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//! Contains traits responsible for the actual construction of SQL statements
//!
//! The types in this module are part of Diesel's public API, but are generally
//! only useful for implementing Diesel plugins. Applications should generally
//! not need to care about the types inside of this module.
#[macro_use]
mod query_id;
#[macro_use]
mod clause_macro;
mod ast_pass;
pub mod bind_collector;
pub(crate) mod combination_clause;
mod debug_query;
mod delete_statement;
mod distinct_clause;
pub(crate) mod from_clause;
pub(crate) mod functions;
mod group_by_clause;
mod having_clause;
pub(crate) mod insert_statement;
pub(crate) mod limit_clause;
pub(crate) mod limit_offset_clause;
pub(crate) mod locking_clause;
pub(crate) mod nodes;
pub(crate) mod offset_clause;
pub(crate) mod order_clause;
pub(crate) mod returning_clause;
pub(crate) mod select_clause;
pub(crate) mod select_statement;
mod sql_query;
pub(crate) mod update_statement;
pub(crate) mod upsert;
mod where_clause;
#[doc(inline)]
pub use self::ast_pass::AstPass;
#[doc(inline)]
pub use self::bind_collector::BindCollector;
#[doc(inline)]
pub use self::debug_query::DebugQuery;
#[doc(inline)]
pub use self::delete_statement::{BoxedDeleteStatement, DeleteStatement};
#[doc(inline)]
pub use self::insert_statement::{
IncompleteInsertOrIgnoreStatement, IncompleteInsertStatement, IncompleteReplaceStatement,
InsertOrIgnoreStatement, InsertStatement, ReplaceStatement,
};
#[doc(inline)]
pub use self::query_id::QueryId;
#[doc(inline)]
pub use self::sql_query::{BoxedSqlQuery, SqlQuery};
#[doc(inline)]
pub use self::upsert::on_conflict_target_decorations::DecoratableTarget;
#[doc(inline)]
pub use self::update_statement::changeset::AsChangeset;
#[doc(inline)]
pub use self::update_statement::target::{IntoUpdateTarget, UpdateTarget};
#[doc(inline)]
pub use self::update_statement::{BoxedUpdateStatement, UpdateStatement};
#[cfg(feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes")]
pub use self::limit_clause::{LimitClause, NoLimitClause};
#[cfg(feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes")]
pub use self::limit_offset_clause::{BoxedLimitOffsetClause, LimitOffsetClause};
#[cfg(feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes")]
pub use self::offset_clause::{NoOffsetClause, OffsetClause};
#[diesel_derives::__diesel_public_if(
feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
)]
#[doc(inline)]
pub(crate) use self::insert_statement::batch_insert::BatchInsert;
#[diesel_derives::__diesel_public_if(
feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
)]
pub(crate) use self::insert_statement::{UndecoratedInsertRecord, ValuesClause};
#[cfg(feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes")]
#[doc(inline)]
pub use self::insert_statement::DefaultValues;
#[cfg(feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes")]
#[doc(inline)]
pub use self::returning_clause::ReturningClause;
#[doc(inline)]
#[diesel_derives::__diesel_public_if(
feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
)]
pub(crate) use self::ast_pass::AstPassToSqlOptions;
#[doc(inline)]
#[diesel_derives::__diesel_public_if(
feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
)]
pub(crate) use self::select_clause::SelectClauseExpression;
#[doc(inline)]
#[diesel_derives::__diesel_public_if(
feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
)]
pub(crate) use self::from_clause::{FromClause, NoFromClause};
#[diesel_derives::__diesel_public_if(
feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
)]
#[doc(inline)]
pub(crate) use self::select_statement::BoxedSelectStatement;
#[diesel_derives::__diesel_public_if(
feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
)]
#[doc(inline)]
pub(crate) use self::select_statement::SelectStatement;
pub(crate) use self::insert_statement::ColumnList;
#[cfg(feature = "postgres_backend")]
pub use crate::pg::query_builder::only::Only;
use crate::backend::{Backend, HasBindCollector};
use crate::result::QueryResult;
use std::error::Error;
#[doc(hidden)]
pub type Binds = Vec<Option<Vec<u8>>>;
/// A specialized Result type used with the query builder.
pub type BuildQueryResult = Result<(), Box<dyn Error + Send + Sync>>;
/// Constructs a SQL query from a Diesel AST.
///
/// The only reason you should ever need to interact with this trait is if you
/// are extending Diesel with support for a new backend. Plugins which extend
/// the query builder with new capabilities will interact with [`AstPass`]
/// instead.
///
pub trait QueryBuilder<DB: Backend> {
/// Add `sql` to the end of the query being constructed.
fn push_sql(&mut self, sql: &str);
/// Quote `identifier`, and add it to the end of the query being
/// constructed.
fn push_identifier(&mut self, identifier: &str) -> QueryResult<()>;
/// Add a placeholder for a bind parameter to the end of the query being
/// constructed.
fn push_bind_param(&mut self);
/// Increases the internal counter for bind parameters without adding the
/// bind parameter itself to the query
fn push_bind_param_value_only(&mut self) {}
/// Returns the constructed SQL query.
fn finish(self) -> String;
}
/// A complete SQL query with a return type.
///
/// This can be a select statement, or a command such as `update` or `insert`
/// with a `RETURNING` clause. Unlike [`Expression`], types implementing this
/// trait are guaranteed to be executable on their own.
///
/// A type which doesn't implement this trait may still represent a complete SQL
/// query. For example, an `INSERT` statement without a `RETURNING` clause will
/// not implement this trait, but can still be executed.
///
/// [`Expression`]: crate::expression::Expression
pub trait Query {
/// The SQL type that this query represents.
///
/// This is the SQL type of the `SELECT` clause for select statements, and
/// the SQL type of the `RETURNING` clause for insert, update, or delete
/// statements.
type SqlType;
}
impl<'a, T: Query> Query for &'a T {
type SqlType = T::SqlType;
}
/// Indicates that a type is a `SELECT` statement.
///
/// This trait differs from `Query` in two ways:
/// - It is implemented only for select statements, rather than all queries
/// which return a value.
/// - It has looser constraints. A type implementing `SelectQuery` is known to
/// be potentially valid if used as a subselect, but it is not necessarily
/// able to be executed.
pub trait SelectQuery {
/// The SQL type of the `SELECT` clause
type SqlType;
}
/// An untyped fragment of SQL.
///
/// This may be a complete SQL command (such as an update statement without a
/// `RETURNING` clause), or a subsection (such as our internal types used to
/// represent a `WHERE` clause). Implementations of [`ExecuteDsl`] and
/// [`LoadQuery`] will generally require that this trait be implemented.
///
/// [`ExecuteDsl`]: crate::query_dsl::methods::ExecuteDsl
/// [`LoadQuery`]: crate::query_dsl::methods::LoadQuery
pub trait QueryFragment<DB: Backend, SP = self::private::NotSpecialized> {
/// Walk over this `QueryFragment` for all passes.
///
/// This method is where the actual behavior of an AST node is implemented.
/// This method will contain the behavior required for all possible AST
/// passes. See [`AstPass`] for more details.
///
fn walk_ast<'b>(&'b self, pass: AstPass<'_, 'b, DB>) -> QueryResult<()>;
/// Converts this `QueryFragment` to its SQL representation.
///
/// This method should only be called by implementations of `Connection`.
#[diesel_derives::__diesel_public_if(
feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
)]
fn to_sql(&self, out: &mut DB::QueryBuilder, backend: &DB) -> QueryResult<()> {
let mut options = AstPassToSqlOptions::default();
self.walk_ast(AstPass::to_sql(out, &mut options, backend))
}
/// Serializes all bind parameters in this query.
///
/// A bind parameter is a value which is sent separately from the query
/// itself. It is represented in SQL with a placeholder such as `?` or `$1`.
///
/// This method should only be called by implementations of `Connection`.
#[diesel_derives::__diesel_public_if(
feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
)]
fn collect_binds<'b>(
&'b self,
out: &mut <DB as HasBindCollector<'b>>::BindCollector,
metadata_lookup: &mut DB::MetadataLookup,
backend: &'b DB,
) -> QueryResult<()> {
self.walk_ast(AstPass::collect_binds(out, metadata_lookup, backend))
}
/// Is this query safe to store in the prepared statement cache?
///
/// In order to keep our prepared statement cache at a reasonable size, we
/// avoid caching any queries which represent a potentially unbounded number
/// of SQL queries. Generally this will only return `true` for queries for
/// which `to_sql` will always construct exactly identical SQL.
///
/// Some examples of where this method will return `false` are:
///
/// - `SqlLiteral` (We don't know if the SQL was constructed dynamically, so
/// we must assume that it was)
/// - `In` and `NotIn` (Each value requires a separate bind param
/// placeholder)
///
/// This method should only be called by implementations of `Connection`.
#[diesel_derives::__diesel_public_if(
feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
)]
fn is_safe_to_cache_prepared(&self, backend: &DB) -> QueryResult<bool> {
let mut result = true;
self.walk_ast(AstPass::is_safe_to_cache_prepared(&mut result, backend))?;
Ok(result)
}
/// Does walking this AST have any effect?
#[diesel_derives::__diesel_public_if(
feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
)]
fn is_noop(&self, backend: &DB) -> QueryResult<bool> {
let mut result = true;
self.walk_ast(AstPass::is_noop(&mut result, backend))?;
Ok(result)
}
}
impl<T: ?Sized, DB> QueryFragment<DB> for Box<T>
where
DB: Backend,
T: QueryFragment<DB>,
{
fn walk_ast<'b>(&'b self, pass: AstPass<'_, 'b, DB>) -> QueryResult<()> {
QueryFragment::walk_ast(&**self, pass)
}
}
impl<'a, T: ?Sized, DB> QueryFragment<DB> for &'a T
where
DB: Backend,
T: QueryFragment<DB>,
{
fn walk_ast<'b>(&'b self, pass: AstPass<'_, 'b, DB>) -> QueryResult<()> {
QueryFragment::walk_ast(&**self, pass)
}
}
impl<DB: Backend> QueryFragment<DB> for () {
fn walk_ast<'b>(&'b self, _: AstPass<'_, 'b, DB>) -> QueryResult<()> {
Ok(())
}
}
impl<T, DB> QueryFragment<DB> for Option<T>
where
DB: Backend,
T: QueryFragment<DB>,
{
fn walk_ast<'b>(&'b self, out: AstPass<'_, 'b, DB>) -> QueryResult<()> {
match *self {
Some(ref c) => c.walk_ast(out),
None => Ok(()),
}
}
}
/// A trait used to construct type erased boxed variant of the current query node
///
/// Mainly useful for implementing third party backends
pub trait IntoBoxedClause<'a, DB> {
/// Resulting type
type BoxedClause;
/// Convert the given query node in it's boxed representation
fn into_boxed(self) -> Self::BoxedClause;
}
/// Types that can be converted into a complete, typed SQL query.
///
/// This is used internally to automatically add the right select clause when
/// none is specified, or to automatically add `RETURNING *` in certain contexts.
///
/// A type which implements this trait is guaranteed to be valid for execution.
pub trait AsQuery {
/// The SQL type of `Self::Query`
type SqlType;
/// What kind of query does this type represent?
type Query: Query<SqlType = Self::SqlType>;
/// Converts a type which semantically represents a SQL query into the
/// actual query being executed. See the trait level docs for more.
// This method is part of our public API,
// so we won't change the name to just appease clippy
// (Also the trait is literally named `AsQuery` so
// naming the method similary is fine)
#[allow(clippy::wrong_self_convention)]
fn as_query(self) -> Self::Query;
}
impl<T: Query> AsQuery for T {
type SqlType = <T as Query>::SqlType;
type Query = T;
fn as_query(self) -> <T as AsQuery>::Query {
self
}
}
/// Takes a query `QueryFragment` expression as an argument and returns a type
/// that implements `fmt::Display` and `fmt::Debug` to show the query.
///
/// The `Display` implementation will show the exact query being sent to the
/// server, with a comment showing the values of the bind parameters. The
/// `Debug` implementation will include the same information in a more
/// structured form, and respects pretty printing.
///
/// # Example
///
/// ### Returning SQL from a count statement:
///
/// ```rust
/// # include!("../doctest_setup.rs");
/// #
/// # use diesel::*;
/// # use schema::*;
/// #
/// # fn main() {
/// # use schema::users::dsl::*;
/// let sql = debug_query::<DB, _>(&users.count()).to_string();
/// # if cfg!(feature = "postgres") {
/// # assert_eq!(sql, r#"SELECT COUNT(*) FROM "users" -- binds: []"#);
/// # } else {
/// assert_eq!(sql, "SELECT COUNT(*) FROM `users` -- binds: []");
/// # }
///
/// let query = users.find(1);
/// let debug = debug_query::<DB, _>(&query);
/// # if cfg!(feature = "postgres") {
/// # assert_eq!(debug.to_string(), "SELECT \"users\".\"id\", \"users\".\"name\" \
/// # FROM \"users\" WHERE (\"users\".\"id\" = $1) -- binds: [1]");
/// # } else {
/// assert_eq!(debug.to_string(), "SELECT `users`.`id`, `users`.`name` FROM `users` \
/// WHERE (`users`.`id` = ?) -- binds: [1]");
/// # }
///
/// let debug = format!("{:?}", debug);
/// # if !cfg!(feature = "postgres") { // Escaping that string is a pain
/// let expected = "Query { \
/// sql: \"SELECT `users`.`id`, `users`.`name` FROM `users` WHERE \
/// (`users`.`id` = ?)\", \
/// binds: [1] \
/// }";
/// assert_eq!(debug, expected);
/// # }
/// # }
/// ```
pub fn debug_query<DB, T>(query: &T) -> DebugQuery<'_, T, DB> {
DebugQuery::new(query)
}
mod private {
#[allow(missing_debug_implementations, missing_copy_implementations)]
pub struct NotSpecialized;
}