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01c82173dd
The original code was there to favor index search over table scan. This is not needed anymore as the cost calculations for table scans and index lookups are now more exact.
153 lines
3.6 KiB
Plaintext
153 lines
3.6 KiB
Plaintext
set @save_use_stat_tables = @@use_stat_tables;
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set @@use_stat_tables = COMPLEMENTARY;
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CREATE TABLE test_ps_fetch
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(a INT, b INT, c INT, d INT, PRIMARY KEY (a, b), INDEX idx (c, d))
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ENGINE=INNODB STATS_PERSISTENT=1;
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ANALYZE TABLE test_ps_fetch;
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Table test.test_ps_fetch
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Op analyze
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Msg_type status
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Msg_text Engine-independent statistics collected
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Table test.test_ps_fetch
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Op analyze
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Msg_type status
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Msg_text OK
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SELECT n_rows, clustered_index_size, sum_of_other_index_sizes
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FROM mysql.innodb_table_stats WHERE table_name = 'test_ps_fetch';
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n_rows 0
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clustered_index_size 1
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sum_of_other_index_sizes 1
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SELECT index_name, stat_name, stat_value, sample_size, stat_description
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FROM mysql.innodb_index_stats WHERE table_name = 'test_ps_fetch'
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ORDER BY index_name, stat_name;
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index_name PRIMARY
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stat_name n_diff_pfx01
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stat_value 0
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sample_size 1
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stat_description a
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index_name PRIMARY
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stat_name n_diff_pfx02
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stat_value 0
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sample_size 1
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stat_description a,b
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index_name PRIMARY
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stat_name n_leaf_pages
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stat_value 1
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sample_size NULL
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stat_description Number of leaf pages in the index
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index_name PRIMARY
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stat_name size
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stat_value 1
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sample_size NULL
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stat_description Number of pages in the index
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index_name idx
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stat_name n_diff_pfx01
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stat_value 0
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sample_size 1
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stat_description c
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index_name idx
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stat_name n_diff_pfx02
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stat_value 0
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sample_size 1
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stat_description c,d
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index_name idx
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stat_name n_diff_pfx03
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stat_value 0
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sample_size 1
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stat_description c,d,a
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index_name idx
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stat_name n_diff_pfx04
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stat_value 0
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sample_size 1
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stat_description c,d,a,b
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index_name idx
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stat_name n_leaf_pages
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stat_value 1
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sample_size NULL
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stat_description Number of leaf pages in the index
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index_name idx
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stat_name size
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stat_value 1
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sample_size NULL
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stat_description Number of pages in the index
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SELECT index_name, seq_in_index, column_name, cardinality
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FROM information_schema.statistics WHERE table_name = 'test_ps_fetch'
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ORDER BY index_name, seq_in_index;
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index_name idx
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seq_in_index 1
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column_name c
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cardinality 0
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index_name idx
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seq_in_index 2
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column_name d
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cardinality 0
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index_name PRIMARY
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seq_in_index 1
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column_name a
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cardinality 0
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index_name PRIMARY
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seq_in_index 2
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column_name b
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cardinality 0
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SELECT
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table_rows, avg_row_length, max_data_length, index_length
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FROM information_schema.tables WHERE table_name = 'test_ps_fetch';
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table_rows 0
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avg_row_length 0
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max_data_length 0
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index_length 16384
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UPDATE mysql.innodb_table_stats SET
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n_rows = 1000,
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clustered_index_size = 5
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WHERE
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table_name = 'test_ps_fetch';
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UPDATE mysql.innodb_index_stats SET
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stat_value = 20
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WHERE
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table_name = 'test_ps_fetch' AND
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index_name = 'PRIMARY' AND
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stat_name = 'n_diff_pfx01';
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UPDATE mysql.innodb_index_stats SET
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stat_value = 90
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WHERE
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table_name = 'test_ps_fetch' AND
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index_name = 'PRIMARY' AND
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stat_name = 'n_diff_pfx02';
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UPDATE mysql.innodb_index_stats SET
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stat_value = 3
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WHERE
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table_name = 'test_ps_fetch' AND
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index_name = 'idx' AND
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stat_name = 'n_diff_pfx01';
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UPDATE mysql.innodb_index_stats SET
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stat_value = 11
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WHERE
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table_name = 'test_ps_fetch' AND
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index_name = 'idx' AND
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stat_name = 'n_diff_pfx02';
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FLUSH TABLE test_ps_fetch;
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SELECT seq_in_index, column_name, cardinality
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FROM information_schema.statistics WHERE table_name = 'test_ps_fetch'
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ORDER BY index_name, seq_in_index;
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seq_in_index 1
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column_name c
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cardinality 3
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seq_in_index 2
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column_name d
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cardinality 11
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seq_in_index 1
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column_name a
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cardinality 20
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seq_in_index 2
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column_name b
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cardinality 90
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SELECT
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table_rows, avg_row_length, max_data_length, index_length
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FROM information_schema.tables WHERE table_name = 'test_ps_fetch';
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table_rows 1000
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avg_row_length 81
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max_data_length 0
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index_length 16384
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DROP TABLE test_ps_fetch;
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set @@use_stat_tables = @save_use_stat_tables;
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