当一条SQL语句发生全表扫描、全分区扫描及索引快速全扫描的时候,若优化器满足下面的条件之一就可以使用并行处理: ① 会话级别,会话设置了强制并行,例如,“ALTER SESSION FORCE PARALLEL QUERY PARALLEL 4;”,执行“SELECT COUNT(*) FROM TB_PART_LHR;”,这里的TB_PART_LHR为分区表。 ② 语句级别,SQL语句中有Hin...
Select /*+parallel(tab n)*/ from tab; Alter session force parallel query parallel n; 如果没有设置将执行默认并行度 3. 默认并行度 单实例 = PARALLEL_THREADS_PER_CPU x CPU_COUNT RAC = PARALLEL_THREADS_PER_CPU x CPU_COUNT x INSTANCE_COUNT SQL> show parameter parallel NAME TYPE VALUE --- ...
Select /*+parallel(tab n)*/ from tab; Alter session force parallel query parallel n; 如果没有设置将执行默认并行度 3. 默认并行度 单实例 = PARALLEL_THREADS_PER_CPU x CPU_COUNT RAC = PARALLEL_THREADS_PER_CPU x CPU_COUNT x INSTANCE_COUNT SQL> show parameter parallel NAME TYPE VALUE --- ...
no parallel plan is generated. For example, a cursor created using DECLARE CURSOR will never use a parallel plan. Similarly, a PL/pgSQL loop of the form FOR x IN query LOOP … END LOOP will never use a parallel plan, because the parallel...
Alter session force parallel query parallel n; 如果没有设置将执行默认并行度 3. 默认并行度 单实例 = PARALLEL_THREADS_PER_CPU x CPU_COUNT RAC = PARALLEL_THREADS_PER_CPU x CPU_COUNT x INSTANCE_COUNT SQL> show parameter parallel NAME TYPE VALUE ...
The PostgreSQL documentation has achapter on the limitations of parallel query. For example, most data modifying statements don't support parallel query. Also, queries that usePARALLEL UNSAFEfunctions or are executed in a cursor cannot use parallel query. But none of these limitations can affect us...
Certain operators can cause a section of the query plan to run in serial mode, or the whole plan to run in serial mode. See Also Reference sp_configure (Transact-SQL) Query Hints (Transact-SQL) Concepts Degree of Parallelism Parallel Query Example Parallel Index Operations max degree ...
For information about how to interpret EXPLAIN output for a parallel query and the parts of SQL statements that parallel query can apply to, see SQL constructs for parallel query in Aurora MySQL. The following example output shows the results of running the preceding query on a db.r4.2xlar...
"Parallel Query Indexing"in theOracle Secure Enterprise Search Administrator's Guide. Parallel Query Example This example creates two partitions, using the default OES storage area and a newly created OES1 storage area: Usingsearchadmin, export the XML description of the default OES storage area to...
Using Transact-SQL To set max degree of parallelism on an existing index In Object Explorer, connect to an instance of Database Engine. On the Standard bar, click New Query. Copy and paste the following example into the query window and click Execute. SQL Copy USE AdventureWorks2022; GO ...