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https://issues.apache.org/jira/browse/PIG-1321?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Daniel Dai updated PIG-1321:
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Attachment: jira-1321-3.patch
Repost the pre-condition:
1. two consecutive foreach statements.
2. the second foreach statement is a simple inner plan in which the ognly
statement is a GENERATE statement. In other words, the second foreach statement
must be something like "FOREACH A GENERATE ...."
3. The first foreach statement cannot contain flatten due to its complexity
4. No 1st foreach output is referred more than once in second foreach, eg: "B =
foreach xxxx; C = foreach B generate $0, $1, $0" will not be merged. The reason
if we merge, $0 will be calculated twice, which defeat the benefit of merging.
All tests pass. test-patch result:
[exec] +1 overall.
[exec]
[exec] +1 @author. The patch does not contain any @author tags.
[exec]
[exec] +1 tests included. The patch appears to include 3 new or
modified tests.
[exec]
[exec] +1 javadoc. The javadoc tool did not generate any warning
messages.
[exec]
[exec] +1 javac. The applied patch does not increase the total number
of javac compiler warnings.
[exec]
[exec] +1 findbugs. The patch does not introduce any new Findbugs
warnings.
[exec]
[exec] +1 release audit. The applied patch does not increase the
total number of release audit warnings.
> Logical Optimizer: Merge cascading foreach
> ------------------------------------------
>
> Key: PIG-1321
> URL: https://issues.apache.org/jira/browse/PIG-1321
> Project: Pig
> Issue Type: Sub-task
> Components: impl
> Affects Versions: 0.7.0
> Reporter: Daniel Dai
> Assignee: Xuefu Zhang
> Fix For: 0.8.0
>
> Attachments: jira-1321-2.patch, jira-1321-3.patch, pig-1321.patch
>
>
> We can merge consecutive foreach statement.
> Eg:
> b = foreach a generate a0#'key1' as b0, a0#'key2' as b1, a1;
> c = foreach b generate b0#'kk1', b0#'kk2', b1, a1;
> => c = foreach a generate a0#'key1'#'kk1', a0#'key1'#'kk2', a0#'key2', a1;
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