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Raise a plan error on union if column count is not the same between plans #13117

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Merged
jonahgao merged 1 commit into from
Oct 28, 2024
Merged

Raise a plan error on union if column count is not the same between plans #13117

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9 changes: 9 additions & 0 deletions datafusion/expr/src/logical_plan/builder.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1482,6 +1482,15 @@ pub fn validate_unique_names<'a>(
/// [`TypeCoercionRewriter::coerce_union`]: https://docs.rs/datafusion-optimizer/latest/datafusion_optimizer/analyzer/type_coercion/struct.TypeCoercionRewriter.html#method.coerce_union
/// [`coerce_union_schema`]: https://docs.rs/datafusion-optimizer/latest/datafusion_optimizer/analyzer/type_coercion/fn.coerce_union_schema.html
pub fn union(left_plan: LogicalPlan, right_plan: LogicalPlan) -> Result<LogicalPlan> {
if left_plan.schema().fields().len() != right_plan.schema().fields().len() {
return plan_err!(
"UNION queries have different number of columns: \
left has {} columns whereas right has {} columns",
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@findepi findepi Oct 26, 2024

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This is good check to have. 👍

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@alamb alamb Oct 26, 2024

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👍 I agree -- it is an easy check to add that can catch clearly incorrect plans (though as @findepi notes it won't catch all issues)

left_plan.schema().fields().len(),
right_plan.schema().fields().len()
);
}

// Temporarily use the schema from the left input and later rely on the analyzer to
// coerce the two schemas into a common one.

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4 changes: 2 additions & 2 deletions datafusion/sqllogictest/test_files/type_coercion.slt
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Expand Up @@ -103,11 +103,11 @@ CREATE TABLE orders(
);

# union_different_num_columns_error() / UNION
query error Error during planning: Union schemas have different number of fields: query 1 has 1 fields whereas query 2 has 2 fields
query error DataFusion error: Error during planning: UNION queries have different number of columns: left has 1 columns whereas right has 2 columns
SELECT order_id FROM orders UNION SELECT customer_id, o_item_id FROM orders

# union_different_num_columns_error() / UNION ALL
query error Error during planning: Union schemas have different number of fields: query 1 has 1 fields whereas query 2 has 2 fields
query error DataFusion error: Error during planning: UNION queries have different number of columns: left has 1 columns whereas right has 2 columns
SELECT order_id FROM orders UNION ALL SELECT customer_id, o_item_id FROM orders

# union_with_different_column_names()
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