[jira] [Commented] (IGNITE-17536) Implement BinaryTuple inlining in a hash index B+Tree

["Ivan Bessonov (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/IGNITE-17536?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17617536#comment-17617536 ] 

Ivan Bessonov commented on IGNITE-17536:
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Looks good to me, thank you!

> Implement BinaryTuple inlining in a hash index B+Tree
> -----------------------------------------------------
>
>                 Key: IGNITE-17536
>                 URL: https://issues.apache.org/jira/browse/IGNITE-17536
>             Project: Ignite
>          Issue Type: Task
>            Reporter: Kirill Tkalenko
>            Assignee: Kirill Tkalenko
>            Priority: Major
>              Labels: ignite-3
>             Fix For: 3.0.0-beta1
>
>          Time Spent: 3h 50m
>  Remaining Estimate: 0h
>
> In a simple implementation, instead of a *BinaryTuple*, we store its link from the *FreeList* in the key, this is not optimal and we need to inline the *BinaryTuple* in the key, for starters, you can see how to do this in 2.0.
> What should be done:
> * Calculate approximate inline size:
> ** It is set by the user through the configuration or calculated automatically, but should not be more than 2 KB (similar to *PageIO#MAX_PAYLOAD_SIZE* from 2.0);
> ** For automatic calculation, the *BinaryTuple* format must be taken into account: header + null map + offset table;
> *** To cover most cases, we will consider the size class to be 2 bytes ([BinaryTupleFormat-Header|https://cwiki.apache.org/confluence/display/IGNITE/IEP-92%3A+Binary+Tuple+Format#IEP92:BinaryTupleFormat-Header]);
> *** For columns of variable length (for example, a string), we will assume that 10 bytes should be enough;
> * Write *BinaryTuple* as is up to inline size;
> ** If the user *BinaryTuple* is larger than the inline size, then without its transformations (as it is) we will write it according to the inline size (cut it off);
> ** If the user *BinaryTuple* is less than or equal to the inline size, then we will write it as is without writing it to the FreeList;
> *** At the same time, we need to make a note somewhere that the *BinaryTuple* is written in full, this will help us when comparing *BinaryTuple*'s inside the B+tree;
> * Comparing *BinaryTuple*'s at B+tree nodes:
> ** If the *BinaryTuple* in the tree node is completely written, then compare them without loading the *BinaryTuple* by link (since we will not write it to the *FreeList*);
> ** Otherwise, compare *BinaryTuple*'s with loading it by link (we need to do it optimally right away).
> The configuration will most likely be done later, since the user experience for this is not yet clear.



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