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Re: MDEV-15813 ... HANDLER READ on a versioned HEAP table


Hi, Alexey!

On May 04, Alexey Botchkov wrote:
> Hi, Sergei, guys.
> This bug iis more like a feature of the HASH indexes.
> And i came upon other 'features' while experimenting.
> Firstly the 'range' queries like
>    HANDLER h READ `PRIMARY` < (5);
> cannot be naturally handled by the HASH keys. Only equality queries
> ...'PRIMARY' = (5); make sence.
> And these 'range' queries just return wrong empty result.
> I'd say we need to fire an error in this case. Do you agree?

Yes. Like "HASH index `PRIMARY` does not support this operation" ?

> Second problem - the SYSTEM VERSIONING.
> It adds an extra column to the key, which makes this key virtually
> useless.  I think for the VERSIONING we should either replace the HASH
> key with the RBTREE, or get the row_end data from the table after
> getting records from the HASH.
> What is your idea how to deal with this?

row_end must be a part of every unique key, because uniqueness of
current data should not be affected by historical, deleted, rows.

In this particular use case, HANDLER is a low level command, it doesn't
see high-level features like versioning. So, for HANDLER row_end is just
a normal key part, should be used as

  HANDLER h READ `PRIMARY` = (5, '2038-01-19 03:14:07.999999');

Chief Architect MariaDB
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