---
title:  Query Debugging
---

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You can debug a specific query at the query level by adding the `<trace>` keyword before the query string that you want to debug.

Here is an example:

``` pre
<trace> select * from /exampleRegion
```

You can also write:

``` pre
<TRACE> select * from /exampleRegion
```

Before the query is executed and once it completes, <%=vars.product_name%> will log messages in `$GEMFIRE_DIR/system.log` with the following information:

``` pre
[info 2011/08/29 11:24:35.462 PDT CqServer <main> tid=0x1] Starting query: select * from /exampleRegion

[info 2011/08/29 11:24:35.472 PDT CqServer <main> tid=0x1] Query Executed in 9.619656 ms; rowCount = 99; indexesUsed(0) "select * from /exampleRegion"
```

If you want to enable debugging for all queries, you can enable query execution logging by setting a System property on the command line during start-up:

``` pre
gfsh>start server --name=server_name -–J=-Dgemfire.Query.VERBOSE=true
```

Or you can set the property programmatically:

``` pre
System.setProperty("gemfire.Query.VERBOSE","true");
```

As an example, let us say you have an EmployeeRegion that that contains Employee objects as values and the objects have public fields in them like ID and status.

``` pre
Employee.java
Class Employee {
 public int ID;
 public String status;
 - - - - - -
 - - - - - -
}
```

In addition, you have created the following indexes for the region:

``` pre
<index name="sampleIndex-1">
<functional from-clause="/test " expression="ID"/>
</index>
<index name="sampleIndex-2">
<functional from-clause="/test " expression="status"/>
</index>
```

After you have set `gemfire.Query.VERBOSE` to "true", you could see the following debug messages in the logs after running queries on the EmployeeRegion or its indexes:

-   If indexes are not used in the query execution, you would see a debug message like this:

    ``` pre
    [info 2011/08/29 11:24:35.472 PDT CqServer <main> tid=0x1] Query Executed in 9.619656 ms; rowCount = 99; indexesUsed(0) "select * from /test k where ID > 0 and status='active'"
    ```

-   When single index is used in query execution, you might see a debug message like this:

    ``` pre
    [info 2011/08/29 11:24:35.472 PDT CqServer <main> tid=0x1] Query Executed in 101.43499 ms; rowCount = 199; indexesUsed(1):sampleIndex-1(Results: 199) "select count *   from /test k where ID > 0"
    ```

-   When multiple indexes are used by a query, you might see a debug message like this:

    ``` pre
    [info 2011/08/29 11:24:35.472 PDT CqServer <main> tid=0x1] Query Executed in 79.43847 ms; rowCount = 199; indexesUsed(2):sampleIndex-2(Results: 100),sampleIndex-1(Results: 199) "select * from /test k where ID > 0 OR status='active'"
    ```

In above log messages, the following information is provided:

-   "rowCount" represents ResultSet size for the query.
-   "indexesUsed(\\n) " shows n indexes were used for finding the results of the query.
-   Each index name and its corresponding results are reported respectively.
-   The log can be identified with the original query string itself appended in the end.