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Which is an example of a redundant index?
I call redundant indexes BTREE indexes which are prefix of other index, for example KEY (A), KEY (A,B), KEY (A (10)). – First and last are redundant indexes because they are prefix of KEY (A,B)
How to identify redundant / duplicate indexes in SQL Server?
Identifying redundant indexes is a very important task for a DBA. I personally do not find any reason of having redundant indexes on databases. Otherwise, it is an over head to the system like maintaining the index/storage space etc. The challenge is to identify a redundant/duplicate index in SQL Server?
Is it bad to have duplicate indexes in a database?
Duplicate keys are bad so once you find them get rid of them. Note: Duplicate indexes apply to indexes of the same time. It may make sense to have indexes of different types to created on the same column(s) – perfect example is BTREE index and FULLTEXT index, while other combinations may also make sense.
Can a composite index span more than one column?
An index can also span more than one column: Indexes over multiple columns, also known as composite indexes, speed up queries which filter on index’s columns, but also queries which only filter on the first columns covered by the index. See the performance docs for more information.
When to change full text index in SQL Server?
When a column is added, the full-text index on the table must be repopulated in order for full-text queries against this column to work. Whether the full-text index is populated after a column is added or dropped from a full-text index depends on whether change-tracking is enabled and whether WITH NO POPULATION is specified.
When do I add a column to a full text index?
Whether the full-text index is populated after a column is added or dropped from a full-text index depends on whether change-tracking is enabled and whether WITH NO POPULATION is specified. For more information, see Interactions of Change Tracking and NO POPULATION Parameter.
When to add a long index to a short index?
Typical case when leaving short index AND adding longer one could be when you want certain query to run as index covered query (retrieve all columns from the index) – such indexes may become way too long to be efficiently used by other queries.