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https://issues.apache.org/jira/browse/CALCITE-5649?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17712589#comment-17712589
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Adam Kennedy commented on CALCITE-5649:
---------------------------------------
https://github.com/apache/calcite/pull/3154
This PR adds support for row count statistics for simple array cases, and a
test to validate the row count is returned.
> Produce row count statistics from ReflectiveSchema for array based tables
> -------------------------------------------------------------------------
>
> Key: CALCITE-5649
> URL: https://issues.apache.org/jira/browse/CALCITE-5649
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.34.0
> Reporter: Adam Kennedy
> Priority: Minor
> Labels: pull-request-available
> Time Spent: 10m
> Remaining Estimate: 0h
>
> When testing new Calcite implementations it is easy to use (and several
> online examples indeed use) a trivial reflected synthetic schema such as the
> following:
> {code:java}
> public Schema getSchema() {
> return new ReflectiveSchema(new PeopleSchema());
> }
> public static final class PeopleSchema {
> public final Person[] heroes = {
> new Person("Ironman", 12),
> new Person("Batman", 10)
> };
> public static class Person {
> public final String name;
> public final int age;
> public Person(final String name, final int age) {
> this.name = name;
> this.age = age;
> }
> }
> }
> {code}
> While this works for some basics, the lack of statistics makes it less useful
> than it could be. While not all variations supported by ReflectiveSchema can
> easily capture statistics, the variation which provides the table as an array
> has trivial access to a valid RowCount value.
> For these simple cases ReflectiveSchema should provide a Statistic object
> with a valid row count so the simple synthetic schemas will be more useful.
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