Plan Explorer Index Analysis

Introduction

The Plan Explorer Index Analysis tab provides a sandbox environment for planning indexing strategy relative to a specific operation in a query.

For Index Analysis to populate, the query must execute from within the Plan Explorer session, using the Get Actual Plan menu option.

Overall view of the Index Analysis tab in a Plan Explorer session

The Statement Tree and Plan Diagram

For more information, see the Integrated Plan Explorer topic. 

The Text Data Area

For more information, see the Integrated Plan Explorer topic. 

The Indexes Data Grid

The top row is the index Total Score that's based on several factors including covering, value density, sorting effectiveness, and seek-ability. 100 percent is the best possible score; however, there are some situations that prevent the possibility of a 100 percent score. One known cause is when columns are missing statistics. 

Column statistics are provided for each table column used by the query, with table columns used by the selected operation displayed in bold.

Data Grid Columns:

Columns in the grid to the right of the Predicate column all represent indexes. These include both special case indexes, as well as the indexes defined on the table.

Indexes can be modified, as well as scripted for create, drop, or drop and create. Manually update statistics using the button at the bottom of the index column.

Index Coloring:

• Shades of green indicate that the ordinal position of the column is such that a favorable operation may occur, such as a seek over a scan. Darker shades of green indicate that the column is filtered.
• Yellow indicates that the column is used in the query, and covered, but isn't part of the left subset of the index key. Included columns are also listed in yellow.
• Red indicates that the column involved isn't covered by the index.

The Parameters Data Grid

The parameters grid lists parameters used by the query. This differs from the Plan Explorer Parameters tab in that it uses tipping point logic to help determine the type of operation (Seek or Scan) that the optimizer might choose for that parameter value. This isn't an exact science, and should be used as a rough guideline.

The parameters grid provides a Test Value column that allows you to enter a new parameter value and asks for a new Estimated Plan. This allows you to test different parameter values against the plan to see if the plan shape changes given that parameter value.

The small arrows to the right of the parameter values allow you to quickly place the value of that parameter into the Test Values column.

Options for Parameters Data Grid

The Statistics Histogram Chart

The Histogram chart displays the histogram steps for the index statistics visually. This allows you to quickly spot potential parameter sniffing issues.

This chart also works in conjunction with the parameters grid, and selected parameters that are present in the histogram have their histogram buckets highlighted on the chart. This also works for parameter ranges.

Update Statistics

Update the statistics for a selected index on the Index Analysis tab by selecting the Update Statistics button . On the Update Statistics window, select  the sample mode, select a sample percentage, and then select Update to refresh the index statistics.

Update Statistics Window

Script Index

View the associated script for a selected index by selecting the Script Index button. 

Script Index Window

Script Index Window Context Menu