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minor: Refactor some unparser methods to improve readability #10788

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Merged
alamb merged 1 commit into from
Jun 4, 2024
Merged

minor: Refactor some unparser methods to improve readability #10788

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152 changes: 83 additions & 69 deletions datafusion/sql/src/unparser/plan.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,7 @@

use datafusion_common::{internal_err, not_impl_err, plan_err, DataFusionError, Result};
use datafusion_expr::{
expr::Alias, Distinct, Expr, JoinConstraint, JoinType, LogicalPlan,
expr::Alias, Distinct, Expr, JoinConstraint, JoinType, LogicalPlan, Projection,
};
use sqlparser::ast::{self, SetExpr};

Expand Down Expand Up @@ -131,6 +131,87 @@ impl Unparser<'_> {
Ok(ast::SetExpr::Select(Box::new(select_builder.build()?)))
}

/// Reconstructs a SELECT SQL statement from a logical plan by unprojecting column expressions
/// found in a [Projection] node. This requires scanning the plan tree for relevant Aggregate
/// and Window nodes and matching column expressions to the appropriate agg or window expressions.
fn reconstruct_select_statement(
&self,
plan: &LogicalPlan,
p: &Projection,
select: &mut SelectBuilder,
) -> Result<()> {
match find_agg_node_within_select(plan, None, true) {
Some(AggVariant::Aggregate(agg)) => {
let items = p
.expr
.iter()
.map(|proj_expr| {
let unproj = unproject_agg_exprs(proj_expr, agg)?;
self.select_item_to_sql(&unproj)
})
.collect::<Result<Vec<_>>>()?;

select.projection(items);
select.group_by(ast::GroupByExpr::Expressions(
agg.group_expr
.iter()
.map(|expr| self.expr_to_sql(expr))
.collect::<Result<Vec<_>>>()?,
));
}
Some(AggVariant::Window(window)) => {
let items = p
.expr
.iter()
.map(|proj_expr| {
let unproj = unproject_window_exprs(proj_expr, &window)?;
self.select_item_to_sql(&unproj)
})
.collect::<Result<Vec<_>>>()?;

select.projection(items);
}
None => {
let items = p
.expr
.iter()
.map(|e| self.select_item_to_sql(e))
.collect::<Result<Vec<_>>>()?;
select.projection(items);
}
}
Ok(())
}

fn projection_to_sql(
&self,
plan: &LogicalPlan,
p: &Projection,
query: &mut Option<QueryBuilder>,
select: &mut SelectBuilder,
relation: &mut RelationBuilder,
) -> Result<()> {
// A second projection implies a derived tablefactor
if !select.already_projected() {
self.reconstruct_select_statement(plan, p, select)?;
self.select_to_sql_recursively(p.input.as_ref(), query, select, relation)
} else {
let mut derived_builder = DerivedRelationBuilder::default();
derived_builder.lateral(false).alias(None).subquery({
let inner_statment = self.plan_to_sql(plan)?;
if let ast::Statement::Query(inner_query) = inner_statment {
inner_query
} else {
return internal_err!(
"Subquery must be a Query, but found {inner_statment:?}"
);
}
});
relation.derived(derived_builder);
Ok(())
}
}

fn select_to_sql_recursively(
&self,
plan: &LogicalPlan,
Expand Down Expand Up @@ -159,74 +240,7 @@ impl Unparser<'_> {
Ok(())
}
LogicalPlan::Projection(p) => {
// A second projection implies a derived tablefactor
if !select.already_projected() {
// Special handling when projecting an agregation plan
if let Some(aggvariant) =
find_agg_node_within_select(plan, None, true)
{
match aggvariant {
AggVariant::Aggregate(agg) => {
let items = p
.expr
.iter()
.map(|proj_expr| {
let unproj = unproject_agg_exprs(proj_expr, agg)?;
self.select_item_to_sql(&unproj)
})
.collect::<Result<Vec<_>>>()?;

select.projection(items);
select.group_by(ast::GroupByExpr::Expressions(
agg.group_expr
.iter()
.map(|expr| self.expr_to_sql(expr))
.collect::<Result<Vec<_>>>()?,
));
}
AggVariant::Window(window) => {
let items = p
.expr
.iter()
.map(|proj_expr| {
let unproj =
unproject_window_exprs(proj_expr, &window)?;
self.select_item_to_sql(&unproj)
})
.collect::<Result<Vec<_>>>()?;

select.projection(items);
}
}
} else {
let items = p
.expr
.iter()
.map(|e| self.select_item_to_sql(e))
.collect::<Result<Vec<_>>>()?;
select.projection(items);
}
self.select_to_sql_recursively(
p.input.as_ref(),
query,
select,
relation,
)
} else {
let mut derived_builder = DerivedRelationBuilder::default();
derived_builder.lateral(false).alias(None).subquery({
let inner_statment = self.plan_to_sql(plan)?;
if let ast::Statement::Query(inner_query) = inner_statment {
inner_query
} else {
return internal_err!(
"Subquery must be a Query, but found {inner_statment:?}"
);
}
});
relation.derived(derived_builder);
Ok(())
}
self.projection_to_sql(plan, p, query, select, relation)
}
LogicalPlan::Filter(filter) => {
if let Some(AggVariant::Aggregate(agg)) =
Expand Down
37 changes: 19 additions & 18 deletions datafusion/sql/src/unparser/utils.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -46,29 +46,30 @@ pub(crate) fn find_agg_node_within_select<'a>(
} else {
input.first()?
};

// Agg nodes explicitly return immediately with a single node
// Window nodes accumulate in a vec until encountering a TableScan or 2nd projection
if let LogicalPlan::Aggregate(agg) = input {
Some(AggVariant::Aggregate(agg))
} else if let LogicalPlan::Window(window) = input {
prev_windows = match &mut prev_windows {
Some(AggVariant::Window(windows)) => {
windows.push(window);
match input {
LogicalPlan::Aggregate(agg) => Some(AggVariant::Aggregate(agg)),
LogicalPlan::Window(window) => {
prev_windows = match &mut prev_windows {
Some(AggVariant::Window(windows)) => {
windows.push(window);
prev_windows
}
_ => Some(AggVariant::Window(vec![window])),
};
find_agg_node_within_select(input, prev_windows, already_projected)
}
LogicalPlan::Projection(_) => {
if already_projected {
prev_windows
} else {
find_agg_node_within_select(input, prev_windows, true)
}
_ => Some(AggVariant::Window(vec![window])),
};
find_agg_node_within_select(input, prev_windows, already_projected)
} else if let LogicalPlan::TableScan(_) = input {
prev_windows
} else if let LogicalPlan::Projection(_) = input {
if already_projected {
prev_windows
} else {
find_agg_node_within_select(input, prev_windows, true)
}
} else {
find_agg_node_within_select(input, prev_windows, already_projected)
LogicalPlan::TableScan(_) => prev_windows,
_ => find_agg_node_within_select(input, prev_windows, already_projected),
}
}

Expand Down