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5.5 is slower than 5.3 on a DBT-3 query#1, MyISAM storage engine.
Profiling shows that 5.5 does many str_to_datetime calls.
The query:
select
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l_returnflag,
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l_linestatus,
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sum(l_quantity) as sum_qty,
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sum(l_extendedprice) as sum_base_price,
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sum(l_extendedprice * (1 - l_discount)) as sum_disc_price,
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sum(l_extendedprice * (1 - l_discount) * (1 + l_tax)) as sum_charge,
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avg(l_quantity) as avg_qty,
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avg(l_extendedprice) as avg_price,
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avg(l_discount) as avg_disc,
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count(*) as count_order
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from
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lineitem
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where
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l_shipdate <= date_sub('1998-12-01', interval 79 day)
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group by
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l_returnflag,
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l_linestatus
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order by
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l_returnflag,
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l_linestatus;
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See comments to MDEV-4150 for analysis. MySQL-5.5's "constant item caching" interferes with get_datetime_value()'s caching mechanism, as a result, datetime value is cached in its string form, and we get string->datetime conversion done for every row.
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lineitem_small.sql.gz