Mysql 优化——分析表读写和sql效率问题

gdrocket

　　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_instance
　　ORDER 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_instance
　　ORDER 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_latency
　　FROM performance_schema.table_io_waits_summary_by_index_usage
　　WHERE index_name IS NOT NULL
　　ORDER 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_usage
　　WHERE index_name IS NULL
　　AND count_read > 0
　　ORDER BY count_read DESC;
　　-- 没有使用的index
　　SELECT 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 d
　　where d
　　ORDER BY SUM_TIMER_WAIT DESC
　　limit 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