Vladimir Ozerov created IGNITE-8385:
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Summary: SQL: allow variable-length values in index leafs
Key: IGNITE-8385
URL: https://issues.apache.org/jira/browse/IGNITE-8385
Project: Ignite
Issue Type: Task
Components: sql
Affects Versions: 2.4
Reporter: Vladimir Ozerov
Fix For: 2.6
Currently we have a restriction that every entry inside a BTree leaf should be
of fixed size. This restriction is artificial and prevents efficient index
usage because we have to choose so-called {{inline size}} for every index
manually. This is OK for fixed-size numeric types. But this could be a problem
for varlen types such as {{VARCHAR}} because in some cases we cannot fit the
whole value and have to fallback to data page lookup. In other cases we may
pick too pessimistic inline size value and index space would be wasted.
What we need to do is to allow arbitrary item size in index pages. In this case
we would be able to inline all necessary values into index pages in most cases.
Please pay attention that we may still met page overflow in case too long data
types are used. To mitigate this we should:
1) Implement IGNITE-6055 first so that we can distinguish between limited and
unlimited data types.
2) Unlimited data types should be inlined only partially
3) We need to have special handling for too long rows (probably just re-use
existing logic with minimal adjustments)
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