Github user dyozie commented on a diff in the pull request:
https://github.com/apache/incubator-hawq-docs/pull/59#discussion_r87915764
--- Diff: bestpractices/querying_data_bestpractices.html.md.erb ---
@@ -4,6 +4,23 @@ title: Best Practices for Querying Data
To obtain the best results when querying data in HAWQ, review the best
practices described in this topic.
+## <a id="virtual_seg_performance"></a>Factors Impacting Query Performance
+
+The number of virtual segments used for a query directly impacts the
query's performance. The following factors can impact the degree of parallelism
of a query:
+
+- **Cost of the query**. Small queries use fewer segments and larger
queries use more segments. Some techniques used in defining resource queues can
influence the number of both virtual segments and general resources allocated
to queries. For more information, see [Best Practices for Using Resource
Queues](managing_resources_bestpractices.html#topic_hvd_pls_wv).
+- **Available resources at query time**. If more resources are available
in the resource queue, those resources will be used.
+- **Hash table and bucket number**. If the query involves only
hash-distributed tables, the query's parallelism is fixed (equal to the hash
table bucket number) under the following conditions:
+ - the bucket number (bucketnum) configured for all the hash tables is
the same bucket number for all tables
--- End diff --
Initial-cap these bullets. Also, remote "bucket number for all tables"
from the first bullet (is redundant).
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