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https://issues.apache.org/jira/browse/PIG-3627?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13889134#comment-13889134
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Nezih Yigitbasi commented on PIG-3627:
--------------------------------------
Cheolsoo, I checked the link Jay posted in his previous comment and after some
digging it seems like the NULL schemas come from the STRSPLIT function, not
from the LOAD function. Jay uses FLATTEN(STRSPLIT(...)) in his script and
STRSPLIT returns a tuple without any internal schema (the schema of the
internal elements are NULL).
> Json storage : Doesn't work in cases , where other Store Functions (like
> PigStorage / AvroStorage) do work.
> ------------------------------------------------------------------------------------------------------------
>
> Key: PIG-3627
> URL: https://issues.apache.org/jira/browse/PIG-3627
> Project: Pig
> Issue Type: Bug
> Reporter: jay vyas
>
> The following query
> {code:title=Bar.java|borderStyle=solid}
> pigServer.registerQuery(
> "uniqcnt = foreach transactionsG {"+
> "sym = transactions.product ;"+
> "dsym = distinct sym ;"+
> "generate flatten(dsym.product) as product,
> COUNT(dsym) as count ;" +
> "};");
> {code}
> Results in the schema:
> {code}
> Schema : {product: NULL,count: long}
> {code}
> This schema, is storable using AvroStorage or PigStorage, but it fails if
> stored using JsonStorage:
> {code}
> Failed to parse: <line 1, column 8> Syntax error, unexpected symbol at or
> near ','
> at
> org.apache.pig.parser.QueryParserDriver.parseSchema(QueryParserDriver.java:94)
> at
> org.apache.pig.parser.QueryParserDriver.parseSchema(QueryParserDriver.java:108)
> at org.apache.pig.impl.util.Utils.parseSchema(Utils.java:208)
> at org.apache.pig.impl.util.Utils.getSchemaFromString(Utils.java:182)
> at
> org.apache.pig.builtin.JsonStorage.prepareToWrite(JsonStorage.java:140)
> at
> org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigOutputFormat$PigRecordWriter.<init>(PigOutputFormat.java:125)
> at
> org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigOutputFormat.getRecordWriter(PigOutputFormat.java:86)
> at
> org.apache.hadoop.mapred.ReduceTask.runNewReducer(ReduceTask.java:553)
> at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:408)
> at
> org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:216)
> {code}
> It appears that JsonStorage is thus less robust than the other storage
> formats. Can we confirm or deny if some types of data structures do/ do not
> work with JsonStorage?
> So,I suggest:
> 1) Ideally, I would think JsonStorage should support the same data that other
> Storage functions support.
> the next best thing:
> 2) Maybe a wiki page of examples that can / cannot work with JsonStorage
> and/or a better error message would be sufficient to solve this "bug".
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