[IGNITE-17855] Implement inline size calculation for B+tree

• Type: Task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.0.0-beta1
• Labels: ignite-3
• Epic Link: Indexes optimizations
• Assignee: Kirill Tkalenko
• Reporter: Kirill Tkalenko
• Reviewer: Ivan Bessonov
• Created: 07/Oct/22 17:45
• Updated: 13/Oct/22 12:01
• Resolved: 11/Oct/22 13:57

Description

It is necessary to implement an efficient inline size calculation for indexes.

Since the indexes will be stored in the BplusTree, we need to take into account that they will be stored in the BplusInnerIo and BplusLeafIo, so we need to calculate the effective (in the general case) size of item for storing indexes.

To calculate the size of an element, we need to take into account:

• Minimum number of items in a BplusInnerIo must be 2;
• Size of the entire tuple (index columns) must not exceed 2 KB;
  • Class size is 2 bytes to cover most cases;
  • If the user has not set a limit for variable length columns, then consider it 10 bytes;
• If there are columns of variable length and we still have space in the BplusInnerIo and BplusLeafIo, then we can increase the size of the item without compromising the leaf (i.e. do not decrease the number of items in it).

Issue Links

• is a child of: IGNITE-17536 Implement BinaryTuple inlining in a hash index B+Tree
• links to: GitHub Pull Request #1179