The SQL Server query optimizer relies on statistics to estimate row counts and choose efficient query plans. When statistics become stale—because of data modifications that exceed an internal threshold, or because they have not been updated for an extended period—the optimizer may generate suboptimal execution plans, causing queries to slow down unpredictably. The Statistics tab in Autonomy Services gives you a consolidated view of statistics health across your instance so you can identify and fix stale statistics before they affect performance.
Prerequisites
Before you begin, ensure that:
Your RDS instance does not run SQL Server 2008 R2 with cloud disks
View statistics on the Statistics tab
Go to the Instances page. In the top navigation bar, select the region where the instance resides, find the instance, and click its ID.
In the left-side navigation pane, choose Autonomy Services > Performance Optimization.
Click the Statistics tab.
The Statistics tab is divided into three sections: Statistics Overview, Statistics Not Updated, and the statistics table.
Statistics Overview section
The Statistics Overview section shows a health summary for your instance.
| Parameter | Description |
|---|---|
| Total Statistics | The total number of statistics collected from the instance. |
| Not Updated for More Than 7 Days | The number of statistics not updated in the past seven days. |
| Not Updated for More Than 14 Days | The number of statistics not updated in the past 14 days. |
| Not Updated for More Than 30 Days | The number of statistics not updated in the past 30 days. |
| Data Updated At | The time at which the performance statistics were last generated. |
| Recollect | If the statistics are outdated, click Recollect, and then click OK in the confirmation dialog. The system re-collects statistics. After a few minutes, refresh the page to see the updated results. |
| Save as PDF File | Saves the current statistics view to your computer as a PDF file. |
Statistics Not Updated section
The Statistics Not Updated section uses charts to show how many statistics have fallen behind.
| Chart | Description |
|---|---|
| Statistics Not Updated | A column chart showing the number of statistics not updated for more than 1 day, 7 days, 14 days, and 30 days. If no statistics have been updated within 30 days, update them immediately. |
| Statistics Not Updated in Percentages | A pie chart showing the percentage breakdown of statistics not updated for more than 1 day, 7 days, 14 days, and 30 days. |
Statistics table
The statistics table lists every statistic collected from the instance, along with its staleness and available actions.
| Parameter | Description |
|---|---|
| Table Name | The fully qualified name of the data table, in the format database_name.schema_name.object_name. |
| Statistics Name | The name of the statistic. |
| Column Name | The name of the column from which the statistic is collected. |
| Last Update Time | The most recent update time. If a statistic has not been updated for more than 14 days, update it manually. |
| Actions | Available operations: Obtain Histogram and Update. |
Actions details:
Obtain Histogram: View the distribution of the statistics about the statistical item.
Update: View the updated statistics about the statistical item.
Read a histogram
Click Obtain Histogram in the Actions column to open the histogram for a statistic.
Example: In the histogram above, the Avg_RangeRows value for the UQ__students__DDDFDD3782789355 index on the SalesPersonID column of testdb01.dbo.students fluctuates sharply. This pattern indicates data skew, which can cause the optimizer to generate a poor query plan. To correct the optimizer's estimates, click Update in the Actions column for that statistic.