accumulo-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From joshelser <...@git.apache.org>
Subject [GitHub] accumulo pull request: ACCUMULO-3646 Update iterator doc on entrie...
Date Mon, 27 Apr 2015 16:14:05 GMT
Github user joshelser commented on a diff in the pull request:

    https://github.com/apache/accumulo/pull/33#discussion_r29161718
  
    --- Diff: docs/src/main/asciidoc/chapters/iterator_design.txt ---
    @@ -145,8 +146,16 @@ alter the internal state of the Iterator.
     
     These methods simply return the current Key-Value pair for this iterator. If `hasTop`
returns true,
     both of these methods should return non-null objects. If `hasTop` returns false, it is
undefined
    -what these methods should return. Multiple calls to these methods should not alter the
state
    -of the Iterator like `hasTop`.
    +what these methods should return. Like `hasTop`, multiple calls to these methods should
not alter 
    +the state of the Iterator.
    +
    +When saving a Key or Value from a source iterator's `getTopKey` or `getTopValue` methods
    +for use after calling `next` on the source iterator (e.g., when cacheing keys or values
    +from the source iterator), it is important to copy the Key or Value into a new object

    +because the source iterator may reuse the Key or Value objects for performance reasons.
    --- End diff --
    
    Great, thanks Dylan. My memory isn't what it should be :).
    
    > I think some iterators do this frequently
    
    I took a gander at the "user" iterators, and I was a little surprised to see as many iterators
doing a copy in some form or another. Perhaps I'm being overly sensitive on the performance
concerns. Maybe my concern could be reworded: are there cases in which a user doesn't need
to copy the Key we could outline?
    
    "An iterator which doesn't modify the Key from its source doesn't need to copy it" ? This
would catch cases like value transformations. What do you think? Is that a safe clarification
to make?


---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at infrastructure@apache.org or file a JIRA ticket
with INFRA.
---

Mime
View raw message