Module ast 

rudb’s abstract syntax tree.

The parse tree the matcher produces is DuckDB’s grammar, faithfully. That is the point of it and it is also why nothing downstream should read it: a bump of the vendored grammar is allowed to rename BetweenInLikeExpression, and if the binder is matching on that name then the bump is a rewrite. This module is the boundary. It is ours, it changes when we decide it changes, and transform is the one place that knows both shapes.

Everything is an arena with u32 indices, per spec/04-architecture.md section 4.5. There is no Box and no Vec inside a node. A list of children is a Slice into a side vector, which means a node is a fixed size, the whole tree is a handful of allocations, and walking it is a sequential read rather than a pointer chase per node. It also means an Ast is Clone and Send without any thought, and that a subtree can be addressed by a u32 in a plan or an error without borrowing anything.

The one cost is that you cannot hold a reference to a node and index the arena at the same time, so the code reads a node out by value first. Nodes are small and Copy, so that is a register move.

Structs

Ast

A parsed statement or script, with every arena it points into.

CaseArm

One WHEN a THEN b.

OrderItem

One entry of an order by list.

Query

A query: a body, plus the modifiers that apply to whatever the body produced.

Select

One select block.

Slice

A run of items in one of the side vectors.

Target

One entry of a target list.

Enums

BinaryOp

An infix operator.

Distinct

What the DISTINCT clause of a select said.

Expr

One expression.

JoinKind

Which join.

LiteralKind

Which literal.

Nulls

Null placement in a sort.

Order

Sort direction, with the unwritten case kept apart from the default it resolves to.

Quantifier

Whether a set operator or an aggregate keeps duplicates.

QueryBody

What produces the rows of a query.

SetOp

Which set operator.

Source

One entry in a FROM clause, which is a tree because joins nest.

Statement

One statement.

UnaryOp

A prefix or postfix operator.

Type Aliases

ExprRef

An index into Ast::exprs.

QueryRef

An index into Ast::queries.

SelectRef

An index into Ast::selects.

SourceRef

An index into Ast::sources.

StrRef

An index into Ast::strings.