Module mz_repr::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.
• tracing
  Tracing utilities for explainable plans.

Structs

• AnnotatedPlan
  A somewhat ad-hoc way to keep carry a plan with a set of attributes derived for each node in that plan.
• Attributes
  A container for derived attributes.
• 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.
• HumanizedAttributes
• 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

• 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