returnString commented on a change in pull request #8917:
URL: https://github.com/apache/arrow/pull/8917#discussion_r543494569
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File path: rust/datafusion/src/datasource/datasource.rs
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@@ -34,6 +35,23 @@ pub struct Statistics {
pub total_byte_size: Option<usize>,
}
+/// Indicates whether and how a filter expression can be handled by a
+/// TableProvider for table scans.
+#[derive(Debug, Clone)]
+pub enum TableProviderFilterPushDown {
+ /// The expression cannot be used by the provider.
+ Unsupported,
+ /// The expression can be used to help minimise the data retrieved,
+ /// but the provider cannot guarantee that all returned tuples
Review comment:
This result is used to drive the logical plan optimisation. Returning
`Unsupported` _or_ `Inexact` will both result in the original filter node being
preserved in the plan (only `Exact` can provide optimisation guarantees that
the post-hoc filtering is unecessary) but `Inexact` means that the filter expr
in question will be passed to `TableProvider::scan` when creating the execution
plan, whereas `Unsupported` means the provider can do nothing useful with the
expr at all (relevant code is
[here](https://github.com/apache/arrow/pull/8917/files#diff-5f6ab9edcef3a4b9a8eb75f641ac0930cdbae92156f056fea400e0c58218a094R354-R369)).
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