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When doing initial data load sometimes it is OK to relax crash-recovery guarantees. We can disable WAL for particular cache, cache group or data region, then load data, then enable it again. This mode could increase data loading time by a factor of 2x-4x.

Duplicate PK indexes

Currently we have single PK index per physical cache plus 1 additional PK index per table. It means that in typical case when cache doesn't belong to any group, we will have two PK indexes instead of one. This slows down updates. We should try removing H2 PK index altogether. This should be done carefully, so that inline optimization feature is not lost.

Optimize CREATE INDEX

Secondary indexes negatively affects write performance. Common pattern is to drop indexes, load data and then create indexes again. This doesn't work for Ignite at the moment because index creation is slow. First, we create index adding entries one-by-one. Every addition require walking through B+Tree from the top. Instead, we can create sorted batches of entries and add multiple entries to index in one hop. Second, index is created through iteration over primary index. This is less then efficient, especially for persistent caches, due to additional jumps from primary index to data page. Instead, we can try iterating through data pages, rather than through primary index. Last, we can try creating index from multiple threads, when every thread will process predefined set of partitions.

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• IGNITE-6412 Bypass GridCacheMapEntry altogether when doing data loadIGNITE-6409 Bypass H2 index when doing updates 
• IGNITE-6410 Add data to new pages rather to existing pages to minimize free-list overhead

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