原文链接:Optimizing Queries Using Materialized Views:A Practical, Scalable Solution 该论文提出SPJG查询改写,高效实现基于selection, project, join, group-by算子匹配的视图改写方案,是当前很多计算引擎的物化视图查询改写的理论基础,例如:Calcite、Doris、StarR
Optimizing the Execution Order between Analytical Functions and Joins in SQL QueriesExecution of a query invoking an analytical function (AF) is optimized. The query includes a join operation between an AF table and an AuxiliaryTable and includes determining that the AF includes a plurality of AF ...
Because eachInnoDBtable has aprimary key(whether you request one or not), specify a set of primary key columns for each table, columns that are used in the most important and time-critical queries. Do not specify too many or too long columns in the primary key, because these column values...
type:查询所使用的类型 type:查询使用了何种类型,它在SQL优化中是一个非常重要的指标,以下性能从好到坏依次是:system>const>eq_ref>ref>ref_or_null>index_merge>unique_subquery>index_subquery>range > index> ALL 除了all之外,其他的type都可以使用到索引,除了index_merge之外,其他的type只可以用到一个索引 A...
如上SQL,由于单表谓词在parititon key上,在优化期间即可确定哪些可以分区可以避免访问,即静态pruning。 上例中的数据也可以改写为star schema的形态: SELECT avg(amount)FROM ordersWHERE date id IN(SELECT date idFROM date_dimWHERE year = 2013 ANDmonth BETWEEN 10 AND 12); ...
MySQL retrieves the latest statistics from the storage engine and caches them in the mysql.index_stats and mysql.table_stats dictionary tables. Subsequent【ˈsʌbsɪkwənt随后的;之后的;后来的;接后的;】 queries retrieve the cached statistics until the cached statistics expire. A server res...
There are pairs of tables that meet the criteria for maintaining correlation statistics, but queries that join these tables do not specify a date restriction in their predicates. To set the DATE_CORRELATION_OPTIMIZATION database option ALTER DATABASE (Transact-SQL) Working with Correlation Statistics...
outer_exprIN(SELECTinner_exprFROM...WHEREsubquery_where) MySQL evaluates queries“from outside to inside.”That is, it first obtains the value of the outer expressionouter_expr, and then runs the subquery and captures the rows that it produces. ...
如上SQL,由于单表谓词在parititon key上,在优化期间即可确定哪些可以分区可以避免访问,即静态pruning。 上例中的数据也可以改写为star schema的形态: SELECT avg(amount) FROM orders WHERE date id IN (SELECT date id FROM date_dim WHERE year = 2013 AND month BETWEEN 10 AND 12); 这时Orders的值将需要...
The optimizer minimizes differences in handling of views and derived tables. This affects queries that use the STRAIGHT_JOIN modifier and a view with an IN subquery that can be converted to a semijoin. The following query illustrates this because the change in processing causes a change in trans...