CREATE[UNIQUE]INDEX[CONCURRENTLY][[IFNOTEXISTS]name]ON[ONLY]table_name[USINGmethod]({column_name|(expression)}[COLLATEcollation][opclass[(opclass_parameter=value[,...])]][ASC|DESC][NULLS{FIRST|LAST}][,...])[INCLUDE(column_name[,...])][WITH(storage_parameter[=value][,...])][TABLESP...
1、创建:创建虚拟索引,create index 索引名 on 表名(列名) nosegment使用 explain plan for 查看是否会用到索引explain plan for 查询语句select * from table( dbms_xplan.display());2、优势:用于预判待加入的索引是否能起作用 3、特点: (1)虚拟索引无法执行alter index选项 SQL> alter index idx_wxw rebuil...
CREATE [UNIQUE] | [BITMAP] INDEX index_name ON table_name ([column1 [ASC|DESC],column2[ASC|DESC],...] | [express]) [TABLESPACE tablespace_name] [PCTFREE n1] [STORAGE (INITIAL n2)] [NOLOGGING] [NOLINE] [NOSORT]; 1. 2. 3. 4. 5. 6. 7. 8. 这些参数的含义如下: - UNIQUE:...
order by stddev_time desc limit 5; (4)最耗共享内存的SQL select userid::regrole, dbid, query from pg_stat_statements order by (shared_blks_hit+shared_blks_dirtied) desc limit 5; (5)最耗临时空间的SQL select userid::regrole, dbid, query from pg_stat_statements order by temp_blks_wri...
postgres=#createindexidx_tbl_log_1ontbl_log (gid,crt_timedesc);CREATEINDEXTime:3530.425ms (00:03.530) 重新查询后, 使用了索引, 但是性能并没有提升多少. 避免了外部排序, 但是依旧有大量的扫描(shared hit=16266 read=517194 written=8941, 耗时2736.351毫秒). ...
CreateQueryDesc:给执行器创建执行描述符 _SPI_pquery:DML使用Executor执行查询 ExecutorStart ExecutorRun ExecutorFinish ExecutorEnd 代码语言:javascript 复制 res=_SPI_execute_plan(&plan,&options,InvalidSnapshot,InvalidSnapshot,true);_SPI_end_call(true);returnres;}...
CREATE INDEX test2_info_nulls_low ON test2(info NULLS FIRST);CREATE INDEX test3_desc_index ON test3(id DESC NULLS LAST); 2、Hash索引 散列(Hash)索引只能处理简单的等于比较 当索引列使用等于操作符进行比较时,查询规划器会考虑使用散列索引
CREATE INDEX test2_info_nulls_low ON test2 (info NULLS FIRST); CREATE INDEX test3_desc_index ON test3 (id DESC NULLS LAST); 0 2、Hash索引 散列(Hash)索引只能处理简单的等于比较 当索引列使用等于操作符进行比较时,查询规划器会考虑使用散列索引 PostgreSQL散列索引的性能不比B-Tree索引强,但是散列索...
crosstab \errverbose show most recent error message at maximum verbosity \g [(OPTIONS)] [FILE] execute query (and send result to file or |pipe); \g with no arguments is equivalent to a semicolon \gdesc describe result of query, without executing it \gexec execute que...
create index idx_persons_age_desc on persons (age desc nulls last); 重新编制索引 过了一段时间,索引可能会变得过时,可能需要重建。Postgres提供了一个reindex命令来完成这个任务,但由于在这个过程中Postgres会对索引放置锁,您可能希望使用concurrent关键字。 reindex index concurrently idx_persons_age; 或者您可以...