如果你说的是set的cardinality，那么cardinality就是集合中元素的个数。那么，你可能会问：直接叫count不...
Cardinality’s official, non-database dictionary definition is mathematical: the number of values in a set. When applied to databases, the meaning is a bit different: it’sthe number of distinct values in a table column relative to the number of rows in the table. Repeated values in the c...
The bigger the table, the larger the data size - at a certain point, the saving in the dictionary no longer replaces the saving in data size. There is a point where the optimization is actually worsening the situation also in data size. It seems you are at the sweet point, mean...
Cardinality estimation (CE) in SQL Server is derived primarily from histograms that are created when indexes or statistics are created, either manually or automatically. Sometimes, SQL Server also uses constraint information and logical rewrites of queries to determine cardinality...
Subsequent updates started with SQL Server 2014 (12.x), meaning compatibility levels 120 and above. The CE updates for levels 120 and above incorporate updated assumptions and algorithms that work well on modern data warehousing and on OLTP workloads. From the CE 70 assumptions, the following ...
* This code executes registered procedures stored in the * operator relation, by calling the function manager. * * See clause_selectivity() for the meaning of the additional parameters. */Selectivityrestriction_selectivity(PlannerInfo *root,
Cardinality estimation in SQL Server is derived primarily from histograms created when indexes or statistics are created, either manually or automatically. Sometimes, SQL Server also uses constraint information and logical rewrites of queries to determine cardinality....
The present disclosure is related to databases, and in particular, to cardinality estimation in databases. BACKGROUND When a query statement such as an SQL (structured query language) query statement is received from a client by a database, steps such as syntax analysis, semantic analysis, and ...
“Overall, the introduction of InfluxDB 3.0 represents the beginning of a new chapter for the InfluxDB platform, giving users the ability to create time series on the fly from raw, high-precision data, meaning it powers expanded use cases across observability, real-...
/// Adds a tag to be included in any metric or Sentry error emitted from this point in the /// request lifecycle onwards. Tags **must** have low cardinality, meaning that the number of /// distinct possible values associated with a given tag must be small. fn add_tag(&self, key:...