Module partition_compat 

Preflight validation of persisted partition expressions against an ALTER TABLE schema change.

Persisted partition bounds keep the types they were written with. A column whose type changes while a partition expression references it breaks the region on both paths that consume the bounds:

• On scan, the region coerces the bound literal and the new column type to a common comparison type while building the partition predicate. If no common type exists, or the bound cannot be cast to it (a classic example is a millisecond timestamp bound that overflows when the time index column is widened to nanoseconds), every scan of that region fails at that point.
• On write, the region routes rows through MultiDimPartitionRule::find_region, which compares the persisted bound against row values directly (Value::cmp): a bound whose variant no longer matches the column’s panics on ordered comparisons and misroutes silently on equality. Only a timestamp unit widening keeps the two comparable — Timestamp comparisons convert units before comparing — so every other type change of a referenced column is rejected outright, and the widening keeps the scan check below.

Such an ALTER must be rejected before it is submitted to any region, otherwise already-altered regions keep failing while the rest of the table is untouched.

The partition crate depends on common-meta, so this crate cannot depend on partition back and cannot reuse [partition::expr::PartitionExpr]. The Persisted* types below mirror the JSON representation of partition::partition::PartitionBound and partition::expr::PartitionExpr and must be kept in sync with partition/src/partition.rs and partition/src/expr.rs; round-trip tests in partition run real serialized expressions through this validator so drift fails in CI. The compatibility check itself deliberately repeats the same conversion (value -> [ScalarValue]) and the same comparison coercion the region performs when it builds the partition predicate (ExprSimplifier::coerce / [comparison_coercion]): both sides are cast to the common comparison type, and the persisted bound must be castable to that type with [ScalarValue::cast_to]. A bound that would fail on scan is rejected here as well.

Structs

PersistedPartitionExpr 🔒

Mirrors partition::expr::PartitionExpr.

Enums

PersistedOp 🔒

Mirrors partition::expr::RestrictedOp.

PersistedOperand 🔒

Mirrors partition::expr::Operand.

PersistedPartitionBound 🔒

Mirrors partition::partition::PartitionBound.

Functions

changed_column_types 🔒

Returns the columns whose data type differs between old_schema and new_schema, mapped to (old type, new type). Columns only present in one of the schemas (added or dropped) are not included; dropping a column referenced by a partition expression is already rejected by the table metadata validation.

validate_comparison 🔒

validate_expr 🔒

validate_operand 🔒

validate_region_partition_bounds

Validates that the persisted partition bounds of every region are still representable with the types of changed_columns. Returns an error naming the first offending region without modifying anything.

value_to_scalar_value 🔒

Converts a persisted bound value to a [ScalarValue], mirroring partition::expr::Operand::try_as_logical_expr. Returns None for values that cannot appear in a persisted partition expression.