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use expression::{AppearsOnTable, Expression};
use pg::Pg;
use query_builder::*;
use query_source::*;
use result::QueryResult;
pub fn excluded<T>(excluded: T) -> Excluded<T> {
Excluded(excluded)
}
#[doc(hidden)]
#[derive(Debug, Clone, Copy)]
pub struct DoNothing;
impl QueryFragment<Pg> for DoNothing {
fn walk_ast(&self, mut out: AstPass<Pg>) -> QueryResult<()> {
out.push_sql(" DO NOTHING");
Ok(())
}
}
#[doc(hidden)]
#[derive(Debug, Clone, Copy)]
pub struct DoUpdate<T> {
changeset: T,
}
impl<T> DoUpdate<T> {
pub(crate) fn new(changeset: T) -> Self {
DoUpdate { changeset }
}
}
impl<T> QueryFragment<Pg> for DoUpdate<T>
where
T: QueryFragment<Pg>,
{
fn walk_ast(&self, mut out: AstPass<Pg>) -> QueryResult<()> {
out.unsafe_to_cache_prepared();
if self.changeset.is_noop()? {
out.push_sql(" DO NOTHING");
} else {
out.push_sql(" DO UPDATE SET ");
self.changeset.walk_ast(out.reborrow())?;
}
Ok(())
}
}
#[doc(hidden)]
#[derive(Debug, Clone, Copy)]
pub struct Excluded<T>(T);
impl<T> QueryFragment<Pg> for Excluded<T>
where
T: Column,
{
fn walk_ast(&self, mut out: AstPass<Pg>) -> QueryResult<()> {
out.push_sql("excluded.");
out.push_identifier(T::NAME)?;
Ok(())
}
}
impl<T> Expression for Excluded<T>
where
T: Expression,
{
type SqlType = T::SqlType;
}
impl<T> AppearsOnTable<T::Table> for Excluded<T>
where
T: Column,
Excluded<T>: Expression,
{
}