Oracle's index mainly contains two categories: btree and bitmap indexes. By default, most of the BTree index is usually used, which is usually the only index, clustered index, and more, BTREE is used in OLTP, speed up the query speed. The bitmap index is a more compelling place for Oracle, which is mainly used in OLAP (online data analysis), which is used in data warehouses, and the purpose is to speed up the query speed is saved. Under normal circumstances, the index has a relatively large storage space, and the bitmap uses the compression technology to achieve the disk space reduction. BTREE is used at the high group (ie, the data is different), and the bitmap is used in the low base number. The basic principle of bitmap index is to use bitmaps in the index instead of column values. Usually there is a very low set between the fact table and the dimension of the storm, use the bitmap index, more efficient, compared with the B * Tree index, only less storage space, so every Sub-reading can read more records, and compared to the B * Tree index, bitmap index will compare, connect, and aggregate become bit arithmetic operations, which greatly reduces runtime, which is great to get performance. Lifting. How to use the bitmap index in Oracle? The following matters should be considered. * If you want to use the bitmap index, the initialization parameter star_transformation_enable should be set to true. * Optimization mode should be CBO. For data warehouses, you should always consider using CBO (COST-based Optimizer). * Bitchart index should be built on the outer key column of every fact table. (This is just a general rule.) In addition, it is also a problem for how Cardinality in the data sheet is also a problem. Only 3 values containing only 3 values in 10,000 data is low, then 100 million records include 30,000 records is not low? For such a situation, it is recommended that a few data simulation tests. In general, in the data warehouse environment, the performance of the bitmap index is better than the B * Tree index. Also pay attention to the bitmap index is not designed for the OLTP database, and should not use a lot of use in the OLTP database, especially for those with updated operations. Oracle's index mainly contains two categories: btree and bitmap indexes. By default, most of the BTree index is usually used, which is usually the only index, clustered index, and more, BTREE is used in OLTP, speed up the query speed. The bitmap index is a more compelling place for Oracle, which is mainly used in OLAP (online data analysis), which is used in data warehouses, and the purpose is to speed up the query speed is saved. Under normal circumstances, the index has a relatively large storage space, and the bitmap uses the compression technology to achieve the disk space reduction. BTREE is used at the high group (ie, the data is different), and the bitmap is used in the low base number. The basic principle of bitmap index is to use bitmaps in the index instead of column values. Usually there is a very low set between the fact table and the dimension of the storm, use the bitmap index, more efficient, compared with the B * Tree index, only less storage space, so every Sub-reading can read more records, and compared to the B * Tree index, bitmap index will compare, connect, and aggregate become bit arithmetic operations, which greatly reduces runtime, which is great to get performance. Lifting. How to use the bitmap index in Oracle? The following matters should be considered.
* If you want to use the bitmap index, the initialization parameter star_transformation_enable should be set to true. * Optimization mode should be CBO. For data warehouses, you should always consider using CBO (COST-based Optimizer). * Bitchart index should be built on the outer key column of every fact table. (This is just a general rule.) In addition, it is also a problem for how Cardinality in the data sheet is also a problem. Only 3 values containing only 3 values in 10,000 data is low, then 100 million records include 30,000 records is not low? For such a situation, it is recommended that a few data simulation tests. In general, in the data warehouse environment, the performance of the bitmap index is better than the B * Tree index. Also pay attention to the bitmap index is not designed for the OLTP database, and should not use a lot of use in the OLTP database, especially for those with updated operations. Oracle's index mainly contains two categories: btree and bitmap indexes. By default, most of the BTree index is usually used, which is usually the only index, clustered index, and more, BTREE is used in OLTP, speed up the query speed. The bitmap index is a more compelling place for Oracle, which is mainly used in OLAP (online data analysis), which is used in data warehouses, and the purpose is to speed up the query speed is saved. Under normal circumstances, the index has a relatively large storage space, and the bitmap uses the compression technology to achieve the disk space reduction. BTREE is used at the high group (ie, the data is different), and the bitmap is used in the low base number. The basic principle of bitmap index is to use bitmaps in the index instead of column values. Usually there is a very low set between the fact table and the dimension of the storm, use the bitmap index, more efficient, compared with the B * Tree index, only less storage space, so every Sub-reading can read more records, and compared to the B * Tree index, bitmap index will compare, connect, and aggregate become bit arithmetic operations, which greatly reduces runtime, which is great to get performance. Lifting. How to use the bitmap index in Oracle? The following matters should be considered. * If you want to use the bitmap index, the initialization parameter star_transformation_enable should be set to true. * Optimization mode should be CBO. For data warehouses, you should always consider using CBO (COST-based Optimizer). * Bitchart index should be built on the outer key column of every fact table. (This is just a general rule.) In addition, it is also a problem for how Cardinality in the data sheet is also a problem. Only 3 values containing only 3 values in 10,000 data is low, then 100 million records include 30,000 records is not low? For such a situation, it is recommended that a few data simulation tests. In general, in the data warehouse environment, the performance of the bitmap index is better than the B * Tree index. Also pay attention to the bitmap index is not designed for the OLTP database, and should not use a lot of use in the OLTP database, especially for those with updated operations. Oracle's index mainly contains two categories: btree and bitmap indexes.
