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Posted to github@arrow.apache.org by "mustafasrepo (via GitHub)" <gi...@apache.org> on 2023/06/14 12:21:48 UTC

[GitHub] [arrow-datafusion] mustafasrepo opened a new pull request, #6665: Combine evaluate_stateful and evaluate_inside_range

mustafasrepo opened a new pull request, #6665:
URL: https://github.com/apache/arrow-datafusion/pull/6665

   # Which issue does this PR close?
   
   <!--
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   Closes #.
   
   # Rationale for this change
   
   <!--
    Why are you proposing this change? If this is already explained clearly in the issue then this section is not needed.
    Explaining clearly why changes are proposed helps reviewers understand your changes and offer better suggestions for fixes.  
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   # What changes are included in this PR?
   This PR implements the proposal in the [#PR12](https://github.com/alamb/arrow-datafusion/pull/12)
   - `evaluate_stateful` and `evaluate_inside_range` are combined under single `evaluate` methods
   - `uses_window_frame` and `supports_bounded_execution` methods are moved from `BoundedWindowFunctionExpr` to `PartitionEvaluator`.
   
   With the changes in this PR new Evaluators can be implemented according to table below.
   |uses_window_frame|supports_bounded_execution|function_to_implement|
   |---|---|----|
   |false|false|`evaluate_all` (if we were to implement `PERCENT_RANK` it would end up in this quadrant, we cannot produce any result without seeing whole data)|
   |false|true|`evaluate` (optionally can also implement `evaluate_all` for more optimized implementation. However, there will be default implementation that is suboptimal) . If we were to implement `ROW_NUMBER` it will end up in this quadrant. Example `OddRowNumber` showcases this use case|
   |true|false|`evaluate` (I think as long as `uses_window_frame` is `true`. There is no way for `supports_bounded_execution` to be false). I couldn't come up with any example for this quadrant |
   |true|true|`evaluate`. If we were to implement `FIRST_VALUE`, it would end up in this quadrant|.
   
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[GitHub] [arrow-datafusion] mustafasrepo commented on a diff in pull request #6665: Combine evaluate_stateful and evaluate_inside_range

Posted by "mustafasrepo (via GitHub)" <gi...@apache.org>.
mustafasrepo commented on code in PR #6665:
URL: https://github.com/apache/arrow-datafusion/pull/6665#discussion_r1229645276


##########
datafusion/physical-expr/src/window/built_in_window_function_expr.rs:
##########
@@ -86,27 +86,10 @@ pub trait BuiltInWindowFunctionExpr: Send + Sync + std::fmt::Debug {
     /// The default implementation does nothing
     fn add_equal_orderings(&self, _builder: &mut OrderingEquivalenceBuilder) {}
 
-    /// Can the window function be incrementally computed using
-    /// bounded memory?
-    ///
-    /// If this function returns true, [`Self::create_evaluator`] must
-    /// implement [`PartitionEvaluator::evaluate_stateful`]
-    fn supports_bounded_execution(&self) -> bool {
-        false
-    }
-
-    /// Does the window function use the values from its window frame?
-    ///
-    /// If this function returns true, [`Self::create_evaluator`] must
-    /// implement [`PartitionEvaluator::evaluate_inside_range`]
-    fn uses_window_frame(&self) -> bool {
-        false
-    }
-
     /// Can this function be evaluated with (only) rank
     ///
     /// If `include_rank` is true, then [`Self::create_evaluator`] must
-    /// implement [`PartitionEvaluator::evaluate_with_rank`]
+    /// implement [`PartitionEvaluator::evaluate_with_rank_all`]

Review Comment:
   For consistency, I have moved `include_rank` flag to `PartitionEvaluator` also.



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[GitHub] [arrow-datafusion] alamb merged pull request #6665: Combine evaluate_stateful and evaluate_inside_range

Posted by "alamb (via GitHub)" <gi...@apache.org>.
alamb merged PR #6665:
URL: https://github.com/apache/arrow-datafusion/pull/6665


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[GitHub] [arrow-datafusion] alamb commented on a diff in pull request #6665: Combine evaluate_stateful and evaluate_inside_range

Posted by "alamb (via GitHub)" <gi...@apache.org>.
alamb commented on code in PR #6665:
URL: https://github.com/apache/arrow-datafusion/pull/6665#discussion_r1230106114


##########
datafusion/physical-expr/src/window/rank.rs:
##########
@@ -115,12 +115,6 @@ pub(crate) struct RankEvaluator {
 }
 
 impl PartitionEvaluator for RankEvaluator {
-    fn get_range(&self, idx: usize, _n_rows: usize) -> Result<Range<usize>> {

Review Comment:
   ❤️ 



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[GitHub] [arrow-datafusion] alamb commented on a diff in pull request #6665: Combine evaluate_stateful and evaluate_inside_range

Posted by "alamb (via GitHub)" <gi...@apache.org>.
alamb commented on code in PR #6665:
URL: https://github.com/apache/arrow-datafusion/pull/6665#discussion_r1229589764


##########
datafusion/physical-expr/src/window/built_in_window_function_expr.rs:
##########
@@ -86,27 +86,10 @@ pub trait BuiltInWindowFunctionExpr: Send + Sync + std::fmt::Debug {
     /// The default implementation does nothing
     fn add_equal_orderings(&self, _builder: &mut OrderingEquivalenceBuilder) {}
 
-    /// Can the window function be incrementally computed using
-    /// bounded memory?
-    ///
-    /// If this function returns true, [`Self::create_evaluator`] must
-    /// implement [`PartitionEvaluator::evaluate_stateful`]
-    fn supports_bounded_execution(&self) -> bool {
-        false
-    }
-
-    /// Does the window function use the values from its window frame?
-    ///
-    /// If this function returns true, [`Self::create_evaluator`] must
-    /// implement [`PartitionEvaluator::evaluate_inside_range`]
-    fn uses_window_frame(&self) -> bool {
-        false
-    }
-
     /// Can this function be evaluated with (only) rank
     ///
     /// If `include_rank` is true, then [`Self::create_evaluator`] must
-    /// implement [`PartitionEvaluator::evaluate_with_rank`]
+    /// implement [`PartitionEvaluator::evaluate_with_rank_all`]

Review Comment:
   Do you plan to give the same treatment (move to `PartitionEvaluator`) to `include_rank`?



##########
datafusion/physical-expr/src/window/partition_evaluator.rs:
##########
@@ -132,23 +140,40 @@ pub trait PartitionEvaluator: Debug + Send {
 
     /// Called for window functions that *do not use* values from the
     /// the window frame, such as `ROW_NUMBER`, `RANK`, `DENSE_RANK`,
-    /// `PERCENT_RANK`, `CUME_DIST`, `LEAD`, `LAG`).
-    fn evaluate(&self, _values: &[ArrayRef], _num_rows: usize) -> Result<ArrayRef> {
-        Err(DataFusionError::NotImplemented(
-            "evaluate is not implemented by default".into(),
-        ))
+    /// `PERCENT_RANK`, `CUME_DIST`, `LEAD`, `LAG`). It produces result
+    /// of all rows in a single pass. It expects to receive whole table data
+    /// as a single batch.
+    fn evaluate_all(&mut self, values: &[ArrayRef], num_rows: usize) -> Result<ArrayRef> {
+        // When window frame boundaries are not used and evaluator supports bounded execution
+        // We can calculate evaluate result by repeatedly calling `self.evaluate` `num_rows` times
+        // If user wants to implement more efficient version, this method should be overwritten
+        // Default implementation may behave suboptimally (For instance `NumRowEvaluator` overwrites it)
+        if !self.uses_window_frame() && self.supports_bounded_execution() {
+            let res = (0..num_rows)
+                .map(|_idx| self.evaluate(values, &Range { start: 0, end: 1 }))
+                .collect::<Result<Vec<_>>>()?;
+            ScalarValue::iter_to_array(res.into_iter())
+        } else {
+            Err(DataFusionError::NotImplemented(
+                "evaluate_all is not implemented by default".into(),

Review Comment:
   ```suggestion
                   format!("evaluate_all is not implemented for {} when using window frames", self.name()),
   ```
   
   I think the error could be more helpful, but I can also add that as a follow on PR
   



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[GitHub] [arrow-datafusion] mustafasrepo commented on a diff in pull request #6665: Combine evaluate_stateful and evaluate_inside_range

Posted by "mustafasrepo (via GitHub)" <gi...@apache.org>.
mustafasrepo commented on code in PR #6665:
URL: https://github.com/apache/arrow-datafusion/pull/6665#discussion_r1229614204


##########
datafusion/physical-expr/src/window/built_in_window_function_expr.rs:
##########
@@ -86,27 +86,10 @@ pub trait BuiltInWindowFunctionExpr: Send + Sync + std::fmt::Debug {
     /// The default implementation does nothing
     fn add_equal_orderings(&self, _builder: &mut OrderingEquivalenceBuilder) {}
 
-    /// Can the window function be incrementally computed using
-    /// bounded memory?
-    ///
-    /// If this function returns true, [`Self::create_evaluator`] must
-    /// implement [`PartitionEvaluator::evaluate_stateful`]
-    fn supports_bounded_execution(&self) -> bool {
-        false
-    }
-
-    /// Does the window function use the values from its window frame?
-    ///
-    /// If this function returns true, [`Self::create_evaluator`] must
-    /// implement [`PartitionEvaluator::evaluate_inside_range`]
-    fn uses_window_frame(&self) -> bool {
-        false
-    }
-
     /// Can this function be evaluated with (only) rank
     ///
     /// If `include_rank` is true, then [`Self::create_evaluator`] must
-    /// implement [`PartitionEvaluator::evaluate_with_rank`]
+    /// implement [`PartitionEvaluator::evaluate_with_rank_all`]

Review Comment:
   We can do so, what do you think about it. Should we do that?



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[GitHub] [arrow-datafusion] mustafasrepo commented on a diff in pull request #6665: Combine evaluate_stateful and evaluate_inside_range

Posted by "mustafasrepo (via GitHub)" <gi...@apache.org>.
mustafasrepo commented on code in PR #6665:
URL: https://github.com/apache/arrow-datafusion/pull/6665#discussion_r1229614204


##########
datafusion/physical-expr/src/window/built_in_window_function_expr.rs:
##########
@@ -86,27 +86,10 @@ pub trait BuiltInWindowFunctionExpr: Send + Sync + std::fmt::Debug {
     /// The default implementation does nothing
     fn add_equal_orderings(&self, _builder: &mut OrderingEquivalenceBuilder) {}
 
-    /// Can the window function be incrementally computed using
-    /// bounded memory?
-    ///
-    /// If this function returns true, [`Self::create_evaluator`] must
-    /// implement [`PartitionEvaluator::evaluate_stateful`]
-    fn supports_bounded_execution(&self) -> bool {
-        false
-    }
-
-    /// Does the window function use the values from its window frame?
-    ///
-    /// If this function returns true, [`Self::create_evaluator`] must
-    /// implement [`PartitionEvaluator::evaluate_inside_range`]
-    fn uses_window_frame(&self) -> bool {
-        false
-    }
-
     /// Can this function be evaluated with (only) rank
     ///
     /// If `include_rank` is true, then [`Self::create_evaluator`] must
-    /// implement [`PartitionEvaluator::evaluate_with_rank`]
+    /// implement [`PartitionEvaluator::evaluate_with_rank_all`]

Review Comment:
   We can do so, what do you think about it?



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