[jira] [Created] (IGNITE-17855) Implement inline size calculation for B+tree

["Kirill Tkalenko (Jira)" <ji...@apache.org>]

Kirill Tkalenko created IGNITE-17855:
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             Summary: Implement inline size calculation for B+tree
                 Key: IGNITE-17855
                 URL: https://issues.apache.org/jira/browse/IGNITE-17855
             Project: Ignite
          Issue Type: Task
            Reporter: Kirill Tkalenko
            Assignee: Kirill Tkalenko
             Fix For: 3.0.0-alpha6


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).



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