ID | IEP-32 |
Author | |
Sponsor |
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Created | |
Status | DRAFT |
Currently batch updates on page memory level are not implemented in Ignite. Internal structures, such as BPlusTree and FreeList, do not support them. The performance of batch operations (putAll, datastreamer, preloader) can be improved by implementing batch updates on page memory level.
Profiling the current rebalancing process shows that most of the time is spent on working with FreeList and BPlusTree (details).
Currently, when updating the batch of cache entries in off heap, each of them is processed separately.
Such update in PageMemory can be divided into the following steps:
In Ignite search and update of key in tree implemented through the "invoke" operation, to understand the needs for this operation, it is necessary to describe B+ tree in more detail.
The keys of the tree (hashes) are stored on the B+ tree pages (index pages), the cache key-value (data row) itself is stored on data pages. Each item on the index page includes a link to the data page item (pageId + itemId).
In general, a B-tree supports find, put and remove operations. For put/remove, you must firstly find the point of insertion/update/removal.
So, cache entry update without invoke operation should look like this:
To prevent a redundant secondary search in the case described above the "invoke" operation was introduced. This operation has the following scheme of execution:
OffHeapManager.invoke |-> BPlusTree.invoke | | | | | | | |-> Invoke.invokeClosure() | | |-> UpdateClosure.call(foundRow) | | | |- compare entry version | | | |- newRow = create newRow on data page | | | |- treeOp = PUT/REMOVE/NOOP | | | | | \-> read treeOp -> create operation closure (Put(newRow)/Remove(row)) | | | \-> Invoke.found()/notFound() -> exec opearation closure | | \-> finishUpdate/finishRemove
Saving a cache entry on data page consists of the following operations:
Implementation should consists of two major related improvements:
Improves the time to remove/insert pages in FreeList, pages locking and update item counters.
Improves the time of searching and inserting a range of keys.
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