操作类型:全表扫描、索引扫描、连接操作(Hash Join/Sort Merge Join)等。 资源估算:各步骤的成本(Cost)、实际执行时间(Actual Time)。 数据流向:数据如何在节点间传输(如 Redistribute、Broadcast)。 2. GaussDB 特色优化 相较于传统数据库,GaussDB 在执行计划中增加了分布式特性标识: 数据分片策...
如果查询中使用到了内部的临时表,在执行计划的 Extra 列将会显示 Using temporary。上边的 GROUP BY 的执行计划的 Extra 列不仅仅包含 Using temporary 提示,还包含 Using filesort 提示,可是查询语句中明明没有写 ORDER BY 子句,这是因为 MySQL 会在包含 GROUP BY 子句的查询中默认添加上 ORDER BY 子句。 如果...
static void show_sort_info(SortState *sortstate, ExplainState *es);static void show_hash_info(HashState *hashstate, ExplainState *es);static void show_tidbitmap_info(BitmapHeapScanState *planstate, ExplainState *es);static void show_instrumentation_count(const char *qlabel, int which, Plan...
When query log structure is changed after system update, then old table will be renamed and new table will be created automatically. --> <database>system</database> query_log <!-- PARTITION BY expr https://clickhouse.yandex/docs/en/table_engines/custom_partitioning_key/ Example: event_date...
Example The queue data structure can be understood with the help of a queue at a bus stand. The person who reaches first at the bus stand is the first person in the queue and other persons stand him as they reach the bus stand. When the bus arrives, the person who reached first at ...
using the EXPLAIN statement creates the access plan by recompiling the statement. The resulting access plans from each of these two methods of creating access plans can be different. For example, if the statement in a section was compiled, say, 2 hours ago, then the acce...
Explain with an example how a two-dimensional array can be passed to a Method. Using JAVA, complete the following: 1. Describe a case where quicksort will resort in quadratic behavior. 2. Give a concise and accurate...
For example, if the scan is the outer of a nested loop join). 'FAST' indicates that the scan is expected to progress with higher speed. This information is used to group scans together for efficient sharing of bufferpool records. SPILLED INTEGER Estimated number of pages in SORT spill. ...
Can Struct stored in heap?! can VB & C# to be used in same project? Can we add derived class object to base class object? Can we change the return type of a method during overriding in c# Can we const with String.Format Can we create multiple sql connection object from multiple thr...
答案解析:[听力原文]1-10 It is common nowadays for companies and industries to sponsor big sports events. For example, many companies sponsored the 8th National Games held in Shanghai in 1997. Then, what exactly do companies and industries get out of sponsoring big sports events, such as inte...