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4cff562f3f
They were based on the maximum possible key tuple length, which can be much larger than the real data size. The return value is used by handler::keyread_time(), which is used to estimate the cost of range access. This could cause range access not to be picked, even if it uses the clustered PK and reads about 8% of the table. The fix is to add KEY::stat_storage_length (next to KEY::rec_per_key) and have the storage engine fill it in handler::info(HA_STATUS_CONST). Currently, only InnoDB fills this based on its internal statistics: index->stat_index_size and ib_table->stat_n_rows. Also changed: - In handler::calculate_costs(), use ha_keyread_clustered_time() when computing clustered PK read cost, not ha_keyread_time(). The fix is OFF by default and enabled by setting FIX_INDEX_LOOKUP_COST flag in @@new_mode.
60 lines
2 KiB
Text
60 lines
2 KiB
Text
SET @global_start_value = @@global.new_mode;
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SELECT @global_start_value;
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@global_start_value
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SET @session_start_value = @@session.new_mode;
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SELECT @session_start_value;
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@session_start_value
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SET @@global.new_mode = DEFAULT;
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SELECT @@global.new_mode;
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@@global.new_mode
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SELECT @@session.new_mode;
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@@session.new_mode
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SET @@session.new_mode = "TEST_WARNING1";
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Warnings:
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Warning 4200 The setting 'new_mode=TEST_WARNING1' is ignored. It only exists for compatibility with old installations and will be removed in a future release
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SET @@session.new_mode = "TEST_WARNING1,TEST_WARNING2";
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Warnings:
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Warning 4200 The setting 'new_mode=TEST_WARNING1' is ignored. It only exists for compatibility with old installations and will be removed in a future release
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Warning 4200 The setting 'new_mode=TEST_WARNING2' is ignored. It only exists for compatibility with old installations and will be removed in a future release
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SET @@session.new_mode = "TEST_WARNING1,TEST_WARNING2,TEST_WARNING3";
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ERROR 42000: Variable 'new_mode' can't be set to the value of 'TEST_WARNING3'
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SET @@session.new_mode = "ALL";
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select @@session.new_mode;
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@@session.new_mode
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FIX_INDEX_STATS_FOR_ALL_NULLS,FIX_INDEX_LOOKUP_COST
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SET @@global.new_mode = NULL;
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ERROR 42000: Variable 'new_mode' can't be set to the value of 'NULL'
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SET @@global.new_mode = '';
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SELECT @@global.new_mode;
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@@global.new_mode
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SET @@global.new_mode = ' ';
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SELECT @@global.new_mode;
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@@global.new_mode
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SET @@session.new_mode = NULL;
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ERROR 42000: Variable 'new_mode' can't be set to the value of 'NULL'
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SET @@session.new_mode = '';
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SELECT @@session.new_mode;
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@@session.new_mode
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SET @@session.new_mode = ' ';
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SELECT @@session.new_mode;
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@@session.new_mode
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SET @@global.new_mode = OFF;
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ERROR 42000: Variable 'new_mode' can't be set to the value of 'OFF'
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SET @@session.new_mode = OFF;
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ERROR 42000: Variable 'new_mode' can't be set to the value of 'OFF'
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SET @@global.new_mode = @global_start_value;
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SELECT @@global.new_mode;
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@@global.new_mode
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SET @@session.new_mode = @session_start_value;
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SELECT @@session.new_mode;
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@@session.new_mode
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