Merge pull request diesel-rs#3093 from Justice4Joffrey/oc-pg-updating-array

Enable expressions on the left-hand side of update.set()

Author: weiznich

CHANGELOG.md

@@ -84,6 +84,8 @@ Increasing the minimal supported Rust version will always be coupled at least wi
 
 * Added support for the usage of slices of references with `belonging_to` from `BelongingToDsl`
 
+* Added support for updating individual array elements `UPDATE table SET array_column[1] = true`
+
 ### Removed
 
 * All previously deprecated items have been removed.

diesel/src/pg/expression/operators.rs

@@ -1,10 +1,13 @@
+use crate::backend::{Backend, DieselReserveSpecialization};
 use crate::expression::expression_types::NotSelectable;
 use crate::expression::{TypedExpressionType, ValidGrouping};
 use crate::pg::Pg;
-use crate::query_builder::{QueryFragment, QueryId};
+use crate::query_builder::update_statement::changeset::AssignmentTarget;
+use crate::query_builder::{AstPass, QueryFragment, QueryId};
 use crate::sql_types::{
     Array, Bigint, Bool, DieselNumericOps, Inet, Integer, Jsonb, SqlType, Text,
 };
+use crate::{Column, QueryResult};
 
 __diesel_infix_operator!(IsDistinctFrom, " IS DISTINCT FROM ", ConstantNullability Bool, backend: Pg);
 __diesel_infix_operator!(IsNotDistinctFrom, " IS NOT DISTINCT FROM ", ConstantNullability Bool, backend: Pg);
@@ -90,3 +93,31 @@ where
         Ok(())
     }
 }
+
+impl<L, R> AssignmentTarget for ArrayIndex<L, R>
+where
+    L: Column,
+{
+    type Table = <L as Column>::Table;
+    type QueryAstNode = ArrayIndex<UncorrelatedColumn<L>, R>;
+
+    fn into_target(self) -> Self::QueryAstNode {
+        ArrayIndex::new(UncorrelatedColumn(self.array_expr), self.index_expr)
+    }
+}
+
+/// Signifies that this column should be rendered without its 'correlation'
+/// (i.e. table name prefix). For update statements, fully qualified column
+/// names aren't allowed.
+#[derive(Debug)]
+pub struct UncorrelatedColumn<C>(C);
+
+impl<C, DB> QueryFragment<DB> for UncorrelatedColumn<C>
+where
+    C: Column,
+    DB: Backend + DieselReserveSpecialization,
+{
+    fn walk_ast<'b>(&'b self, mut out: AstPass<'_, 'b, DB>) -> QueryResult<()> {
+        out.push_identifier(C::NAME)
+    }
+}

diesel/src/query_builder/mod.rs

@@ -30,7 +30,7 @@ mod returning_clause;
 pub(crate) mod select_clause;
 pub(crate) mod select_statement;
 mod sql_query;
-mod update_statement;
+pub(crate) mod update_statement;
 pub(crate) mod upsert;
 mod where_clause;
 

diesel/src/query_builder/update_statement/changeset.rs

@@ -1,10 +1,11 @@
-use crate::backend::Backend;
+use crate::backend::{Backend, DieselReserveSpecialization};
 use crate::expression::grouped::Grouped;
 use crate::expression::operators::Eq;
 use crate::expression::AppearsOnTable;
 use crate::query_builder::*;
 use crate::query_source::{Column, QuerySource};
 use crate::result::QueryResult;
+use crate::Table;
 
 /// Types which can be passed to
 /// [`update.set`](UpdateStatement::set()).
@@ -40,15 +41,15 @@ impl<T: AsChangeset> AsChangeset for Option<T> {
 
 impl<Left, Right> AsChangeset for Eq<Left, Right>
 where
-    Left: Column,
+    Left: AssignmentTarget,
     Right: AppearsOnTable<Left::Table>,
 {
     type Target = Left::Table;
-    type Changeset = Assign<Left, Right>;
+    type Changeset = Assign<<Left as AssignmentTarget>::QueryAstNode, Right>;
 
     fn as_changeset(self) -> Self::Changeset {
         Assign {
-            _column: self.left,
+            target: self.left.into_target(),
             expr: self.right,
         }
     }
@@ -68,20 +69,63 @@ where
 }
 
 #[derive(Debug, Clone, Copy, QueryId)]
-pub struct Assign<Col, Expr> {
-    _column: Col,
+pub struct Assign<Target, Expr> {
+    target: Target,
     expr: Expr,
 }
 
 impl<T, U, DB> QueryFragment<DB> for Assign<T, U>
 where
     DB: Backend,
-    T: Column,
+    T: QueryFragment<DB>,
     U: QueryFragment<DB>,
 {
     fn walk_ast<'b>(&'b self, mut out: AstPass<'_, 'b, DB>) -> QueryResult<()> {
-        out.push_identifier(T::NAME)?;
+        QueryFragment::walk_ast(&self.target, out.reborrow())?;
         out.push_sql(" = ");
-        QueryFragment::walk_ast(&self.expr, out)
+        QueryFragment::walk_ast(&self.expr, out.reborrow())
+    }
+}
+
+/// Represents the left hand side of an assignment expression for an
+/// assignment in [AsChangeset]. The vast majority of the time, this will
+/// be a [Column]. However, in certain database backends, it's possible to
+/// assign to an expression. For example, in Postgres, it's possible to
+/// "UPDATE TABLE SET array_column\[1\] = 'foo'".
+pub trait AssignmentTarget {
+    /// Table the assignment is to
+    type Table: Table;
+    /// A wrapper around a type to assign to (this wrapper should implement
+    /// [QueryFragment]).
+    type QueryAstNode;
+
+    /// Move this in to the AST node which should implement [QueryFragment].
+    fn into_target(self) -> Self::QueryAstNode;
+}
+
+/// Represents a `Column` as an `AssignmentTarget`. The vast majority of
+/// targets in an update statement will be `Column`s.
+#[derive(Debug, Clone, Copy)]
+pub struct ColumnWrapperForUpdate<C>(pub C);
+
+impl<DB, C> QueryFragment<DB> for ColumnWrapperForUpdate<C>
+where
+    DB: Backend + DieselReserveSpecialization,
+    C: Column,
+{
+    fn walk_ast<'b>(&'b self, mut out: AstPass<'_, 'b, DB>) -> QueryResult<()> {
+        out.push_identifier(C::NAME)
+    }
+}
+
+impl<C> AssignmentTarget for C
+where
+    C: Column,
+{
+    type Table = C::Table;
+    type QueryAstNode = ColumnWrapperForUpdate<C>;
+
+    fn into_target(self) -> Self::QueryAstNode {
+        ColumnWrapperForUpdate(self)
     }
 }

diesel/src/query_builder/update_statement/mod.rs

@@ -1,4 +1,4 @@
-pub(super) mod changeset;
+pub(crate) mod changeset;
 pub(super) mod target;
 
 use self::target::UpdateTarget;

diesel_compile_tests/Cargo.lock

@@ -189,7 +189,7 @@ error[E0277]: the trait bound `{integer}: QueryFragment<Pg>` is not satisfied
              <() as QueryFragment<DB>>
              <(T0, T1) as QueryFragment<__DB>>
              <(T0, T1, T2) as QueryFragment<__DB>>
-           and 267 others
+           and 269 others
    = note: required because of the requirements on the impl of `QueryFragment<Pg>` for `({integer}, diesel::internal::derives::as_expression::Bound<diesel::sql_types::Double, f64>)`
    = note: 3 redundant requirements hidden
    = note: required because of the requirements on the impl of `QueryFragment<Pg>` for `SelectStatement<NoFromClause, diesel::query_builder::select_clause::SelectClause<diesel::pg::expression::array::ArrayLiteral<({integer}, diesel::internal::derives::as_expression::Bound<diesel::sql_types::Double, f64>), diesel::sql_types::Double>>>`

diesel_compile_tests/tests/fail/array_expressions_must_be_same_type.stderr

@@ -7,7 +7,7 @@ error[E0277]: the trait bound `diesel::expression::is_aggregate::Yes: MixedAggre
    = help: the following implementations were found:
              <diesel::expression::is_aggregate::Yes as MixedAggregates<diesel::expression::is_aggregate::Never>>
              <diesel::expression::is_aggregate::Yes as MixedAggregates<diesel::expression::is_aggregate::Yes>>
-   = note: required because of the requirements on the impl of `Query` for `UpdateStatement<users::table, diesel::query_builder::where_clause::WhereClause<diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<columns::id, diesel::internal::derives::as_expression::Bound<diesel::sql_types::Integer, i32>>>>, diesel::query_builder::update_statement::changeset::Assign<columns::name, diesel::internal::derives::as_expression::Bound<diesel::sql_types::Text, &str>>, diesel::query_builder::returning_clause::ReturningClause<diesel::expression::count::count::count<diesel::sql_types::Integer, columns::id>>>`
+   = note: required because of the requirements on the impl of `Query` for `UpdateStatement<users::table, diesel::query_builder::where_clause::WhereClause<diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<columns::id, diesel::internal::derives::as_expression::Bound<diesel::sql_types::Integer, i32>>>>, diesel::query_builder::update_statement::changeset::Assign<diesel::query_builder::update_statement::changeset::ColumnWrapperForUpdate<columns::name>, diesel::internal::derives::as_expression::Bound<diesel::sql_types::Text, &str>>, diesel::query_builder::returning_clause::ReturningClause<diesel::expression::count::count::count<diesel::sql_types::Integer, columns::id>>>`
 
 error[E0277]: the trait bound `diesel::expression::is_aggregate::No: MixedAggregates<diesel::expression::is_aggregate::Yes>` is not satisfied
   --> tests/fail/custom_returning_requires_nonaggregate.rs:27:53

diesel_compile_tests/tests/fail/custom_returning_requires_nonaggregate.stderr

@@ -10,7 +10,7 @@ error[E0277]: the trait bound `bad::columns::age: SelectableExpression<users::ta
              <bad::columns::age as SelectableExpression<SelectStatement<FromClause<From>>>>
              <bad::columns::age as SelectableExpression<bad::table>>
            and 2 others
-   = note: required because of the requirements on the impl of `Query` for `UpdateStatement<users::table, diesel::query_builder::where_clause::WhereClause<diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<users::columns::id, diesel::internal::derives::as_expression::Bound<diesel::sql_types::Integer, i32>>>>, diesel::query_builder::update_statement::changeset::Assign<users::columns::name, diesel::internal::derives::as_expression::Bound<diesel::sql_types::Text, &str>>, diesel::query_builder::returning_clause::ReturningClause<bad::columns::age>>`
+   = note: required because of the requirements on the impl of `Query` for `UpdateStatement<users::table, diesel::query_builder::where_clause::WhereClause<diesel::expression::grouped::Grouped<diesel::expression::operators::Eq<users::columns::id, diesel::internal::derives::as_expression::Bound<diesel::sql_types::Integer, i32>>>>, diesel::query_builder::update_statement::changeset::Assign<diesel::query_builder::update_statement::changeset::ColumnWrapperForUpdate<users::columns::name>, diesel::internal::derives::as_expression::Bound<diesel::sql_types::Text, &str>>, diesel::query_builder::returning_clause::ReturningClause<bad::columns::age>>`
 
 error[E0277]: the trait bound `bad::columns::age: SelectableExpression<users::table>` is not satisfied
   --> tests/fail/custom_returning_requires_selectable_expression.rs:33:63

diesel_compile_tests/tests/fail/custom_returning_requires_selectable_expression.stderr

@@ -10,7 +10,7 @@ error[E0599]: no method named `returning` found for struct `InsertStatement<user
 27 |     query.returning(name);
    |           ^^^^^^^^^ private field, not a method
 
-error[E0599]: no method named `returning` found for struct `UpdateStatement<users::table, diesel::query_builder::where_clause::NoWhereClause, diesel::query_builder::update_statement::changeset::Assign<columns::name, diesel::internal::derives::as_expression::Bound<diesel::sql_types::Text, &str>>, diesel::query_builder::returning_clause::ReturningClause<columns::id>>` in the current scope
+error[E0599]: no method named `returning` found for struct `UpdateStatement<users::table, diesel::query_builder::where_clause::NoWhereClause, diesel::query_builder::update_statement::changeset::Assign<diesel::query_builder::update_statement::changeset::ColumnWrapperForUpdate<columns::name>, diesel::internal::derives::as_expression::Bound<diesel::sql_types::Text, &str>>, diesel::query_builder::returning_clause::ReturningClause<columns::id>>` in the current scope
   --> tests/fail/returning_cannot_be_called_twice.rs:30:11
    |
 30 |     query.returning(name);