The memory_by_thread_by_current_bytes and x$memory_by_thread_by_current_bytes Views The memory_by_user_by_current_bytes and x$memory_by_user_by_current_bytes Views The memory_global_by_current_bytes and x$memory_global_by_current_bytes Views The memory_global_total and x$memory_global_total Views The metrics View The processlist and x$processlist Views The ps_check_lost_instrumentation View The schema_auto_increment_columns View The schema_index_statistics and x$schema_index_statistics Views The schema_object_overview View The schema_redundant_indexes and x$schema_flattened_keys Views The schema_table_lock_waits and x$schema_table_lock_waits Views The schema_table_statistics and x$schema_table_statistics Views The schema_table_statistics_with_buffer and x$schema_table_statistics_with_buffer Views The schema_tables_with_full_table_scans and x$schema_tables_with_full_table_scans Views The schema_unused_indexes View The session and x$session Views The session_ssl_status View The statement_analysis and x$statement_analysis Views The statements_with_errors_or_warnings and x$statements_with_errors_or_warnings Views The statements_with_full_table_scans and x$statements_with_full_table_scans Views The statements_with_runtimes_in_95th_percentile and x$statements_with_runtimes_in_95th_percentile Views The statements_with_sorting and x$statements_with_sorting Views The statements_with_temp_tables and x$statements_with_temp_tables Views The user_summary and x$user_summary Views The user_summary_by_file_io and x$user_summary_by_file_io Views The user_summary_by_file_io_type and x$user_summary_by_file_io_type Views The user_summary_by_stages and x$user_summary_by_stages Views The user_summary_by_statement_latency and x$user_summary_by_statement_latency Views The user_summary_by_statement_type and x$user_summary_by_statement_type Views The version View The wait_classes_global_by_avg_latency and x$wait_classes_global_by_avg_latency Views The wait_classes_global_by_latency and x$wait_classes_global_by_latency Views The waits_by_host_by_latency and x$waits_by_host_by_latency Views The waits_by_user_by_latency and x$waits_by_user_by_latency Views The waits_global_by_latency and x$waits_global_by_latency Views

The following sections describe sys schema views.

The sys schema contains many views that summarize Performance Schema tables in various ways. Most of these views come in pairs, such that one member of the pair has the same name as the other member, plus a x$ prefix. For example, the host_summary_by_file_io view summarizes file I/O grouped by host and displays latencies converted from picoseconds to more readable values (with units);

mysql> SELECT * FROM sys.host_summary_by_file_io;
| host       | ios   | io_latency |
| localhost  | 67570 | 5.38 s     |
| background |  3468 | 4.18 s     |

The x$host_summary_by_file_io view summarizes the same data but displays unformatted picosecond latencies:

mysql> SELECT * FROM sys.x$host_summary_by_file_io;
| host       | ios   | io_latency    |
| localhost  | 67574 | 5380678125144 |
| background |  3474 | 4758696829416 |

The view without the x$ prefix is intended to provide output that is more user friendly and easier to read. The view with the x$ prefix that displays the same values in raw form is intended more for use with other tools that perform their own processing on the data.

Views without the x$ prefix differ from the corresponding x$ views in these ways: