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、StarRocks都基于优化器的SPJG结构改写进行扩展实现。 该论文主要...
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 ...
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...
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); 这时Orders的值将需要根据date_...
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...
Queries that access large amounts of data (typical data warehouse queries) often can be parallelized. This is extremely useful for reducing the response time in low concurrency data warehouse. However, for OLTP environments, which tend to be high concurrency, this can adversely impact other users...
>>Optimizing Database Queries When it comes to understanding a how a query is resolved there is nothing better than using the ‘Show Execution Plan’ feature of SQL Query analyzer. I am certain you are aware that using OR operators in a SQL where clause can be potentially devastating to ...
8.2.2 Optimizing Subqueries, Derived Tables, and View References 8.2.3 Optimizing INFORMATION_SCHEMA Queries 8.2.4 Optimizing Data Change Statements 8.2.5 Optimizing Database Privileges 8.2.6 Other Optimization Tips The core logic of a database application is performed through SQL statements, whether ...
Sergei, indeed: in cases where it matters, such as in mk-table-checksum, I run test queries to find out which place the “real” expression needs to go and where the user variables can be substituted. The result is often that the real expression goes LAST, not first! It looks odd but...