Enum mz_transform::optimizer_notices::OptimizerNotice

pub enum OptimizerNotice {
    IndexTooWideForLiteralConstraints(IndexTooWideForLiteralConstraints),
    IndexKeyEmpty,
}

Notices that the optimizer wants to show to users.

Variants

IndexTooWideForLiteralConstraints(IndexTooWideForLiteralConstraints)

IndexKeyEmpty

An index with an empty key is maximally skewed (all of the data goes to a single worker), and is almost never really useful. It’s slightly useful for a cross join, because a cross join also has an empty key, so we avoid rearranging the input. However, this is still not very useful, because

• Rearranging the input shouldn’t take too much memory, because if a cross join has a big input, then we have a serious problem anyway.
• Even with the arrangement already there, the cross join will read every input record, so the orders of magnitude performance improvements that can happen with other joins when an input arrangement exists can’t happen with a cross join. Also note that skew is hard to debug, so it’s good to avoid this problem in the first place.

Implementations

impl OptimizerNotice

pub fn to_string(&self, humanizer: &dyn ExprHumanizer) -> (String, String)

Turns the OptimizerNotice into a string, using the given ExprHumanizer.

pub fn explain( notices: &Vec<OptimizerNotice>, humanizer: &dyn ExprHumanizer ) -> Result<Vec<String>, Error>

Turns a Vec<OptimizerNotice> into a String that can be used in EXPLAIN.

pub fn is_valid(&self, humanizer: &dyn ExprHumanizer) -> bool

Returns whether the ids mentioned in the notice still exist.

pub fn metric_label(&self) -> &str

A notice name, which will be applied as the label on the metric that is counting notices labelled by notice type.

Trait Implementations

impl Clone for OptimizerNotice

fn clone(&self) -> OptimizerNotice

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for OptimizerNotice

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

Formats the value using the given formatter.

impl PartialEq for OptimizerNotice

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

This method tests for self and other values to be equal, and is used by ==.

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

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

impl Eq for OptimizerNotice

impl StructuralEq for OptimizerNotice

impl StructuralPartialEq for OptimizerNotice