Hologres兼容Postgres,可以根据EXPLAIN和EXPLAIN ANALYZE语法了解SQL的执行计划。 EXPLAIN:代表优化器QO根据SQL特征预估的SQL执行计划,并非实际的执行计划,对SQL的运行有一定参考意义。 EXPLAIN ANALYZE:代表SQL真实的运行计划,相比EXPLAIN会包含更多的实际运行信息,能准确的反映出SQL的执行算子和算子耗时,可以根据算子耗时去做...
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 ...
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...
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(...
Availability: availability means any client that requests data gets a response even if some of the nodes are down. Partition Tolerance: a partition indicates a communication break between two nodes. Partition tolerance means the system continues to operate despite network partitions. ...
(1) HashAggregate(keys=[k#47], functions=[partial_sum(cast(v#48 as bigint))], output=[k#47, sum#52L]) +- *(1) LocalTableScan [k#47, v#48] | +---+ -- Using Formatted EXPLAIN FORMATTED select k, sum(v) from values (1, 2), (1, 3) t(k, v) group by k; +---+...
(Storage Rows Scanned: 10000). Also, the data had to be sorted (viaSort Method: quicksort) on value (viaSort Key: value). You can improve this execution by modifying the above created index into a range index, so that you can avoid the sorting operation, and reduce the number of ...
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 that ...
functions, because, first, dealing with the concatenated string can be quite a tedious task for the groups with lots of records (large strings tend to overflow), and, second, the result depends on the order of the arguments (which is normally not the case for the aggregate functions). It...
QSM-02025 no aggregate functions Cause: The capability in question is not supported when the materialized view uses no aggregate functions. Action: Re-phrase the query to use aggregate functions. QSM-02026 non-AND conjunction in WHERE clause Cause: The capability in question is not supported ...