Will oracle cardinality affect query speed?

The cardinality will affect the optimizer's evaluation of the cost. The simplest example is a query:

select * from test where id=1 and sex='male';

There are separate indexes on both the id and sex fields, and the cardinality of the id column is large and the cardinality of the sex column is small, so the database will give priority to the index on the id column when evaluating the execution plan.The cardinality of the id column is large and the selectivity is good, so the amount of io is small when scanning.The final estimated cost is small.

The cardinality will affect the optimizer's evaluation of the cost. The simplest example is a query:

select * from test where id=1 and sex='male';

There are separate indexes on both the id and sex fields, and the cardinality of the id column is large and the cardinality of the sex column is small, so the database will give priority to the index on the id column when evaluating the execution plan.The cardinality of the id column is large and the selectivity is good, so the amount of io is small when scanning.The final estimated cost is small.

I don't think so, but using bitmap indexes on fields with small cardinality can improve query speed

Standard indexes are implemented by storing sorted index columns and corresponding ROWIDs in the index.If we build a standard index on a column with a small cardinality, it will return a large number of records.

When we create a bitmap index, Oracle will scan the entire table and create a bitmap for each value of the index column.If the content is the same, it will be represented by the same number on the bitmap.At this time, if the cardinality of this field is relatively small, the efficiency will be very high if you need to query the entire field.Because at this time, the database only needs to find out the content with the same number in the bitmap.

Cardinality The number of unique keys (Distinct_keys) in a column. For example, if there is a table with 100W rows, the cardinality of the gender column is 2 (select distinct gender from test), the cardinality of the primary key column is 100W(select distinct mid from test);Selectivity cardinality/percentage of total rows, gender 2/100w * 100% primary key 100%, the higher the selectivity, the better the use of the index 20~30% even if it is relatively high 1, how to judge whether an index is created is goodOr is it bad?It depends on his cardinality and selectivity. If the cardinality is large and the selectivity is large, it is better to use an index.

The change of cardinality affects the selectivity of the index and will definitely affect the query speed.
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The speed is not directly related to the full table size.It is related to whether to use an index or not, and to return the number of rows.If it is a primary key query, 10 billion is no problem.I used to have a single table of 10 billion, and the performance was good.Not only primary key queries, but also range queries.