[jira] [Resolved] (ORC-362) String direct length streams gets some values even if data is null

["Owen O'Malley (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ORC-362?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Owen O'Malley resolved ORC-362.
-------------------------------
    Resolution: Not A Problem

The indexes and streams are correct. We really should extend the ORC tools to interpret the indexes for the users. We should consider how to improve the indexes in ORCv2 to make them more understandable.

> String direct length streams gets some values even if data is null
> ------------------------------------------------------------------
>
>                 Key: ORC-362
>                 URL: https://issues.apache.org/jira/browse/ORC-362
>             Project: ORC
>          Issue Type: Bug
>    Affects Versions: 1.4.3
>            Reporter: Prasanth Jayachandran
>            Priority: Major
>
> Observed this in one of the orc files recently.
> Looking at the orcfiledump (compression is NONE) something looks odd
> {code:java}
>     Stream: column 2 section PRESENT start: 13976 length 80
>     Stream: column 2 section DATA start: 14056 length 541
>     Stream: column 2 section LENGTH start: 14597 length 13
> ..
> ..
> ..
>     Row group indices for column 2:
>       Entry 0: count: 4 hasNull: true min: a max: z sum: 157 positions: 0,0,0,0,0,0
>       Entry 1: count: 5 hasNull: true min: a max: z sum: 314 positions: 26,111,0,157,0,4
>       Entry 2: count: 2 hasNull: true min: a max: z sum: 70 positions: 52,62,0,471,0,9
>       Entry 3: count: 0 hasNull: true positions: 78,16,0,541,0,11
> {code}
> If we look at Entry 3 (last entry) and related the stream positions, last entry is all nulls, the corresponding data stream ended at 541 offset (which is same as length). Data stream looks correct. But now if we look at length stream, the position is recorded as 11 in last entry but the length is actually 13 (this last 2 bytes is not expected). If there is no data the length stream is supposedly not record anything. If the data is null, only isPresent stream is expected to have an entry. Looks like orc writer is writing entries to length stream even if data is null (probably recording 0 lengths).



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