Oracle In_memory查询中包含非in_memory列能否使用In_memory
查询中包含非in_memory列,则不能使用in_memory。
官方文档摘录如下:
Queries That Reference NO INMEMORY Columns
When a query references a NO INMEMORY
column, the table scan retrieves data from the row store rather than the IMCUs in the IM column store. Row store access occurs even if all other columns referenced in the query are populated INMEMORY
columns.
For example, assume that the customers
table is populated into the IM column store. The cust_id
and cust_last_name
columns are specified INMEMORY
, but the cust_postal_code
column is specified as NO INMEMORY
. You issue the following query:
SELECT cust_id, cust_last_name, cust_postal_code
FROM customers
WHERE cust_id < 5001
ORDER BY cust_id;
In this case, the database accesses the row store, not the IM column store, even though cust_postal_code
is the only NO INMEMORY
column referenced in the query. The following query, which has cust_postal_code
in the predicate but not the SELECT
list, must also access the row store:
SELECT cust_id, cust_last_name
FROM customers
WHERE cust_postal_code = 77501
ORDER BY cust_id;
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