doris Aggregate查询rollup explain 查询 使用expalin作为前缀可以查看当前sql语句的执行效率,以便于优化sql语句。explain的参数主要有十个分别为:id、select_type、table、type、possible_keys、key、key_len、ref、rows、Extra。 1. explain的作用: 例如: 1、id:id的值越大则代表越先执行。 2、select_type:常见的...
rollup函数使用sort耗时长,总耗时达到50s(即17号-20号算子的总耗时),(并行度32的情况下),20号算子Vector sort达24s,19号算子Vector Sore Aggregate达9s,18号算子做重分布达10s,17号算子hashagg达到8s。因此需要考虑对rollup类的分析函数考虑使用其它方式进行优化,比如用hashagg替代sortagg,避免大数据量排序性能降低。
the MySQL optimizer considers many techniques to efficiently performthe lookups involved in an SQL query. A query on a huge table can be performedwithout reading all the rows; a join involving several tables can be performedwithout comparing every combination of rows. The set of operations...
if (!ji || ji->created_functions == 0) return; /* calculate total time */ INSTR_TIME_SET_ZERO(total_time); INSTR_TIME_ADD(total_time, ji->generation_counter); INSTR_TIME_ADD(total_time, ji->inlining_counter); INSTR_TIME_ADD(total_time, ji->optimization_counter); INSTR_TIME_ADD(...
It can be an aggregate function or a combination of multiple aggregate functions. In SQL statements, aggregate operators are classified into the following types: GroupAggregate: Data has been pre-sorted based on the GROUP BY clause. HashAggregate: Data is hash-calculated, distributed to ...
AGGREGATION:Operators and steps used for queries that involve aggregate functions and GROUP BY operations. AggregateaggrOperator/step for scalar aggregate functions. HashAggregateaggrOperator/step for grouped aggregate functions. Can operate from disk by virtue of hash table spilling to disk. ...
In the previous articles I wrote about emulating some of the analytic functions inMySQL. Today, I'll write about four more userful functions:FIRST_VALUE,LAST_VALUE,LEADandLAG. These functions also do not have aggregate analogs. FIRST VALUE(column)returns the value of column from the first row...
One of the goals of SQL optimization is to push the calculation down to TiKV as much as possible. The Coprocessor in TiKV supports most of the built-in SQL functions (including the aggregate functions and the scalar functions), SQL LIMIT operations, index scans, and table scans. Operator inf...
SQL- Where Clause: Answer and Explanation: The purpose of ''Where'' clause in a query is to specify, to limit and to filter a condition when getting data from a table. Tables can be either be... Learn more about this topic:
we need to collect all the runtime statistics of the built inner child and aggregate them to only one result to present to the user. Contributor Author lysu commented Oct 12, 2018 yes~ if inner child is unqiue plan id (e.g. IndexLookUp_8), inner create multple times will share same...