Understanding SharePoint Indexing: When Does SharePoint Automatically Index Columns?

SharePoint automatically indexes columns in several instances:

1. Primary Key Columns: When you create a list, SharePoint automatically indexes the primary key column (ID field) for faster retrieval.

2. Unique Columns: Columns marked as unique are automatically indexed to enforce uniqueness.

3. Lookup Columns: Columns used as lookup columns in other lists are automatically indexed to optimize lookup queries.

4. Managed Metadata Columns: SharePoint automatically indexes managed metadata columns to enhance performance when filtering or sorting by these columns.

5. Indexed Columns in Views: Columns included in indexed views are automatically indexed to improve view performance.

6. Indexed Columns in Large Lists: In large lists, SharePoint automatically indexes frequently used columns to improve performance.

7. Date and Time Columns: Columns with date and time data types are automatically indexed to optimize date-based queries.

These automatic indexing features help improve performance and efficiency in SharePoint lists and libraries.