[impala] 03/05: IMPALA-9910: [DOCS] update retry failed queries query option

[st...@apache.org]

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commit 2e71f35b2f8e6f6cc04a8bd55991e59cda4bc373
Author: Shajini Thayasingh <st...@cloudera.com>
AuthorDate: Thu Dec 3 13:43:47 2020 -0800

    IMPALA-9910: [DOCS] update retry failed queries query option
    
    Added why cluster membership changes typically occur.
    Explained how the coordinator will retry a failed query.
    Talked about the new query option spool_all_results_for_retries.
    Incorporated corrections from Patch set 2.
    
    Change-Id: I3a65357a6e3d0bffa840b8636171a38bd9b22d17
    Reviewed-on: http://gerrit.cloudera.org:8080/16819
    Reviewed-by: Impala Public Jenkins <im...@cloudera.com>
    Tested-by: Impala Public Jenkins <im...@cloudera.com>
---
 docs/topics/impala_retry_failed_queries.xml | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/docs/topics/impala_retry_failed_queries.xml b/docs/topics/impala_retry_failed_queries.xml
index e20a327..09bb7802 100644
--- a/docs/topics/impala_retry_failed_queries.xml
+++ b/docs/topics/impala_retry_failed_queries.xml
@@ -36,14 +36,21 @@ under the License.
     <p>Use the <codeph>RETRY_FAILED_QUERIES</codeph> query option to control
       whether or not queries are transparently retried on cluster membership
       changes. </p>
-    <p>Transparent query retries will automatically trigger retries of queries
-      that fail because of a change in the Impala cluster membership. Cluster
-      membership changes typically occur when an impalad crashes, or if the
-      node is blacklisted by the Impala Coordinator.</p>
+    <p>Cluster membership changes typically occur when an impalad crashes, or if the node is
+      blacklisted by the Impala Coordinator. If a SELECT query fails due to a cluster membership
+      change, the Coordinator will cancel and unregister the running query and then launch a retry
+      of the query. For example, if one of the executor nodes fails during query execution, the query
+      fails but is transparently re-executed, either with the executor node immediately replaced, or
+      with a temporarily reduced number of executor nodes. This feature supports retrying the
+      entire query and NOT the individual query fragments. INSERT and DDL queries will NOT be
+      retried.</p>
+    <p>Note that query retry will be skipped if the query has returned any results to the client. To
+      avoid this, enable <codeph>Result Spooling</codeph> and set the
+        <codeph>spool_all_results_for_retries</codeph> query option.</p>
     <p><b>Type:</b>
       <codeph>BOOLEAN</codeph></p>
     <p><b>Default:</b>
-      <codeph>FALSE</codeph></p>
+      <codeph>TRUE</codeph></p>
     <p><b>Added in:</b>
       <keyword keyref="impala40"/></p>
     <p><b>Related information:</b>