Mysql 优化——分析表读写和sql效率问题

上次我们说到mysql的一些sql查询方面的优化，包括查看explain执行计划，分析索引等等。  今天我们分享一些 分析mysql表读写、索引等等操作的sql语句。

闲话不多说，直接上代码：

-- 反映表的读写压力SELECT file_name AS file,       count_read,       sum_number_of_bytes_read AS total_read,       count_write,       sum_number_of_bytes_write AS total_written,       (sum_number_of_bytes_read + sum_number_of_bytes_write) AS total  FROM performance_schema.file_summary_by_instanceORDER BY sum_number_of_bytes_read+ sum_number_of_bytes_write DESC;-- 反映文件的延迟SELECT (file_name) AS file,       count_star AS total,       CONCAT(ROUND(sum_timer_wait / 3600000000000000, 2), 'h') AS total_latency,       count_read,        CONCAT(ROUND(sum_timer_read / 1000000000000, 2), 's') AS read_latency,       count_write,       CONCAT(ROUND(sum_timer_write / 3600000000000000, 2), 'h')AS write_latency  FROM performance_schema.file_summary_by_instanceORDER BY sum_timer_wait DESC;-- table 的读写延迟SELECT object_schema AS table_schema,             object_name AS table_name,             count_star AS total,              CONCAT(ROUND(sum_timer_wait / 3600000000000000, 2), 'h') as total_latency,              CONCAT(ROUND((sum_timer_wait / count_star) / 1000000, 2), 'us') AS avg_latency,              CONCAT(ROUND(max_timer_wait / 1000000000, 2), 'ms') AS max_latency  FROM performance_schema.objects_summary_global_by_type       ORDER BY sum_timer_wait DESC;-- 查看表操作频度SELECT object_schema AS table_schema,            object_name AS table_name,            count_star AS rows_io_total,            count_read AS rows_read,            count_write AS rows_write,            count_fetch AS rows_fetchs,            count_insert AS rows_inserts,            count_update AS rows_updates,            count_delete AS rows_deletes,             CONCAT(ROUND(sum_timer_fetch / 3600000000000000, 2), 'h') AS fetch_latency,             CONCAT(ROUND(sum_timer_insert / 3600000000000000, 2), 'h') AS insert_latency,             CONCAT(ROUND(sum_timer_update / 3600000000000000, 2), 'h') AS update_latency,             CONCAT(ROUND(sum_timer_delete / 3600000000000000, 2), 'h') AS delete_latency     FROM performance_schema.table_io_waits_summary_by_table        ORDER BY sum_timer_wait DESC ;-- 索引状况SELECT OBJECT_SCHEMA AS table_schema,               OBJECT_NAME AS table_name,               INDEX_NAME as index_name,               COUNT_FETCH AS rows_fetched,               CONCAT(ROUND(SUM_TIMER_FETCH / 3600000000000000, 2), 'h') AS select_latency,               COUNT_INSERT AS rows_inserted,               CONCAT(ROUND(SUM_TIMER_INSERT / 3600000000000000, 2), 'h') AS insert_latency,               COUNT_UPDATE AS rows_updated,               CONCAT(ROUND(SUM_TIMER_UPDATE / 3600000000000000, 2), 'h') AS update_latency,               COUNT_DELETE AS rows_deleted,                CONCAT(ROUND(SUM_TIMER_DELETE / 3600000000000000, 2), 'h')AS delete_latencyFROM performance_schema.table_io_waits_summary_by_index_usageWHERE index_name IS NOT NULLORDER BY sum_timer_wait DESC;-- 全表扫描情况SELECT object_schema,       object_name,       count_read AS rows_full_scanned  FROM performance_schema.table_io_waits_summary_by_index_usageWHERE index_name IS NULL   AND count_read > 0ORDER BY count_read DESC;-- 没有使用的indexSELECT object_schema,        object_name,        index_name   FROM performance_schema.table_io_waits_summary_by_index_usage  WHERE index_name IS NOT NULL    AND count_star = 0    AND object_schema not in  ('mysql','v_monitor')   AND index_name <> 'PRIMARY'  ORDER BY object_schema, object_name;-- 糟糕的sql问题摘要SELECT (DIGEST_TEXT) AS query,        SCHEMA_NAME AS db,        IF(SUM_NO_GOOD_INDEX_USED > 0 OR SUM_NO_INDEX_USED > 0, '*', '') AS full_scan,        COUNT_STAR AS exec_count,        SUM_ERRORS AS err_count,        SUM_WARNINGS AS warn_count,        (SUM_TIMER_WAIT) AS total_latency,        (MAX_TIMER_WAIT) AS max_latency,        (AVG_TIMER_WAIT) AS avg_latency,        (SUM_LOCK_TIME) AS lock_latency,        format(SUM_ROWS_SENT,0) AS rows_sent,        ROUND(IFNULL(SUM_ROWS_SENT / NULLIF(COUNT_STAR, 0), 0)) AS rows_sent_avg,        SUM_ROWS_EXAMINED AS rows_examined,        ROUND(IFNULL(SUM_ROWS_EXAMINED / NULLIF(COUNT_STAR, 0), 0))  AS rows_examined_avg,        SUM_CREATED_TMP_TABLES AS tmp_tables,        SUM_CREATED_TMP_DISK_TABLES AS tmp_disk_tables,        SUM_SORT_ROWS AS rows_sorted,        SUM_SORT_MERGE_PASSES AS sort_merge_passes,        DIGEST AS digest,        FIRST_SEEN AS first_seen,        LAST_SEEN as last_seen   FROM performance_schema.events_statements_summary_by_digest dwhere dORDER BY SUM_TIMER_WAIT DESClimit 20;

掌握这些sql，你能轻松知道你的库那些表存在问题，然后考虑怎么去优化。   

另外，有些博友问我为何每次博客不写全面，比如为何优化什么的，我想说的是，大部分人只关心如何用，至于为什么，其实可以自己去找答案，而且我也没太多时间去写。至于优不优质博客我不在乎，这些算是我的自己的日常积累吧