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fix: Consider column names' case when aliasing tables #22917

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Merged
kosiew merged 7 commits into from
Jun 22, 2026
Merged

fix: Consider column names' case when aliasing tables #22917

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b19e42f
fix: Consider column names' case when aliasing tables
nuno-faria Jun 11, 2026
edf4ef8
Use from_qualified_name_ignore_case directly in apply_expr_alias
nuno-faria Jun 11, 2026
02eebf4
Alias the existing columns instead
nuno-faria Jun 18, 2026
8521012
Merge branch 'main' into fix_alias_case_sensitive
nuno-faria Jun 18, 2026
4934e8a
Fix fmt
nuno-faria Jun 18, 2026
68509dd
Merge branch 'fix_alias_case_sensitive' of https://github.com/nuno-fa…
nuno-faria Jun 18, 2026
644c14c
Merge branch 'main' into fix_alias_case_sensitive
nuno-faria Jun 20, 2026
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7 changes: 4 additions & 3 deletions datafusion/sql/src/planner.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -23,19 +23,19 @@ use std::vec;

use crate::utils::make_decimal_type;
use arrow::datatypes::*;
use datafusion_common::TableReference;
use datafusion_common::config::SqlParserOptions;
use datafusion_common::datatype::{DataTypeExt, FieldExt};
use datafusion_common::error::add_possible_columns_to_diag;
use datafusion_common::{Column, TableReference};
use datafusion_common::{DFSchema, DataFusionError, Result, not_impl_err, plan_err};
use datafusion_common::{
DFSchemaRef, Diagnostic, SchemaError, field_not_found, internal_err,
plan_datafusion_err,
};
use datafusion_expr::Expr;
use datafusion_expr::logical_plan::{LogicalPlan, LogicalPlanBuilder};
pub use datafusion_expr::planner::ContextProvider;
use datafusion_expr::utils::find_column_exprs;
use datafusion_expr::{Expr, col};
use sqlparser::ast::{ArrayElemTypeDef, ExactNumberInfo, TimezoneInfo};
use sqlparser::ast::{ColumnDef as SQLColumnDef, ColumnOption};
use sqlparser::ast::{DataType as SQLDataType, Ident, ObjectName, TableAlias};
Expand Down Expand Up @@ -575,7 +575,8 @@ impl<'a, S: ContextProvider> SqlToRel<'a, S> {
let fields = plan.schema().fields().clone();
LogicalPlanBuilder::from(plan)
.project(fields.iter().zip(idents).map(|(field, ident)| {
col(field.name()).alias(self.ident_normalizer.normalize(ident))
Expr::Column(Column::from_qualified_name_ignore_case(field.name()))

@kosiew kosiew Jun 17, 2026

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apply_expr_alias still rebuilds a column reference by reparsing field.name() as SQL text. That helps with the simple case-sensitive name case, but quoted identifiers can legally contain separators like ..

For example, CREATE TABLE t ("A.B" int); SELECT * FROM (SELECT * FROM t) t_(x); is still resolved as a qualified column A.B instead of the existing field named A.B, so aliasing still errors.

I think the important invariant here is positional: each existing output field should be aliased while preserving its already resolved schema identity. Could we build Expr::Column from plan.schema().columns() or qualified_field instead of parsing the display name string? One way to do that would be to collect the schema columns before moving plan, then zip those with idents.

@nuno-faria nuno-faria Jun 18, 2026

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Thanks @kosiew, it's better to alias the existing columns directly. I also updated the test to include a column with a dot.

.alias(self.ident_normalizer.normalize(ident))
}))?
.build()
}
Expand Down
47 changes: 47 additions & 0 deletions datafusion/sqllogictest/test_files/alias.slt
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Expand Up @@ -57,3 +57,50 @@ drop table t1;

statement count 0
drop table t2;


# Test table-aliasing a subquery with a case sensitive column
# (https://github.com/apache/datafusion/issues/22916)

statement ok
create table t ("A" int);

query I
select * from (select * from t) t_(x);
----

query TT
explain select * from (select * from t) t_(x);
----
logical_plan
01)SubqueryAlias: t_
02)--Projection: t.A AS x
03)----TableScan: t projection=[A]
physical_plan
01)ProjectionExec: expr=[A@0 as x]
02)--DataSourceExec: partitions=1, partition_sizes=[0]

query TT
explain select * from (select * from t) t_(X);
----
logical_plan
01)SubqueryAlias: t_
02)--Projection: t.A AS x
03)----TableScan: t projection=[A]
physical_plan
01)ProjectionExec: expr=[A@0 as x]
02)--DataSourceExec: partitions=1, partition_sizes=[0]

query TT
explain select * from (select * from t) t_("X");
----
logical_plan
01)SubqueryAlias: t_
02)--Projection: t.A AS X
03)----TableScan: t projection=[A]
physical_plan
01)ProjectionExec: expr=[A@0 as X]
02)--DataSourceExec: partitions=1, partition_sizes=[0]

statement ok
drop table t;
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