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From "Anthony Hsu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-13132) Hive should lazily load and cache metastore (permanent) functions
Date Thu, 25 Feb 2016 18:54:18 GMT

    [ https://issues.apache.org/jira/browse/HIVE-13132?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15167639#comment-15167639
] 

Anthony Hsu commented on HIVE-13132:
------------------------------------

Thanks for the review, [~alangates].

# I tested and unfortunately, HIVE-2573 does NOT solve this issue. A stacktrace in jdb shows
all functions are loaded during CliDriver start-up:
{noformat}
main[1] where
  [1] org.apache.hadoop.hive.ql.metadata.Hive.reloadFunctions (Hive.java:173)
  [2] org.apache.hadoop.hive.ql.metadata.Hive.<clinit> (Hive.java:166)
  [3] org.apache.hadoop.hive.ql.session.SessionState.start (SessionState.java:503)
  [4] org.apache.hadoop.hive.cli.CliDriver.run (CliDriver.java:677)
  [5] org.apache.hadoop.hive.cli.CliDriver.main (CliDriver.java:621)
  [6] sun.reflect.NativeMethodAccessorImpl.invoke0 (native method)
  [7] sun.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
  [8] sun.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
  [9] java.lang.reflect.Method.invoke (Method.java:483)
  [10] org.apache.hadoop.util.RunJar.run (RunJar.java:221)
  [11] org.apache.hadoop.util.RunJar.main (RunJar.java:136)
{noformat}
# My fix is a bit hacky and only works on the Hive 0.13.1 branch. I basically changed the
CliDriver initialization code to use {{FunctionRegistry.getFunctionNames(String funcPatternStr)}}
instead of {{FunctionRegistry.getFunctionNames()}}. In the Hive 0.13.1 branch, the former
does NOT search the metastore while the latter does. This is no longer the case in trunk.
# I don't have much experience with HS2 but I will take a look.

I'll work on a cleaner solution that removes the pre-loading of metastore functions from the
CliDriver initialization code path. Suggestions welcome.

> Hive should lazily load and cache metastore (permanent) functions
> -----------------------------------------------------------------
>
>                 Key: HIVE-13132
>                 URL: https://issues.apache.org/jira/browse/HIVE-13132
>             Project: Hive
>          Issue Type: Improvement
>    Affects Versions: 0.13.1
>            Reporter: Anthony Hsu
>            Assignee: Anthony Hsu
>         Attachments: HIVE-13132.1.patch
>
>
> In Hive 0.13.1, we have noticed that as the number of databases increases, the start-up
time of the Hive interactive shell increases. This is because during start-up, all databases
are iterated over to fetch the permanent functions to display in the {{SHOW FUNCTIONS}} output.
> {noformat:title=FunctionRegistry.java}
>   private static Set<String> getFunctionNames(boolean searchMetastore) {
>     Set<String> functionNames = mFunctions.keySet();
>     if (searchMetastore) {
>       functionNames = new HashSet<String>(functionNames);
>       try {
>         Hive db = getHive();
>         List<String> dbNames = db.getAllDatabases();
>         for (String dbName : dbNames) {
>           List<String> funcNames = db.getFunctions(dbName, "*");
>           for (String funcName : funcNames) {
>             functionNames.add(FunctionUtils.qualifyFunctionName(funcName, dbName));
>           }
>         }
>       } catch (Exception e) {
>         LOG.error(e);
>         // Continue on, we can still return the functions we've gotten to this point.
>       }
>     }
>     return functionNames;
>   }
> {noformat}
> Instead of eagerly loading all metastore functions, we should only load them the first
time {{SHOW FUNCTIONS}} is invoked. We should also cache the results.
> Note that this issue may have been fixed by HIVE-2573, though I haven't verified this.



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