---
title:  Query Debugging
---

<!--
Licensed to the Apache Software Foundation (ASF) under one or more
contributor license agreements.  See the NOTICE file distributed with
this work for additional information regarding copyright ownership.
The ASF licenses this file to You under the Apache License, Version 2.0
(the "License"); you may not use this file except in compliance with
the License.  You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->

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
```

When the query is executed, <%=vars.product_name%> will log a message in `$GEMFIRE_DIR/system.log` with the following information:

``` 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 /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.


