Github user denine99 commented on a diff in the pull request:
https://github.com/apache/accumulo/pull/33#discussion_r29169461
--- 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 --
The statement
> "An iterator which doesn't modify the Key from its source doesn't need to
copy it"
does not sound safe because the base iterators may change the data that the
Key object points to in order to reuse the same underlying char[] and the same
object.
How about this: "An iterator that does not use a Key obtained from
`getTopKey()` after calling `next()` on its source iterator (and does not use
the underlying char[] of the Key), does not need to copy the data from the Key
and may use the original object reference. Ditto for Value."
It's a wordy statement but we need all the clauses ~.~
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