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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"CursorIterator design changes","articleBody":"As discussed in #153, `CursorIterator` does not reflect the usual Java iterator idiom where an `Iterable` is able to produce multiple `Iterator` instances. This restriction exists because LMDB is used to provide the elements through an underlying transaction (provided at the time `Dbi.iterate(..)` is invoked) and cursor. Due to the use of these native resources, it is impractical to effectively produce multiple arbitrary `Iterator`s from the same `Iterable`, especially given each `Iterator` would need to be individually `AutoCloseable` to release its associated LMDB cursor.\r\n\r\nIt is difficult to envisage a practical use case for reusing an `Iterable` in the first place, especially given the shared `Txn` and `KeyRange` would result in the same the data for all returned `Iterator`s anyway. Furthermore users with advanced needs are referred to `Dbi.openCursor(..)`, as this permits moving the cursor in any direction and at any time while the `Txn` remains available.\r\n\r\nWhile #153 added a simple guard to prevent acquiring multiple `Iterator` instances, the overall design remains non-idiomatic. Fundamentally `Dbi.iterate(..)` should return a class that implements `Iterable` so that the returned object can be directly and idiomatically used in an enhanced `for` statement. This would mean:\r\n\r\n* Renaming `CursorIterator` to `CursorIterable`\r\n* Implementing the `Iterable` interface on `CursorIterable`\r\n* Removing the `Iterator` interface from `CursorIterable`\r\n* Relocating the `Iterator` methods into the inner class returned from `CursorIterable.iterator()`\r\n\r\nUnfortunately these changes represent a minor breaking change for existing users. Given this is a breaking change, it's a good opportunity to remove the deprecated `IteratorType` as well. The `IteratorType` was [deprecated](https://github.com/lmdbjava/lmdbjava/blob/895fcbd044247da3164d1ee6dd35a0c7bde3dff7/src/main/java/org/lmdbjava/CursorIterator.java#L211) in LmdbJava 0.6.0 ([released July 2017](https://github.com/lmdbjava/lmdbjava/wiki/Change-Log#060-16-jul-2017)) and represents the only deprecated code currently remaining in LmdbJava.","author":{"url":"https://github.com/bp-alex","@type":"Person","name":"bp-alex"},"datePublished":"2020-04-27T01:50:17.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/154/lmdbjava/issues/154"}