Struct CaseExpr 

pub struct CaseExpr {
    body: CaseBody,
    eval_method: EvalMethod,
}

The CASE expression is similar to a series of nested if/else and there are two forms that can be used. The first form consists of a series of boolean “when” expressions with corresponding “then” expressions, and an optional “else” expression.

CASE WHEN condition THEN result [WHEN …] [ELSE result] END

The second form uses a base expression and then a series of “when” clauses that match on a literal value.

CASE expression WHEN value THEN result [WHEN …] [ELSE result] END

Fields

body: CaseBody

The case expression body

eval_method: EvalMethod

Evaluation method to use

Implementations

impl CaseExpr

pub fn try_new( expr: Option<Arc<dyn PhysicalExpr>>, when_then_expr: Vec<(Arc<dyn PhysicalExpr>, Arc<dyn PhysicalExpr>)>, else_expr: Option<Arc<dyn PhysicalExpr>>, ) -> Result<Self>

Create a new CASE WHEN expression

pub fn expr(&self) -> Option<&Arc<dyn PhysicalExpr>>

Optional base expression that can be compared to literal values in the “when” expressions

pub fn when_then_expr( &self, ) -> &[(Arc<dyn PhysicalExpr>, Arc<dyn PhysicalExpr>)]

One or more when/then expressions

pub fn else_expr(&self) -> Option<&Arc<dyn PhysicalExpr>>

Optional “else” expression

impl CaseExpr

fn case_when_with_expr( &self, batch: &RecordBatch, projected: &ProjectedCaseBody, ) -> Result<ColumnarValue>

This function evaluates the form of CASE that matches an expression to fixed values.

CASE expression WHEN value THEN result [WHEN …] [ELSE result] END

fn case_when_no_expr( &self, batch: &RecordBatch, projected: &ProjectedCaseBody, ) -> Result<ColumnarValue>

This function evaluates the form of CASE where each WHEN expression is a boolean expression.

CASE WHEN condition THEN result [WHEN …] [ELSE result] END

fn case_column_or_null(&self, batch: &RecordBatch) -> Result<ColumnarValue>

This function evaluates the specialized case of:

CASE WHEN condition THEN column [ELSE NULL] END

Note that this function is only safe to use for “then” expressions that are infallible because the expression will be evaluated for all rows in the input batch.

fn scalar_or_scalar(&self, batch: &RecordBatch) -> Result<ColumnarValue>

fn expr_or_expr( &self, batch: &RecordBatch, projected: &ProjectedCaseBody, ) -> Result<ColumnarValue>

Trait Implementations

impl Debug for CaseExpr

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for CaseExpr

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Hash for CaseExpr

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for CaseExpr

fn eq(&self, other: &CaseExpr) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PhysicalExpr for CaseExpr

fn as_any(&self) -> &dyn Any

Return a reference to Any that can be used for down-casting

fn data_type(&self, input_schema: &Schema) -> Result<DataType>

Get the data type of this expression, given the schema of the input

fn nullable(&self, input_schema: &Schema) -> Result<bool>

Determine whether this expression is nullable, given the schema of the input

fn evaluate(&self, batch: &RecordBatch) -> Result<ColumnarValue>

Evaluate an expression against a RecordBatch

fn children(&self) -> Vec<&Arc<dyn PhysicalExpr>>

Get a list of child PhysicalExpr that provide the input for this expr.

fn with_new_children( self: Arc<Self>, children: Vec<Arc<dyn PhysicalExpr>>, ) -> Result<Arc<dyn PhysicalExpr>>

Returns a new PhysicalExpr where all children were replaced by new exprs.

fn fmt_sql(&self, f: &mut Formatter<'_>) -> Result

Format this PhysicalExpr in nice human readable “SQL” format

fn return_field( &self, input_schema: &Schema, ) -> Result<Arc<Field>, DataFusionError>

The output field associated with this expression

fn evaluate_selection( &self, batch: &RecordBatch, selection: &BooleanArray, ) -> Result<ColumnarValue, DataFusionError>

Evaluate an expression against a RecordBatch after first applying a validity array

fn evaluate_bounds( &self, _children: &[&Interval], ) -> Result<Interval, DataFusionError>

Computes the output interval for the expression, given the input intervals.

fn propagate_constraints( &self, _interval: &Interval, _children: &[&Interval], ) -> Result<Option<Vec<Interval>>, DataFusionError>

Updates bounds for child expressions, given a known interval for this expression.

fn evaluate_statistics( &self, children: &[&Distribution], ) -> Result<Distribution, DataFusionError>

Computes the output statistics for the expression, given the input statistics.

fn propagate_statistics( &self, parent: &Distribution, children: &[&Distribution], ) -> Result<Option<Vec<Distribution>>, DataFusionError>

Updates children statistics using the given parent statistic for this expression.

fn get_properties( &self, _children: &[ExprProperties], ) -> Result<ExprProperties, DataFusionError>

Calculates the properties of this PhysicalExpr based on its children’s properties (i.e. order and range), recursively aggregating the information from its children. In cases where the PhysicalExpr has no children (e.g., Literal or Column), these properties should be specified externally, as the function defaults to unknown properties.

fn snapshot(&self) -> Result<Option<Arc<dyn PhysicalExpr>>, DataFusionError>

Take a snapshot of this PhysicalExpr, if it is dynamic.

fn snapshot_generation(&self) -> u64

Returns the generation of this PhysicalExpr for snapshotting purposes. The generation is an arbitrary u64 that can be used to track changes in the state of the PhysicalExpr over time without having to do an exhaustive comparison. This is useful to avoid unnecessary computation or serialization if there are no changes to the expression. In particular, dynamic expressions that may change over time; this allows cheap checks for changes. Static expressions that do not change over time should return 0, as does the default implementation. You should not call this method directly as it does not handle recursion. Instead use snapshot_generation to handle recursion and capture the full state of the PhysicalExpr.

fn is_volatile_node(&self) -> bool

Returns true if the expression node is volatile, i.e. whether it can return different results when evaluated multiple times with the same input.

impl Eq for CaseExpr

impl StructuralPartialEq for CaseExpr