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When is index not used in where clause?
Oracle not using index when > used in where clause. We have a relatively classic scenario where the date clause of the query generated by the application uses a “greater than” for a given date. Because there is no end clause to the date range, oracle doesn’t choose to use the date index and ends up doing a very expensive table scan instead.
Which is better using index or using index condition?
If there are any columns out of index, then Column Extra say Using Where, Using Index (in this case, Mysql need look for in data row to apply where clause). It’s better ‘Using Index Condition’.
When do you use index condition in MySQL?
Using index condition is when the where condition contains indexed and non-indexed column and the optimizer will first resolve the indexed column and will look for the rows in the table for the other condition. The 2nd approach is called index push down.
What is the effect of adding an indexed view?
The effect of adding an indexed view depends on many factors, so you need to test it. Any safe solution has the potential to increase contention, but where an indexed computed column doesn’t fit, an indexed view is often the next best option. If done well, the effect can be minimal.
Why is the index not being used in Oracle?
Run your SQL through Explain Planand confirmed that the desired index is not being used. Checked the statisticson the underlying table. Confirmed that the index exists. Oracle will ignore an index for a number of reasons, but they boil down to two possibilities:
What to do if SQL refuses to use the index?
If this simple SQL refuses to use the index, then there is a fundamental problem. Get the DBA to drop and rebuild the index. If the sample SQL above doesuse the index, then start with your original SQL and remove lines one at a time, running each successively smaller SQL through Explain Planas you go.
What to do if the index is being ignored?
Get the DBA to drop and rebuild the index. If the sample SQL above doesuse the index, then start with your original SQL and remove lines one at a time, running each successively smaller SQL through Explain Planas you go. Somewhere between the original SQL and the one above, the index will start to work.