Vladimir Pligin created IGNITE-22506:
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Summary: Table size can be useful in many ways including SQL
planning. Also users expect to have such an API exposed to them.
Key: IGNITE-22506
URL: https://issues.apache.org/jira/browse/IGNITE-22506
Project: Ignite
Issue Type: Epic
Reporter: Vladimir Pligin
Currently there is no equivalent for `cache.size()`.
The only way to get the size is
{{}}
{code:java}
select count(*) from table {code}
{{{}{}}}And this is a is slow operation as it scans the entire dataset.
Initially we should start by providing an eventually-consistent size
table.sizeEstimate() It needs to be the true size under no load, and it can
kind of show whatever under load. It is NOT a transactional method. We might
even forbid to call it in a transactional context.
For SQL, let's at least make sure that count(*) can execute over the index
without reading the actual data. This would be a useful optimization for many
cases and should give a semi-reasonable performance for both RW and RO.
I think it's also possible to delegate select count(*) from table to
table.sizeEstimate() when it isn't in an explicit transaction.
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