neosqlite.collection.expr_evaluator.context module

Context management and helper functions for expression evaluation.

This module provides the AggregationContext class for managing variable scoping and helper functions for identifying different types of expression values.

Note: Type checking helpers (_is_expression, _is_field_reference, _is_literal) have been moved to collection.type_utils for shared use across subpackages. They are re-exported here for backward compatibility.

class neosqlite.collection.expr_evaluator.context.AggregationContext

Bases: object

Manages variable scoping for aggregation expressions.

Aggregation expressions have different variable contexts than query expressions. This class manages the lifecycle of aggregation variables like $$ROOT, $$CURRENT, and $$REMOVE throughout pipeline execution.

variables

Dictionary mapping variable names to their values

stage_index

Current stage index in the pipeline

current_field

Name of the field being computed (for context)

pipeline_id

Unique identifier for the pipeline (for temp table correlation)

__init__() → None

Initialize aggregation context with default variables.

bind_document(doc: dict[str, Any]) → None

Bind document to context.

Called at the start of pipeline execution to initialize $$ROOT and $$CURRENT with the input document.

Parameters:

doc – The document to bind

update_current(doc: dict[str, Any]) → None

Update current document after stage processing.

Called after each stage that modifies the document to update the $$CURRENT variable.

Parameters:

doc – The updated document

get_variable(name: str) → Any

Get variable value.

Parameters:

name – Variable name (e.g., “$$ROOT”, “$$CURRENT”)

Returns:

Variable value or None if not found

set_variable(name: str, value: Any) → None

Set variable value.

Parameters:

• name – Variable name

• value – Value to set

clone() → AggregationContext

Create a shallow copy of the context for nested scoping.

Returns:

A copy of the context.

Return type:

AggregationContext

neosqlite.collection.expr_evaluator.context._is_aggregation_variable(value: Any) → bool

Check for aggregation variables.

Aggregation variables start with ‘$$’ (e.g., $$ROOT, $$CURRENT).

Parameters:

value – Value to check

Returns:

True if value is an aggregation variable, False otherwise

Examples

>>> _is_aggregation_variable("$$ROOT")
True
>>> _is_aggregation_variable("$$CURRENT")
True
>>> _is_aggregation_variable("$field")
False