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From "Holger Stratmann (JIRA)" <>
Subject [jira] [Commented] (CSV-131) Save positions of records to enable random access
Date Wed, 29 Oct 2014 08:34:33 GMT


Holger Stratmann commented on CSV-131:

sorry for taking so long to comment - I was waiting for other people's comments, was busy
and on vacation... I probably don't have time today, but will comment soon... first thoughts:
I came to the conclusion that we *don't* need the setters and it would be nice and clean solution
passing these via an alternate constructor. Wanted to prepare an alternative patch for that...

For decorator: Hmm, from the top of my head, I don't think that would work well. The decorator
wouldn't really *add* any functionality. The parser itself does not seek (that is a different
class that I did indeed implement as a decorator (of sorts)). Also, it needs access to functionality
that is not currently exposed. On top of that, the CSVRecords have only final fields so the
"decorator" would have to overwrite huge amounts of code to create different CSVRecords...
or you'd have to make the record number and position writeable (which doesn't seem to be really
I'll come back with a more thorough analysis as soon as I can... 

> Save positions of records to enable random access
> -------------------------------------------------
>                 Key: CSV-131
>                 URL:
>             Project: Commons CSV
>          Issue Type: Improvement
>          Components: Parser
>    Affects Versions: 1.1
>            Reporter: Holger Stratmann
>            Priority: Minor
>         Attachments: CSV-131-gg-0.diff, PositionTrackingFull_v101_20140910.patch, PositionTrackingTest_20140907.patch,
PositionTracking_20140907.patch, ggregory-CSV-131-parser-and-record.diff
>   Original Estimate: 1h
>  Remaining Estimate: 1h
> It would be good to have {{CSVRecord}} save its position in the source stream.
> Reason: Knowing the position of the records would enable random access to retrieve records
from the source (after reading it once to build an index) if the file is too large to be read
into memory (or if we don't want to read the full file to access a record in the middle).
> Additional info: I have created a "random access csv reader" and a "csv viewer" (Swing)
for arbitrarily large CSV files. It requires one additional scan of the file to build an index
(multi-byte charsets supported). The index can be saved to a file so it only needs to be built
once. Because the lexer uses a BufferedReader, we need "internal information" to know where
each record starts.
> The change to "core" is minor: one field in {{CSVRecord}}s and some associated methods
to store the position.
> Patch will be attached.
> Code for random access (both UI and non-UI) will be proposed (and possibly submitted)
as a separate issue. It could also be an independent add-on but requires this one little change
to Commons CSV.

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