Module explain

A set of traits for modeling things that can be explained by a SQL EXPLAIN statement.

The main trait in this module is Explain.

An explainable subject S implements Explain, and as part of that:

1. Fixes the context type required for the explanation. in Explain::Context.
2. Fixes the explanation type for each ExplainFormat in Explain::Text, Explain::Json, ….
3. Provides an explanation type constructor for each supported ExplainFormat from references to S, ExplainConfig , and the current Explain::Context in Explain::explain_text, Explain::explain_json, ….

The same explanation type can be shared by more than one ExplainFormat.

Use UnsupportedFormat and the default explain_$format constructor for Explain to indicate that the implementation does not support this $format.

Re-exports

pub use crate::explain::tracing::trace_plan;

Modules

dot

Structs and traits for EXPLAIN AS DOT.

json

Structs and traits for EXPLAIN AS JSON.

text

Structs and traits for EXPLAIN AS TEXT and EXPLAIN AS VERBOSE TEXT.

tracing

Tracing utilities for explainable plans.

Structs

Analyses

A container for derived analyses.

AnnotatedPlan

A somewhat ad-hoc way to keep carry a plan with a set of analyses derived for each node in that plan.

CompactScalarSeq

Pretty-prints a list of scalar expressions that may have runs of column indices as a comma-separated list interleaved with interval expressions.

CompactScalars

Pretty-prints a list of scalar expressions that may have runs of column indices as a comma-separated list interleaved with interval expressions.

DummyHumanizer

A bare-minimum implementation of ExprHumanizer.

ExplainConfig

A set of options for controlling the output of Explain implementations.

ExprHumanizerExt

An ExprHumanizer that extends the inner instance with shadow items that are reported as present, even though they might not exist in inner.

HumanizedAnalyses

Indices

Pretty-prints a list of indices.

PlanRenderingContext

RenderingContext

A helper struct which will most commonly be used as the generic rendering context type C for various Explain$Format implementations.

TransientItem

A description of a catalog item that does not exist, but can be reported as present in the catalog by a ExprHumanizerExt instance that has it in its items list.

UsedIndexes

A set of indexes that are used in the explained plan.

Enums

DeltaJoinIndexUsageType

In a snapshot, one arrangement of the first input is scanned, all the other arrangements (of the first input, and of all other inputs) only get lookups. When later input batches are arriving, all inputs are fully read.

ExplainError

The type of errors that may occur when an Explain::explain call goes wrong.

ExplainFormat

Possible output formats for an explanation.

Explainee

The type of object to be explained

IndexUsageType

UnsupportedFormat

A zero-variant enum to be used as the explanation type in the Explain implementation for all formats that are not supported for Self.

Traits

Explain

A trait that provides a unified interface for objects that can be explained.

ExprHumanizer

A trait for humanizing components of an expression.

ScalarOps