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SNOW-3489991: Block flattening of dropped NEW columns in connect mode #4259

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SNOW-3489991: Block flattening of dropped NEW columns in connect mode #4259

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SNOW-3489991: block flattening of dropped NEW columns in connect mode
sfc-gh-joshi Jun 11, 2026
b1a9a74
SNOW-3489991: replace global connect-mode guard with targeted per-sta…
sfc-gh-joshi Jun 11, 2026
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15 changes: 12 additions & 3 deletions src/snowflake/snowpark/_internal/analyzer/select_statement.py
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Original file line number Diff line number Diff line change
Expand Up @@ -269,6 +269,7 @@ def __init__(
self.pre_actions: Optional[List["Query"]] = None
self.post_actions: Optional[List["Query"]] = None
self.flatten_disabled: bool = False
self.protect_dropped_new_columns: bool = False
self._column_states: Optional[ColumnStateDict] = None
self._snowflake_plan: Optional[SnowflakePlan] = None
self.expr_to_alias = (
Expand Down Expand Up @@ -1499,7 +1500,7 @@ def select(self, cols: List[Expression]) -> "SelectStatement":
can_be_flattened = False
else:
can_be_flattened = can_select_statement_be_flattened(
self.column_states, new_column_states
self.column_states, new_column_states, self.protect_dropped_new_columns
)

if can_be_flattened:
Expand Down Expand Up @@ -2196,7 +2197,9 @@ def parse_column_name(


def can_select_statement_be_flattened(
subquery_column_states: ColumnStateDict, new_column_states: ColumnStateDict
subquery_column_states: ColumnStateDict,
new_column_states: ColumnStateDict,
protect_dropped_new_columns: bool = False,
) -> bool:
for col, state in new_column_states.items():
dependent_columns = state.dependent_columns
Expand All @@ -2219,7 +2222,13 @@ def can_select_statement_be_flattened(
state.change_state == ColumnChangeState.DROPPED
and (subquery_state := subquery_column_states.get(col))
and subquery_state.change_state == ColumnChangeState.NEW
and subquery_state.is_referenced_by_same_level_column
and (
subquery_state.is_referenced_by_same_level_column
# If the subquery was explicitly marked (e.g. by the SCOS withColumn
# path), preserve it so that future filter/sort clauses can still
# reference the dropped NEW column.
or protect_dropped_new_columns
)
):
return False
return True
Expand Down
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