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Reduce repetition in try_process_group_by_unnest and try_process_unnest #11714

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merged 2 commits into from
Jul 31, 2024
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Reduce repetition in try_process_group_by_unnest and try_process_unnest #11714

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85cb444
refactor: process unnest
JasonLi-cn Jul 29, 2024
bf8b09d
pass clippy
JasonLi-cn Jul 29, 2024
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42 changes: 13 additions & 29 deletions datafusion/sql/src/select.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,7 @@ use crate::planner::{
};
use crate::utils::{
check_columns_satisfy_exprs, extract_aliases, rebase_expr, resolve_aliases_to_exprs,
resolve_columns, resolve_positions_to_exprs, transform_bottom_unnest,
resolve_columns, resolve_positions_to_exprs, transform_bottom_unnests,
};

use datafusion_common::tree_node::{TreeNode, TreeNodeRecursion};
Expand Down Expand Up @@ -318,20 +318,12 @@ impl<'a, S: ContextProvider> SqlToRel<'a, S> {
// - unnest(struct_col) will be transformed into unnest(struct_col).field1, unnest(struct_col).field2
// - unnest(array_col) will be transformed into unnest(array_col).element
// - unnest(array_col) + 1 will be transformed into unnest(array_col).element +1
let outer_projection_exprs: Vec<Expr> = intermediate_select_exprs
.iter()
.map(|expr| {
transform_bottom_unnest(
&intermediate_plan,
&mut unnest_columns,
&mut inner_projection_exprs,
expr,
)
})
.collect::<Result<Vec<_>>>()?
.into_iter()
.flatten()
.collect();
let outer_projection_exprs = transform_bottom_unnests(
&intermediate_plan,
&mut unnest_columns,
&mut inner_projection_exprs,
&intermediate_select_exprs,
)?;

// No more unnest is possible
if unnest_columns.is_empty() {
Expand Down Expand Up @@ -417,20 +409,12 @@ impl<'a, S: ContextProvider> SqlToRel<'a, S> {
let mut unnest_columns = vec![];
let mut inner_projection_exprs = vec![];

let outer_projection_exprs: Vec<Expr> = intermediate_select_exprs
.iter()
.map(|expr| {
transform_bottom_unnest(
&intermediate_plan,
&mut unnest_columns,
&mut inner_projection_exprs,
expr,
)
})
.collect::<Result<Vec<_>>>()?
.into_iter()
.flatten()
.collect();
let outer_projection_exprs = transform_bottom_unnests(
&intermediate_plan,
&mut unnest_columns,
&mut inner_projection_exprs,
&intermediate_select_exprs,
)?;

if unnest_columns.is_empty() {
break;
Expand Down
22 changes: 22 additions & 0 deletions datafusion/sql/src/utils.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -287,6 +287,28 @@ pub(crate) fn value_to_string(value: &Value) -> Option<String> {
}
}

pub(crate) fn transform_bottom_unnests(
input: &LogicalPlan,
unnest_placeholder_columns: &mut Vec<String>,
inner_projection_exprs: &mut Vec<Expr>,
original_exprs: &[Expr],
) -> Result<Vec<Expr>> {
Ok(original_exprs
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This does the recursion manually -- I wonder if it would be possible / useful to do the recursion using transform_up from TreeNode: https://docs.rs/datafusion/latest/datafusion/common/tree_node/trait.TreeNode.html#method.transform_up

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Thank you @alamb for your review. I'm not quite sure what you mean, maybe you can add more description, thanks again. 🙏

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I think I was confused -- sorry

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I think we can, in fact transform_up_down is needed, i'll introduce why in this PR when it's ready: #11577

.iter()
.map(|expr| {
transform_bottom_unnest(
input,
unnest_placeholder_columns,
inner_projection_exprs,
expr,
)
})
.collect::<Result<Vec<_>>>()?
.into_iter()
.flatten()
.collect::<Vec<_>>())
}

/// The context is we want to rewrite unnest() into InnerProjection->Unnest->OuterProjection
/// Given an expression which contains unnest expr as one of its children,
/// Try transform depends on unnest type
Expand Down