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https://issues.apache.org/jira/browse/PIG-3095?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13533168#comment-13533168
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Cheolsoo Park commented on PIG-3095:
------------------------------------
Hello Nick,
Thank you very much for the patch! I have a few comments:
- The [guava doc|http://code.google.com/p/guava-libraries/wiki/CachesExplained]
says "If you have defined a CacheLoader that does not declare any checked
exceptions then you can perform cache lookups using getUnchecked(K)".
{code}
private static final class Which extends CacheLoader<String, String> {
public String load(String file) {
...
} catch (Exception e) {}
return null;
}
}
{code}
Since {{Which.load()}} does not declare any checked exceptions, can't we use
{{getUnchecked()}} without the {{try/catch}} block? In fact, I think that no
exception will be ever caught by the following {{catch}} since {{Which.load()}}
already catches any exception. Please correct me if I am wrong.
{code}
try {
argPath = whichCache.getUnchecked(arg);
} catch(ExecutionException e) {
argPath = null;
}
{code}
With this change, "{{import java.util.concurrent.ExecutionException}}" is not
needed.
- Can you please remove the following statement since it's unused?
{code}
import com.google.common.cache.Cache;
{code}
- Can you please fix indentation in {{CacheLoader}}? This is probably because
you used "{{git diff -w}}".
{code}
private static final class Which extends CacheLoader<String, String> {
public String load(String file) {
...
}
}
{code}
> "which" is called many, many times for each Pig STREAM statement
> ----------------------------------------------------------------
>
> Key: PIG-3095
> URL: https://issues.apache.org/jira/browse/PIG-3095
> Project: Pig
> Issue Type: Bug
> Components: grunt, impl
> Affects Versions: 0.12
> Reporter: Nick White
> Assignee: Nick White
> Labels: patch, performance
> Fix For: 0.12
>
> Attachments: PIG-3095.patch
>
>
> STREAM statements are checked by the LogicalPlanBuilder as it comes across
> them - and these checks include running the system utility "which". However,
> due to the backtracking parsing mechanism "which" is called repeatedly with
> the same arguments (I noticed this while profiling a script with 4 STREAM
> statements - "which" was run over 230 times!). The attached patch just caches
> the return value of "which", reducing the overhead of running a system
> process to a Map lookup.
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