48 lines
925 B
Plaintext
48 lines
925 B
Plaintext
exec dbms_stats.delete_table_stats('SYS','T1');
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exec dbms_stats.gather_table_stats(user,'T1', method_opt=>'for columns size 20 col1');
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exec dbms_stats.gather_table_stats(user,'T1', method_opt=>'for all columns size 1');
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set pages 50 lines 256
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alter system flush shared_pool;
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drop table Q purge;
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create table Q as
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select /*+ GATHER_PLAN_STATISTICS */
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a.COL1 COL1
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from
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T1 a,
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T1 b
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where
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a.COL1=9999 and
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a.COL1=b.COL1
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/
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select * from table(dbms_xplan.display_cursor(null,null,'ALLSTATS LAST +PEEKED_BINDS +PARALLEL +PARTITION +COST +BYTES'));
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density = (nr_of_lines/_distinct_values)/100 = frequency_of_column / 100
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frequency_of_non_popular_values = (nr_of_lines-sum(endpoint repeat count)) / (number_of_distinct_values - number_of_endpoints)
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32 LINES ---- 17 NON POP
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?
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Test: val popuaire
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val non populaire
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val non populaire out of range
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