Github user dyozie commented on a diff in the pull request:
https://github.com/apache/incubator-hawq-docs/pull/60#discussion_r87921679
--- Diff: datamgmt/about_statistics.html.md.erb ---
@@ -142,11 +142,28 @@ There are several options for configuring HAWQ
statistics collection.
The statistics target is the size of the `most_common_vals`,
`most_common_freqs`, and `histogram_bounds` arrays for an individual column. By
default, the target is 25. The default target can be changed by setting a
server configuration parameter and the target can be set for any column using
the `ALTER TABLE` command. Larger values increase the time needed to do
`ANALYZE`, but may improve the quality of the legacy query optimizer (planner)
estimates.
-Set the system default statistics target to a different value by setting
the `default_statistics_target` server configuration parameter. The default
value is usually sufficient, and you should only raise or lower it if your
tests demonstrate that query plans improve with the new target. For example, to
raise the default statistics target from 25 to 50 you can use the `hawq config`
utility:
+Set the system default statistics target to a different value by setting
the `default_statistics_target` server configuration parameter. The default
value is usually sufficient, and you should only raise or lower it if your
tests demonstrate that query plans improve with the new target.
-``` shell
-$ hawq config -c default_statistics_target -v 50
-```
+You will perform different procedures to set server configuration
parameters for your whole HAWQ cluster depending upon whether you manage your
cluster from the command line or use Ambari. If you use Ambari to manage your
HAWQ cluster, you must ensure that you update server configuration parameters
via the Ambari Web UI only. If you manage your HAWQ cluster from the command
line, you will use the `hawq config` command line utility to set server
configuration parameters.
+
+For example, to raise the default statistics target from 25 to 50:
+
+1. If you use Ambari to manage your HAWQ cluster:
+
+ 1. Set the `default_statistics_target` configuration property to `50`
via the HAWQ service **Configs > Advanced > Custom hawq-site** drop down.
+ 2. Select **Service Actions > Restart All** to load the updated
configuration.
+2. If you manage your HAWQ cluster from the command line:
--- End diff --
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