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Bug#35745: SELECT COUNT(*) is not correct for some partitioned tables.
problem was that ha_partition::records was not implemented, thus using the default handler::records, which is not correct if the engine does not support HA_STATS_RECORDS_IS_EXACT. Solution was to implement ha_partition::records as a wrapper around the underlying partitions records. The rows column in explain partitions will now include the total number of records in the partitioned table. (recommit after removing out-commented code)
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@ -57,13 +57,13 @@ id select_type table partitions type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 pnull system NULL NULL NULL NULL 1
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explain partitions select * from t1 where a >= 0;
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id select_type table partitions type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 p0,p1 ALL NULL NULL NULL NULL 2 Using where
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1 SIMPLE t1 p0,p1 ALL NULL NULL NULL NULL 3 Using where
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explain partitions select * from t1 where a < 0;
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id select_type table partitions type possible_keys key key_len ref rows Extra
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1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
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explain partitions select * from t1 where a <= 0;
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id select_type table partitions type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 pnull,p0 ALL NULL NULL NULL NULL 2 Using where
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1 SIMPLE t1 pnull,p0 ALL NULL NULL NULL NULL 3 Using where
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explain partitions select * from t1 where a > 1;
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id select_type table partitions type possible_keys key key_len ref rows Extra
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1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
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@ -96,16 +96,16 @@ select * from t1 where a > 1;
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a b
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explain partitions select * from t1 where a is null;
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id select_type table partitions type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 pnull_pnullsp0,pnull_pnullsp1 ALL NULL NULL NULL NULL 2 Using where
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1 SIMPLE t1 pnull_pnullsp0,pnull_pnullsp1 ALL NULL NULL NULL NULL 6 Using where
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explain partitions select * from t1 where a >= 0;
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id select_type table partitions type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 p0_p0sp0,p0_p0sp1,p1_p1sp0,p1_p1sp1 ALL NULL NULL NULL NULL 4 Using where
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1 SIMPLE t1 p0_p0sp0,p0_p0sp1,p1_p1sp0,p1_p1sp1 ALL NULL NULL NULL NULL 6 Using where
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explain partitions select * from t1 where a < 0;
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id select_type table partitions type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 pnull_pnullsp0,pnull_pnullsp1 ALL NULL NULL NULL NULL 2 Using where
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1 SIMPLE t1 pnull_pnullsp0,pnull_pnullsp1 ALL NULL NULL NULL NULL 6 Using where
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explain partitions select * from t1 where a <= 0;
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id select_type table partitions type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 pnull_pnullsp0,pnull_pnullsp1,p0_p0sp0,p0_p0sp1 ALL NULL NULL NULL NULL 4 Using where
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1 SIMPLE t1 pnull_pnullsp0,pnull_pnullsp1,p0_p0sp0,p0_p0sp1 ALL NULL NULL NULL NULL 6 Using where
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explain partitions select * from t1 where a > 1;
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id select_type table partitions type possible_keys key key_len ref rows Extra
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1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
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