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https://issues.apache.org/jira/browse/HIVE-5019?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14028555#comment-14028555
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Thejas M Nair commented on HIVE-5019:
-------------------------------------
In the following change, there is a bug. The tmp needs to get 'reset' after the
toString(). Not sure what the most efficient way to do that is (delete vs new
StringBuilder).
{code}
+ StringBuilder tmp = new StringBuilder("");
for (String key : properties.keySet()) {
if (properties.get(key) != null && !duplicateProps.contains(key)) {
- realProps.add(" '" + key + "'='" +
-
escapeHiveCommand(StringEscapeUtils.escapeJava(properties.get(key))) + "'");
+ tmp.append(" '");
+ tmp.append(key);
+ tmp.append("'='");
+
tmp.append(escapeHiveCommand(StringEscapeUtils.escapeJava(properties.get(key))));
+ tmp.append("'");
+ realProps.add(tmp.toString());
}
{code}
This does make the code more verbose and less readable. I am not very convinced
that in cases like the one above, the use of StringBuilder would make a
difference. The compiler would usually replace + with use of StringBuilder in
simple cases like this.
bq. Yes, they do mostly replace + with StringBuilder.append(). However this is
not always the case it seems. I ran some tests and they showed that using the
StringBuilder when appending strings is 57% faster than using the + operator
(using the StringBuffer took 122 milliseconds whilst the + operator took 284
milliseconds).
Can you please upload the test code you used ? Can you try running it longer
(say more than 5-10 seconds), so any noise is filtered out.
> Use StringBuffer instead of += (issue 1)
> ----------------------------------------
>
> Key: HIVE-5019
> URL: https://issues.apache.org/jira/browse/HIVE-5019
> Project: Hive
> Issue Type: Sub-task
> Reporter: Benjamin Jakobus
> Assignee: Benjamin Jakobus
> Attachments: HIVE-5019.2.patch.txt, HIVE-5019.3.patch.txt
>
>
> Issue 1 - use of StringBuilder over += inside loops.
> java/org/apache/hadoop/hive/ql/optimizer/physical/GenMRSkewJoinProcessor.java
> java/org/apache/hadoop/hive/ql/optimizer/ppr/PartitionPruner.java
> java/org/apache/hadoop/hive/ql/parse/PTFTranslator.java
> java/org/apache/hadoop/hive/ql/parse/SemanticAnalyzer.java
> java/org/apache/hadoop/hive/ql/parse/SemanticAnalyzer.java
> java/org/apache/hadoop/hive/ql/plan/ConditionalResolverMergeFiles.java
> java/org/apache/hadoop/hive/ql/plan/PlanUtils.java
> java/org/apache/hadoop/hive/ql/security/authorization/BitSetCheckedAuthorizationProvider.java
> java/org/apache/hadoop/hive/ql/stats/jdbc/JDBCStatsUtils.java
> java/org/apache/hadoop/hive/ql/udf/UDFLike.java
> java/org/apache/hadoop/hive/ql/udf/generic/GenericUDFSentences.java
> java/org/apache/hadoop/hive/ql/udf/generic/NumDistinctValueEstimator.java
> java/org/apache/hadoop/hive/ql/udf/ptf/NPath.java
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