101 lines
3.8 KiB
Plaintext
101 lines
3.8 KiB
Plaintext
select OBJECT_INSTANCE_BEGIN, NAME from performance_schema.rwlock_instances
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limit 1
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into @oib, @name;
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select WRITE_LOCKED_BY_THREAD_ID from performance_schema.rwlock_instances
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where WRITE_LOCKED_BY_THREAD_ID is not NULL
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limit 1
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into @wlbtid;
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Warnings:
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Warning 1329 No data - zero rows fetched, selected, or processed
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====================================================================
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Testing index for columns OBJECT_INSTANCE_BEGIN
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====================================================================
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############ Explain for Query ####################################
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explain select READ_LOCKED_BY_COUNT
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from performance_schema.rwlock_instances
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where OBJECT_INSTANCE_BEGIN = "impossible";
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id select_type table partitions type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE NULL NULL NULL NULL NULL NULL NULL # NULL no matching row in const table
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############ Explain for Query ####################################
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explain select READ_LOCKED_BY_COUNT
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from performance_schema.rwlock_instances
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where OBJECT_INSTANCE_BEGIN > "impossible";
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id select_type table partitions type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE rwlock_instances NULL ALL PRIMARY NULL NULL NULL # 33.33 Using where
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############ Explain for Query ####################################
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explain select READ_LOCKED_BY_COUNT
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from performance_schema.rwlock_instances
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where OBJECT_INSTANCE_BEGIN < "2";
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id select_type table partitions type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE rwlock_instances NULL ALL PRIMARY NULL NULL NULL # 33.33 Using where
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############ Explain for Query ####################################
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explain select READ_LOCKED_BY_COUNT
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from performance_schema.rwlock_instances
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where OBJECT_INSTANCE_BEGIN = @oib;
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id select_type table partitions type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE rwlock_instances NULL const PRIMARY PRIMARY 8 const # 100.00 NULL
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############# Explain End #########################################
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flush status;
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select READ_LOCKED_BY_COUNT
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from performance_schema.rwlock_instances
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where OBJECT_INSTANCE_BEGIN = @oib;
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READ_LOCKED_BY_COUNT
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#
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OK: handler_read_key incremented
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====================================================================
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Testing index for columns NAME
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====================================================================
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############ Explain for Query ####################################
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explain select READ_LOCKED_BY_COUNT
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from performance_schema.rwlock_instances
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where NAME = "impossible";
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id select_type table partitions type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE rwlock_instances NULL ref NAME NAME 514 const # 100.00 NULL
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############ Explain for Query ####################################
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explain select READ_LOCKED_BY_COUNT
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from performance_schema.rwlock_instances
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where NAME > "impossible";
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id select_type table partitions type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE rwlock_instances NULL ALL NAME NULL NULL NULL # 33.33 Using where
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############ Explain for Query ####################################
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explain select READ_LOCKED_BY_COUNT
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from performance_schema.rwlock_instances
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where NAME < "2";
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id select_type table partitions type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE rwlock_instances NULL ALL NAME NULL NULL NULL # 33.33 Using where
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############ Explain for Query ####################################
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explain select READ_LOCKED_BY_COUNT
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from performance_schema.rwlock_instances
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where NAME = @name;
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id select_type table partitions type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE rwlock_instances NULL ref NAME NAME 514 const # 100.00 NULL
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############# Explain End #########################################
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flush status;
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select READ_LOCKED_BY_COUNT
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from performance_schema.rwlock_instances
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where NAME = @name;
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READ_LOCKED_BY_COUNT
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OK: handler_read_key incremented
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