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The symptoms were: take a server with no activity and a table that's not in the buffer pool. Run a query that reads the whole table and observe that r_engine_stats.pages_read_count shows about 2% of the table was read. Who reads the rest? The cause was that page prefetching done inside InnoDB was not counted. This counts page prefetch requests made in buf_read_ahead_random() and buf_read_ahead_linear() and makes them visible in: - ANALYZE: r_engine_stats.pages_prefetch_read_count - Slow Query Log: Pages_prefetched: This patch intentionally doesn't attempt to count the time to read the prefetched pages: * there's no obvious place where one can do it * prefetch reads may be done in parallel (right?), it is not clear how to count the time in this case.
31 lines
1.4 KiB
HTML
31 lines
1.4 KiB
HTML
# Common extensions to the slow query log
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--let grep_pattern = ^# Thread_id: .+ Schema: .+ QC_hit: (Yes|No)\$
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--let log_expected_matches = $log_slow_verbosity_expected_matches
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--source include/log_grep.inc
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--let grep_pattern = ^# Query_time: \d+\.\d+ Lock_time: \d+\.\d+ Rows_sent: \d+ Rows_examined: \d+\$
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--source include/log_grep.inc
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--let grep_pattern = ^# Rows_affected: \d+ Bytes_sent: \d+\$
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--source include/log_grep.inc
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# Query plan
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--let log_expected_matches = $log_slow_verbosity_queryplan_expected_matches
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--let grep_pattern = ^# Full_scan: (Yes|No) Full_join: (Yes|No) Tmp_table: (Yes|No) Tmp_table_on_disk: (Yes|No)\$
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--source include/log_grep.inc
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--let grep_pattern = ^# Filesort: (Yes|No) Filesort_on_disk: (Yes|No) Merge_passes: \d+\ Priority_queue: (Yes|No)\$
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--source include/log_grep.inc
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# Temp tables
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--let log_expected_matches = $log_slow_verbosity_tmptable_expected_matches
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--source include/log_grep.inc
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--let grep_pattern = ^# Tmp_tables: \d+ Tmp_disk_tables: \d+\$
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--source include/log_grep.inc
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# InnoDB/Engines
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--let log_expected_matches = $log_slow_verbosity_innodb_expected_matches
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--let grep_pattern = ^# Pages_accessed: \d+ Pages_read: \d+ Pages_prefetched: \d+ Pages_updated: \d+ Old_rows_read: \d+\$
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--source include/log_grep.inc
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--let grep_pattern = ^# Pages_read_time: \d+\.\d+ Engine_time: \d+\.\d+\$
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--source include/log_grep.inc
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