Crate sqltk

Source
Expand description

This crate implements an enhanced Visitor implementation suitable for semantic analysis of SQL.

The AST is provided by the sqlparser crate - which this crate re-exports.

§Key features

  1. Full coverage of all AST node types from sqlparser (including all field types and container types (Vec, Option & Box)) and terminal nodes.

  2. Support for annotating AST nodes with user-defined metadata during traversal (see: [sqltk-analysis])

  3. An API for composing Visitor implementations to facilitate complex SQL analysis scenarios made from small, unit testable pieces (see: [sqltk-analysis]).

§Installation

$ cargo install cargo-expand
$ cargo add sqltk
# optional:
$ cargo add sqltk-analysis

§Example

Count the number of Expr nodes in an AST.

use std::cell::Cell;
use std::convert::Infallible;
use std::ops::ControlFlow;
use sqltk::{Visitor, Visitable, into_result, Break};
use sqlparser::{ast::Expr, dialect::GenericDialect, parser::Parser};

let dialect = GenericDialect {};

let sql = "SELECT a, b, 123, myfunc(b) \
           FROM table_1 \
           WHERE a > b AND b < 100 \
           ORDER BY a DESC, b";

let ast = Parser::parse_sql(&dialect, sql).unwrap();

struct CountOfExprNodes{ count: Cell<usize> };

impl<'ast> Visitor<'ast> for CountOfExprNodes {
    type Error = Infallible;

    fn enter<N: Visitable>(&mut self, node: &'ast N) -> ControlFlow<Break<Self::Error>> {
        if let Some(expr) = node.downcast_ref::<Expr>() {
           self.count.set(self.count.get() + 1);
        }
        ControlFlow::Continue(())
    }
}

// The expressions are:
//   In the SELECT projection: a, b, 123, myfunc(b), b
//   In the WHERE clause: a, b, a > b, b, 100, b < 100, a > b AND b < 100
//   In the ORDER BY clause: a, b
// Total: 14

let mut visitor = CountOfExprNodes{ count: Cell::new(0) };

match into_result(ast.accept(&mut visitor)) {
    Ok(()) => assert_eq!(14, visitor.count.get()),
    err => panic!("{:#?}", err)
};

Enums§

  • Break
    Type used to signal abnormal control flow from a Visitor during AST traversal.

Traits§

  • Semantic
    Marker trait for AST nodes that are semantically interesting. Every type that implements Visitable is semantically interesting except for Box<T: Visitable> and Option<T: Visitable>
  • Transform
    Trait for producing a new AST node from an existing one by applying edits.
  • Transformable
    Trait for applying a Transform to an AST to produce an edited version.
  • Visitable
    Trait for types that can be traversed by a Visitor.
  • Visitor
    Trait for types that can visit any sqlparser AST node.

Functions§