[IGNITE-21987] Optimize RO scan in sorted indexes

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.0.0-beta2
• Labels: ignite-3
• Ignite Flags: Docs Required, Release Notes Required
• Assignee: Philipp Shergalis
• Reporter: Ivan Bessonov
• Reviewer: Ivan Bessonov
• Created: 04/Apr/24 13:57
• Updated: 11/Apr/24 12:34
• Resolved: 11/Apr/24 12:34

Description

This issue applies to aimem/aipersist primarily. Optimization for rocksdb might be done separately.

• add new method to SortedIndexStorage, like "readOnlyScan", that returns a simple cursor
• in the implementation we should use alternative cursor implementation for RO scans - it should delegate calls to B+Tree cursor
• reuse existing tests where possible
• call new method where necessary (PartitionReplicaListener#scanSortedIndex)

IMPORTANT: we should throw an exception if somebody scans an index and IndexStorage#getNextRowIdToBuild is not null. It should be a new error, like "IndexNotBuiltException"

Issue Links

• links to: GitHub Pull Request #3566