Oracle中关于bitmap index的使用问题 您如果熟悉Oracle数据库,我想您对 Thomas Kyte 的大名一定不会陌生。 Tomas 主持的 asktom.oracle.com 网站享誉 Oracle 界数十年,绝非幸致。最近在图书馆借到这位 Oracle 绝顶高手编著的《 Expert Oracle Database Architecture-9i
EXECUTE immediate 'analyze index i_easy1 COMPUTE STATISTICS'; SELECT lEAF_BLOCKS INTO v_bt_sp FROM user_indexes where index_name='I_EASY1'; EXECUTE immediate 'analyze index i_easy2 COMPUTE STATISTICS'; SELECT LEAF_BLOCKS INTO v_bm_sp FROM user_indexes where index_name='I_EASY2'; INSERT...
可以发现,相比于没有建立 Index 的逐行扫描情况,使用 Bitmap 进行索引的操作时间复杂度近乎为 O(1) (仅仅将两张 Bitmap 进行了一次‘与’操作),因此显著增加了查询的效率,降低了获取结果所需的时间。 Bitmap 的适用场景 低基数情况 (Low cardinality columns) 当所需查询的 Column 仅具备少量不同值 (e.g. ...
In the above table, culumn EMPNO has 100-percent distinct values and is a good candidate to become a primary key. If you define this culumn as a primary key, you will create a B-tree index and not a bitmap index because Oracle does not support bitmap primary key indexes. ...
Restrictions on Bitmap Join IndexesIn addition to the restrictions on bitmap indexes in general (seeBITMAP), the following restrictions apply to bitmap join indexes: You cannot create a bitmap join index on an index-organized table or a temporary table. ...
A method and apparatus for segmenting bitmaps in a bitmap index is provided. A segmented bitmap includes a plurality of bitmap segments that are used to indicate which records in a body of records that is associated with the segmented bitmap satisfy a particular criteria. Each bitmap segment...
repeatedly with each stored rowid. In a bitmap index, a bitmap for each key value is used instead of a list of rowids. 索引的目的是提供指针指向一个表中的行,行包含了一个被给定的主键值。在常规索引中, 它的完成是通过存储ROWID的列表对于每个主键对应的行和它主键值。ORACLE存储每个主键 ...
B+树索引 B+树索引适合全键值、键值范围、键前缀查找 跟oracle的b+数是一个结构。 聚簇索引的叶节点存储数据页,其结构是一致的。 哈希索引 哈希索引基于哈希表实现,只有精确匹配索引所有列的...hash索引,仅支持 Adaptive Hash Index Adaptive Hash Index InnoDB存储引擎会监控对表上索引的查找,如果观察到建立哈希...
Oracle recommends that you enable automatic sizing of SQL working areas by setting PGA_AGGREGATE_TARGET instead. CREATE_BITMAP_AREA_SIZE is retained for backward compatibility. A larger value may speed up index creation. Cardinality is the number of unique values in a column in relation to the...
All, I have a question in bitmap index. It would be great if any one could clarify this... I have two scenario's. In first scenario, it is locking. But the second scenario, it is not locking. I am not sure why it is... Scenario 1 === Sessi