Class: LazyFrame¶

A lazy evaluation wrapper specialized in Expression-based filtering.

Queues multiple filter operations using Expression instances and applies internal optimizations (predicate fusion, short-circuit evaluation) before materialization.

Remarks¶

LazyFrame accepts only Expression instances for filtering, enabling: - Predicate fusion: multiple filters are combined via AND logic - Short-circuit evaluation: evaluation stops as soon as a condition fails - Future optimizations: predicate reordering by selectivity, pushdown

Use LazyFrame.from(df) to create an instance. Do not construct directly.

Example¶

TypeScript

const df = BareFrame.fromColumns({
  name: ["Alice", "Bob", "Charlie"],
  age: [25, 17, 30],
});

const result = LazyFrame.from(df)
  .filter(Expression.col("age").ge(18))
  .filter(Expression.col("name").startsWith("C"))
  .collect();
// name    | age
// Charlie | 30

Since¶

0.68.0

DataFrame¶

from()¶

static from(source): LazyFrame

Create a new LazyFrame from a BareFrame.

Parameters¶

source¶

BareFrame

Source BareFrame to wrap

Returns¶

LazyFrame

New LazyFrame with empty expression queue

Example¶

TypeScript

const lazy = LazyFrame.from(df)
  .filter(Expression.col("age").ge(18));

Since¶

0.68.0

filter()¶

filter(expr): LazyFrame

Queue a filter operation with an Expression.

Parameters¶

expr¶

Expression

Expression instance defining the filter condition

Returns¶

LazyFrame

New LazyFrame with the filter expression appended

Remarks¶

The expression is stored but not evaluated until collect() is invoked. Multiple filter calls are combined via AND logic during materialization. Important: Do not modify the expression after passing it to filter().

Example¶

TypeScript

const adults = LazyFrame.from(df)
  .filter(Expression.col("age").ge(18))
  .collect();

Since¶

0.68.0

collect()¶

collect(): BareFrame

Execute all queued filter operations and return the materialized result.

Returns¶

BareFrame

Materialized BareFrame with all filter expressions applied

Remarks¶

All queued expressions are fused into a single combined predicate using AND logic. This enables short-circuit evaluation: if any condition fails, the row is rejected immediately without evaluating remaining conditions.

Example¶

TypeScript

const filtered = LazyFrame.from(df)
  .filter(Expression.col("status").eq("active"))
  .filter(Expression.col("age").gt(21))
  .collect();

Since¶

0.68.0