2026-03-12 21:01:38

histograms/histogram_07.txt

@@ -0,0 +1,48 @@
+exec dbms_stats.delete_table_stats('SYS','T1');
+
+
+exec dbms_stats.gather_table_stats(user,'T1', method_opt=>'for columns size 20 col1');
+
+exec dbms_stats.gather_table_stats(user,'T1', method_opt=>'for all columns size 1');
+
+
+
+
+set pages 50 lines 256
+
+alter system flush shared_pool;
+
+drop table Q purge;
+
+create table Q as
+   select /*+ GATHER_PLAN_STATISTICS */
+       a.COL1    COL1
+   from
+       T1 a,
+       T1 b
+   where
+     a.COL1=9999 and
+     a.COL1=b.COL1
+   /
+
+select * from table(dbms_xplan.display_cursor(null,null,'ALLSTATS LAST  +PEEKED_BINDS +PARALLEL +PARTITION +COST +BYTES'));
+
+
+
+density = (nr_of_lines/_distinct_values)/100 = frequency_of_column / 100
+
+
+
+frequency_of_non_popular_values = (nr_of_lines-sum(endpoint repeat count)) / (number_of_distinct_values - number_of_endpoints)
+
+
+
+ 32 LINES ---- 17 NON POP
+ ?               
+
+
+ Test: val popuaire
+ val non populaire
+ val non populaire out of range
+
+