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What is filter and access in explain plan?
Access means we are using something to “access” the data – we only “access” relevant data. Filter means we are getting more data then we need, and we filter it after we get it. The filter will be applied to all rows and only those that pass the filter get sent along.
What is filter predicate?
The access predicates express the start and stop conditions of the leaf node traversal. Index filter predicate (“filter” for index operations) Index filter predicates are applied during the leaf node traversal only. They do not contribute to the start and stop conditions and do not narrow the scanned range.
What is filter predicate Oracle?
Filter” predicates are those that are applied to the rows returned from the index; they determine which rows are ultimately sent up to the next step in the query execution plan.
What is an Oracle predicate?
From Oracle FAQ. A predicate is the syntax used to specify a subset of rows to be returned. Predicates are specified in the WHERE clause of a SQL statement.
What is the difference between a predicate integer and an IntPredicate?
Java IntPredicate interface is a predicate of one int-valued argument. It can be considered an operator or function that returns a value either true or false based on certain evaluation on the argument int value. IntPredicate is a functional interface whose functional method is boolean test(int a) .
How are access and filter predicates used in Oracle?
If I understand correctly, “access” is used to determine which data blocks need to be read, and “filter” is applied after the blocks are read. Hence, filtering is “evil”. In the example of Predicate Information section of the execution plan below:
How is filter and access in execution plan?
The access bit is stopping at the like and the between. We’d have to start skipping around in the index for that – so it becomes a filter – it is done sort of during the access, but it is a filter of all of the data accessed by the prior bit of the predicate. it doesn’t mean it is actually doing it twice.
How many rows does Oracle expect to filter?
Oracle expects to have fetched only 1 row from the Index Range Scan (ACCESS), so it expects to apply the FILTER only once. Negligible cost. In the example below, the additional of the FILTER against 7,949 rows adds 160 to the COST.
Is the cost of a filter negligible in Oracle?
The “cost” of the additional FILTER for ‘SCOTT’ is negligible in this (Tom’s) example so the query plan cost doesn’t increase. Oracle expects to have fetched only 1 row from the Index Range Scan (ACCESS), so it expects to apply the FILTER only once.