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Advisor system

Possible performance issues

Issue:
long_query_time is set to 10 seconds or more, thus only slow queries that take above 10 seconds are logged.
Recommendation:
It is suggested to set long_query_time to a lower value, depending on your environment. Usually a value of 1-5 seconds is suggested.
Justification:
long_query_time is currently set to 10s.
Used variable / formula:
long_query_time
Test:
value >= 10
Issue:
The slow query log is disabled.
Recommendation:
Enable slow query logging by setting slow_query_log to 'ON'. This will help troubleshooting badly performing queries.
Justification:
slow_query_log is set to 'OFF'
Used variable / formula:
slow_query_log
Test:
value == 'OFF'
Issue:
Version is compiled from source, not a MySQL official binary.
Recommendation:
If you did not compile from source, you may be using a package modified by a distribution. The MySQL manual only is accurate for official MySQL binaries, not any package distributions (such as RedHat, Debian/Ubuntu etc).
Justification:
'source' found in version_comment
Used variable / formula:
version_comment
Test:
preg_match('/source/i',value)
Issue:
There are too many joins without indexes.
Recommendation:
This means that joins are doing full table scans. Adding indexes for the columns being used in the join conditions will greatly speed up table joins.
Justification:
Table joins average: 1.44 per hour, this value should be less than 1 per hour
Used variable / formula:
(Select_range_check + Select_scan + Select_full_join) / Uptime
Test:
value * 60 * 60 > 1
Issue:
The rate of reading the next table row is high.
Recommendation:
This indicates that many queries are doing full table scans. Add indexes where applicable.
Justification:
Rate of reading next table row: 29.7 per hour, this value should be less than 1 per hour
Used variable / formula:
Handler_read_rnd_next / Uptime
Test:
value * 60 * 60 > 1
Issue:
MyISAM key buffer (index cache) % used is low.
Recommendation:
You may need to decrease the size of key_buffer_size, re-examine your tables to see if indexes have been removed, or examine queries and expectations about what indexes are being used.
Justification:
max % MyISAM key buffer ever used: 0%, this value should be above 95%
Used variable / formula:
Key_blocks_used * key_cache_block_size / key_buffer_size * 100
Test:
value < 95
Issue:
The % of indexes that use the MyISAM key buffer is low.
Recommendation:
You may need to increase key_buffer_size.
Justification:
Index reads from memory: 93%, this value should be above 95%
Used variable / formula:
100 - (Key_reads / Key_read_requests * 100)
Test:
value < 95
Issue:
Too many connections are aborted.
Recommendation:
Connections are usually aborted when they cannot be authorized. This article might help you track down the source.
Justification:
9% of all connections are aborted. This value should be below 1%
Used variable / formula:
Aborted_connects / Connections * 100
Test:
value > 1
Issue:
The query cache is not enabled.
Recommendation:
The query cache is known to greatly improve performance if configured correctly. Enable it by setting query_cache_size to a 2 digit MiB value and setting query_cache_type to 'ON'. Note: If you are using memcached, ignore this recommendation.
Justification:
query_cache_size is set to 0 or query_cache_type is set to 'OFF'
Used variable / formula:
query_cache_size
Test:
value == 0 || query_cache_type == 'OFF' || query_cache_type == '0'