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https://issues.apache.org/jira/browse/PIG-627?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12680997#action_12680997
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Pradeep Kamath commented on PIG-627:
------------------------------------
Sorry about the misunderstanding, I think I looked at a different patch. After
reviewing the right patch, here are some comments:
The patch throws Java Exceptions like IllegalStateException. This should be
replaced with the appropriate Exception class (like MRCompilerException) as
specified in
http://wiki.apache.org/pig/PigErrorHandlingFunctionalSpecification. The
exception should be created with the error code, error source and error message
constructor. New error codes should be introduced if one of the existing ones
in
http://wiki.apache.org/pig/PigErrorHandlingFunctionalSpecification#head-9f71d78d362c3307711f98ec9db3ee12b55e92f6
cannot be used. If new codes are introduced, the wiki table should be updated.
The following can be used to check for file existence in
BinStorage.determineSchema() - only in the case where the file does not exist,
null should be returned
{code}
public static boolean fileExists(String filename, DataStorage store)
throws IOException {
ElementDescriptor elem = store.asElement(filename);
return elem.exists() || globMatchesFiles(elem, store);
}
{code}
Instead of introducing a rootsFirst attribute in DependencyOrderWalker, I
wonder if we should have a ReverseDependencyOrderWalker since that is what the
rootsFirst == false case will be. If we are not visiting roots to leaf, we
really are not visiting in a dependency order - so the meaning of dependency
order is no longer honored - this can be confusing I think. By explicitly
naming the walker ReverseDependencyOrderWalker, the intent of walking from
leaves to roots is more clear I think.
In POSplit currently there is a PhysicalPlan representing the merged inner
plans (where all plans are mutually exclusive) and there is also a
List<PhysicalPlan> which has the same information in the form of a List. In the
rest of pig code, inner plans have always been modelled as List<PhysicalPlan>.
For consistency, it is better to just have a List<PhysicalPlan> to represent
the inner plans.
> PERFORMANCE: multi-query optimization
> -------------------------------------
>
> Key: PIG-627
> URL: https://issues.apache.org/jira/browse/PIG-627
> Project: Pig
> Issue Type: Improvement
> Affects Versions: 1.0.0
> Reporter: Olga Natkovich
> Attachments: file_cmds-0305.patch, multi-store-0303.patch,
> multi-store-0304.patch, multiquery_0223.patch, multiquery_0224.patch,
> multiquery_0306.patch
>
>
> Currently, if your Pig script contains multiple stores and some shared
> computation, Pig will execute several independent queries. For instance:
> A = load 'data' as (a, b, c);
> B = filter A by a > 5;
> store B into 'output1';
> C = group B by b;
> store C into 'output2';
> This script will result in map-only job that generated output1 followed by a
> map-reduce job that generated output2. As the resuld data is read, parsed and
> filetered twice which is unnecessary and costly.
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