Answer:Oracle index hint syntax is tricky because of the index hint syntax is incorrect it is treated as a comment and not implemented. Here is an example of the correct syntax for an index hint: select /*+ index(customer cust_primary_key_idx) */ * from customer; Also note that of yo...
HASH_AJThe HASH_AJ hint transforms a NOT IN subquery into a hash anti-join to access the specified table. The syntax of the HASH_AJ hint is HASH_AJ(table) where table specifies the name or alias of the table to be accessed.(depricated in Oracle 10g) INDEXThe INDEX hint explicitly c...
INDEXThe INDEX hint explicitly chooses an index scan for the specified table. The syntax of the INDEX hint is INDEX(table index) where:table specifies the name or alias of the table associated with the index to be scanned and index specifies an index on which an index scan is to be perfo...
Syntax:BATCH_TABLE_ACCESS_BY_ROWID ( [ @ queryblock ] tablespec [ tablespec ]... ) Description: The BATCH_TABLE_ACCESS_BY_ROWID hint instructs the optimizer to retrieve a few rowids from the index, then access the rows in data block order, to reduce accessing data block times . SQL?
此hint使CBO通过把指定表格作为内部表格的方式 拒绝hash joins把每个指定表格加入到另一原始行 例:SELECT /*+ NO_USE_HASH ( employees dept ) */ no_index_ffs 此hint使CBO拒绝对指定表格的指定标签进行fast full index scan Syntax: /*+ NO_INDEX_FFS ( tablespecindexspec ) */ lishixinzhi/...
在product表上name字段创建索引my_index，由于product表中数据量过低，所以默认执行计划是全表扫描（Seq Scan）。通过HINT操作，强制执行计划进行索引扫描。postgres=# CREATE INDEX my_index ON product USING btree (name) TABLESPACE pg_default;CREATE INDEXpostgres=# explain select name from product; Seq Scan ...
Syntax: /*+ NO_INDEX_FFS ( tablespecindexspec ) */ 在SQL优化过程中常见HINT的用法(前10个比较常用,前3个最常用): 1. /*+ INDEX */和/*+ INDEX(TABLE INDEX1, index2) */和/*+ INDEX(tab1.col1 tab2.col2) */和/*+ NO_INDEX */和/*+ NO_INDEX(TABLE INDEX1, index2) */ 表明对...
3) hint是下面介绍的具体提示之一,如果包含多个提示,则每个提示之间需要用一个或多个空格隔开。 4) text 是其它说明hint的注释性文本 5)使用表别名。如果在查询中指定了表别名,那么提示必须也使用表别名。例如:select /*+ index(e,dept_idx) */ * from emp e; ...
<1>/*+ALL_ROWS*/ 表明对语句块选择基于开销的优化方法,并获得最佳吞吐量,使资源消耗最小化. 例如: SELECT/*+ALL+_ROWS*/EMP_NO,EMP_NAM,DAT_INFROMBSEMPMSWHEREEMP_NO=“CCBZZP“; <2>./*+FIRST_ROWS*/ 表明对语句块选择基于开销的优化方法,并获得最佳响应时间,使资源消耗最小化. 例如:...
在带有 pg_hint_plan 的 PostgreSQL 中,您可以将其转换为: /*+IndexScan(table1 idx_table1_col)*/SELECTcol1,col2FROMtable1WHEREcol1='something'ORDERBYcol2LIMIT1; 连接操作提示 加入顺序提示 并行/并行度提示 pg_hint_plan中的示例用法,将并行工作者从默认值 2(max_parallel_workers_per_gather)增加到...