Trait Dialect 

pub trait Dialect:
    Debug
    + Send
    + Sync {
    // Required methods
    fn write_arg(&self, w: &mut SqlWriter<'_>, position: usize);
    fn write_quoted(&self, w: &mut SqlWriter<'_>, s: &str);

    // Provided method
    fn write_named_arg(&self, w: &mut SqlWriter<'_>, _name: &str) { ... }
}

The per-database syntax an expression needs in order to render itself.

The three dialects keelson targets differ only in these decisions:

dialect	placeholder	quote	named
PostgreSQL	$1	"id"	unsupported
MySQL	? (position ignored)	`id`	unsupported
SQLite	?1	"id"	:name

bob splits named-argument support into a second DialectWithNamed interface and type-asserts on it. We keep one trait with a defaulted method instead, so resolution stays static and “this dialect cannot do that” is one recorded error rather than a failed downcast.

All three methods are infallible. They append to the writer’s buffer, and writing into a String cannot fail; the one real failure — a named argument asked of a dialect that has none — is recorded on the writer with SqlWriter::record_error and surfaced later by build.

Implementing

Write only through SqlWriter::push_str. Never call SqlWriter::push_arg from inside write_arg: that is the method push_arg calls, and it is the only place the placeholder counter advances.

Required Methods

fn write_arg(&self, w: &mut SqlWriter<'_>, position: usize)

Write the placeholder for the argument at position (1-based).

A dialect with positional placeholders ignores position — the argument order carries the meaning instead.

fn write_quoted(&self, w: &mut SqlWriter<'_>, s: &str)

Write s as a quoted identifier, including the quote characters.

Provided Methods

fn write_named_arg(&self, w: &mut SqlWriter<'_>, _name: &str)

Write the placeholder for a named argument.

Defaults to recording Error::NoNamedArgs; only SQLite overrides it.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementations on Foreign Types

impl<D: Dialect + ?Sized> Dialect for &D

fn write_arg(&self, w: &mut SqlWriter<'_>, position: usize)

fn write_quoted(&self, w: &mut SqlWriter<'_>, s: &str)

fn write_named_arg(&self, w: &mut SqlWriter<'_>, name: &str)

Implementors