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https://issues.apache.org/jira/browse/IGNITE-28892?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Aleksey Plekhanov updated IGNITE-28892:
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Description: Currently, for inner collection views to calculate view size
we must iterate over the view. In H2 engine {{getRowCount()}} method returns
{{sysView.size()}} and iterates over the view in some cases (see
{{SystemViewH2Adapter.getRowCount()}}). H2 can call {{getRowCount()}} to
calculate query cost, it leads to double view iterations. We can override
{{canGetRowCount()}} method for some views to aviod this. (was: Currently, for
inner collection views to view size we must iterate over the view. In H2 engine
{{getRowCount()}} method returns {{sysView.size()}} and iterates over the view
in some cases (see {{SystemViewH2Adapter.getRowCount()}}). H2 can call
{{getRowCount()}} to calculate query cost, it leads to double view iterations.
We can override {{canGetRowCount()}} method for some views to aviod this.)
> Double view iteration for select from system views on H2 engine
> ---------------------------------------------------------------
>
> Key: IGNITE-28892
> URL: https://issues.apache.org/jira/browse/IGNITE-28892
> Project: Ignite
> Issue Type: Improvement
> Reporter: Aleksey Plekhanov
> Priority: Major
>
> Currently, for inner collection views to calculate view size we must iterate
> over the view. In H2 engine {{getRowCount()}} method returns
> {{sysView.size()}} and iterates over the view in some cases (see
> {{SystemViewH2Adapter.getRowCount()}}). H2 can call {{getRowCount()}} to
> calculate query cost, it leads to double view iterations. We can override
> {{canGetRowCount()}} method for some views to aviod this.
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