https://sourceforge.net/p/whitebear/allura-wiki/Use_of_statistical_data/Recent changes to Use_of_statistical_dataenTue, 27 May 2014 17:59:42 -0000https://sourceforge.net/p/whitebear/allura-wiki/Use_of_statistical_data/<div class="markdown_content"><pre>--- v1 +++ v2 @@ -1,3 +1,7 @@ **Statistical data** should be used by the relational engine in order to calculate operation cost. The following values could be got from statistical data: smallest and largest value, number of values and cardinality. Medium cardinality should be calculated this way: number of values / number of records (from table header) [Statistical_data] should be stored in index-like B+ tree structures. These structures should be read / written using the physical layer. Statistical data should contain cardinality (number of records) for every value stored in a given field. Statistical data should be created for every non-unique field (cardinality of values in a unique index is always 1). They should be updated when a record is updated, at the same time as records and indexes. + +## See also + +[Set_engine] </pre> </div>silex6Tue, 27 May 2014 17:59:42 -0000https://sourceforge.net1dc5f1069ddcb6fa30dd3fc05c106ce9b9e2f227https://sourceforge.net/p/whitebear/allura-wiki/Use_of_statistical_data/<div class="markdown_content"><p><strong>Statistical data</strong> should be used by the relational engine in order to calculate operation cost. The following values could be got from statistical data: smallest and largest value, number of values and cardinality. Medium cardinality should be calculated this way: number of values / number of records (from table header) </p> <p><span>[Statistical_data]</span> should be stored in index-like B+ tree structures. These structures should be read / written using the physical layer. Statistical data should contain cardinality (number of records) for every value stored in a given field. Statistical data should be created for every non-unique field (cardinality of values in a unique index is always 1). They should be updated when a record is updated, at the same time as records and indexes. </p></div>silex6Tue, 27 May 2014 17:59:42 -0000https://sourceforge.net7a48cb9dd4630e88329279e41012635a40ced32f