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Posted to commits@impala.apache.org by jo...@apache.org on 2019/02/16 01:20:18 UTC
[impala] 03/04: IMPALA-8203: [DOCS] Clarified a few points in
DISABLE_CODEGEN
This is an automated email from the ASF dual-hosted git repository.
joemcdonnell pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/impala.git
commit 99e2d5056c977ed6d9c4b2f65febd183b3b0e64c
Author: Alex Rodoni <ar...@cloudera.com>
AuthorDate: Thu Feb 14 18:04:53 2019 -0800
IMPALA-8203: [DOCS] Clarified a few points in DISABLE_CODEGEN
Change-Id: Ic10fd66d8a83d10c0900e93a00241d532902a759
Reviewed-on: http://gerrit.cloudera.org:8080/12496
Tested-by: Impala Public Jenkins <im...@cloudera.com>
Reviewed-by: Alex Rodoni <ar...@cloudera.com>
---
docs/topics/impala_disable_codegen.xml | 50 ++++++++++++++++++++++++++--------
1 file changed, 38 insertions(+), 12 deletions(-)
diff --git a/docs/topics/impala_disable_codegen.xml b/docs/topics/impala_disable_codegen.xml
index 82add52..7410b6c 100644
--- a/docs/topics/impala_disable_codegen.xml
+++ b/docs/topics/impala_disable_codegen.xml
@@ -21,7 +21,13 @@ under the License.
<concept id="disable_codegen">
<title>DISABLE_CODEGEN Query Option</title>
- <titlealts audience="PDF"><navtitle>DISABLE_CODEGEN</navtitle></titlealts>
+
+ <titlealts audience="PDF">
+
+ <navtitle>DISABLE_CODEGEN</navtitle>
+
+ </titlealts>
+
<prolog>
<metadata>
<data name="Category" value="Impala"/>
@@ -34,23 +40,43 @@ under the License.
<conbody>
<p>
- <indexterm audience="hidden">DISABLE_CODEGEN query option</indexterm>
- This is a debug option, intended for diagnosing and working around issues that cause crashes. If a query
- fails with an <q>illegal instruction</q> or other hardware-specific message, try setting
- <codeph>DISABLE_CODEGEN=true</codeph> and running the query again. If the query succeeds only when the
- <codeph>DISABLE_CODEGEN</codeph> option is turned on, submit the problem to <keyword keyref="support_org"/> and include that
- detail in the problem report. Do not otherwise run with this setting turned on, because it results in lower
- overall performance.
+ The <codeph>DISABLE_CODEGEN</codeph> is a debug option, and it's used to work around any
+ issues with Impala's runtime code generation. If a query fails with an <q>illegal
+ instruction</q> or other hardware-specific message, try setting
+ <codeph>DISABLE_CODEGEN=true</codeph> and running the query again. If the query succeeds
+ only when the <codeph>DISABLE_CODEGEN</codeph> option is turned on, submit the problem to
+ <keyword keyref="support_org"> </keyword> and include that detail in the problem report.
</p>
<p>
- Because the code generation phase adds a small amount of overhead for each query, you might turn on the
- <codeph>DISABLE_CODEGEN</codeph> option to achieve maximum throughput when running many short-lived queries
- against small tables.
+ Most queries will run significantly slower with <codeph>DISABLE_CODEGEN=true</codeph>.
+ </p>
+
+ <p>
+ In Impala 2.10 and higher, the <codeph>DISABLE_CODEGEN_ROWS_THRESHOLD</codeph>
+ optimisation automatically disables codegen for small queries because short-running
+ queries may run faster without the overhead of codegen.
+ </p>
+
+ <p>
+ The following values are supported:
+ <ul>
+ <li>
+ <codeph>TRUE</codeph> or <codeph>1</codeph>: Disables codegen.
+ </li>
+
+ <li>
+ <codeph>FALSE</codeph> or <codeph>0</codeph>: Enables codegen.
+ </li>
+ </ul>
+ </p>
+
+ <p>
+ <b>Type:</b> Boolean
</p>
- <p conref="../shared/impala_common.xml#common/type_boolean"/>
<p conref="../shared/impala_common.xml#common/default_false_0"/>
</conbody>
+
</concept>