nseekhao commented on code in PR #14194:
URL: https://github.com/apache/datafusion/pull/14194#discussion_r1975616391
##########
datafusion/substrait/src/logical_plan/producer.rs:
##########
@@ -559,12 +559,31 @@ pub fn from_table_scan(
let table_schema = scan.source.schema().to_dfschema_ref()?;
let base_schema = to_substrait_named_struct(&table_schema)?;
+ let best_effort_filter_option = if !scan.filters.is_empty() {
+ let table_schema_qualified = Arc::new(
+ DFSchema::try_from_qualified_schema(
+ scan.table_name.clone(),
+ &(scan.source.schema()),
+ )
+ .unwrap(),
+ );
+ let mut combined_expr = scan.filters[0].clone();
+ for i in 1..scan.filters.len() {
+ combined_expr = combined_expr.and(scan.filters[i].clone());
+ }
+ let best_effort_filter_expr =
+ producer.handle_expr(&combined_expr, &table_schema_qualified)?;
+ Some(Box::new(best_effort_filter_expr))
+ } else {
+ None
+ };
+
Ok(Box::new(Rel {
rel_type: Some(RelType::Read(Box::new(ReadRel {
common: None,
base_schema: Some(base_schema),
filter: None,
- best_effort_filter: None,
+ best_effort_filter: best_effort_filter_option,
Review Comment:
Thanks @westonpace ! Makes sense, but let me make sure my understanding is
correct.
So let's say we have
```sql
select c2 from t1 where c1 > 0;
```
The logical plan will look something like:
```
Projection:
expr: c1
Filter:
predicate: (c1 > 0)
TableScan:
table_name: t1
filters: None
...
```
During logical plan optimization, the predicate from `Filter` will get
pushed down to `TableScan`. Let's say data is partitioned and metadata contains
ranges of `c1`. Since we could have partitions that contain both positive and
negative `c1` values, my understanding is that the filter will be `Inexact` to
make sure the physical plan knows to keep the original `FilterExec`. So the
logical plan will look something like:
```
Projection:
expr: c1
Filter:
predicate: (c1 > 0)
TableScan:
table_name: t1
filters: [(c1>0, Inexact)]
...
```
So the logical `TableScan` is saying:
* "The filter `c1 > 0` has to be applied" -- communicated via
`TableScan#filters` containing `c1 > 0` expression
* "But I cannot be sure that I won't get in extra rows due to how the data
is partitioned" -- communicated via `Inexact`
* "So please make sure the filter relation that asked for this condition
stays when we translate this logical plan to physical plan. To ensure the
correct results" -- communicated via `Inexact`
Is this a correct understanding?
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