Enum QueryPlan 

pub enum QueryPlan {
    Sqlite(SQLiteQueryBuilder),
}

A lazy query plan that can be composed and executed by filter commands.

This is the deepened seam between filter commands (which want to push down operations like limit, select, count) and database backends (which implement the actual query execution). Each variant wraps a concrete query builder.

Callers interact with this enum through its methods instead of downcasting to a concrete type. Adding a new backend means adding a variant here; filter commands do not change.

Variants

Sqlite(SQLiteQueryBuilder)

SQLite-based lazy query (via SQLiteQueryBuilder).

Implementations

impl QueryPlan

pub fn try_from_any(val: &dyn Any) -> Option<Self>

Try to extract a QueryPlan from a &dyn Any reference.

This is the single place where downcast_ref happens. All filter commands call this instead of importing and downcasting to a concrete query builder type.

pub fn with_limit(self, limit: i64) -> Self

Apply a LIMIT to the query plan.

pub fn with_offset(self, offset: i64) -> Self

Apply an OFFSET to the query plan.

pub fn with_distinct(self) -> Self

Apply a DISTINCT to the query plan.

pub fn with_order_by(self, order_by: String) -> Self

Apply an ORDER BY to the query plan.

pub fn project_output_columns(&self, columns: &[String]) -> Option<Self>

Project the output to a subset of columns.

Returns None if the projection cannot be expressed (e.g. complex column expressions), allowing callers to fall back to in-memory processing.

pub fn execute(&self, call_span: Span) -> Result<PipelineData, ShellError>

Execute the query and return the result as PipelineData.

pub fn count(&self, call_span: Span) -> Result<i64, ShellError>

Count the number of rows without fetching them.

pub fn type_name(&self) -> &'static str

Human-readable type name for error messages.

pub fn into_value(self, span: Span) -> Value

Convert back into a Value::Custom for pipeline propagation.