The concept of indexing a column in SharePoint is
somewhat same as you can index a column in database table. The internal working
and methodology to use and maintain the index column is different than how it
works in case of Database indexes.
In General index on a column help you locate the row
or item quick and in efficient manner and avoid scanning of several other rows.
And it help improve the performance of a large list or library. When you are
writing a query on your List or you are creating a filtered view, you can use
the index columns as filter criteria by which you can quickly retrieve the item
you want.
Also as a good practices you should not end up
creating several columns of your list as index columns, there has to be logical
decision on that, you can take a look at the Type of the column, values of the
columns, how the value of the column is used, is it used in filter criteria’s
at several other places, keep in mind that each additional column index
consumes extra resources in database and add some overheads on SharePoint to
perform some additional operations to maintain the indexes. It is very
important that you take a look at the usability of the column across all the
views, filters criteria where is most commonly used as to filter the
information for retrieval. And accordingly you can decided if you want to create
the column as indexed column. However SharePoint has imposed some limitation on
how many and on what you can create an index column. In SharePoint list or
library you can index up to 20 columns.
The following table summarizes what columns can and
cannot be indexed.
Column Types that can be indexed
|
Single line of text
|
Choice (single value)
|
Number
|
Currency
|
Date and Time
|
Lookup (single value)
|
Person or Group (single value)
|
Yes/No
|
Managed Metadata
|
Column Types that can NOT be indexed
|
Multiple lines of text
|
Choice (multi-valued)
|
Calculated
|
Hyperlink or Picture
|
Custom Columns
|
Lookup (multi-valued)
|
Person or Group (multi-valued)
|
External data
|
