Add Postgres Json functions: JSON_BUILD_OBJECT and JSON_AGG (#787)

* feat: add `json_build_object` function for postgres

* feat: add `json_agg` function for postgres

* style: add newlines

* chore: apply linting suggestions

* fix: tests for not_equals

src/backend/postgres/query.rs

@@ -122,6 +122,8 @@ impl QueryBuilder for PostgresQueryBuilder {
                     PgFunction::TsRankCd => "TS_RANK_CD",
                     PgFunction::StartsWith => "STARTS_WITH",
                     PgFunction::GenRandomUUID => "GEN_RANDOM_UUID",
+                    PgFunction::JsonBuildObject => "JSON_BUILD_OBJECT",
+                    PgFunction::JsonAgg => "JSON_AGG",
                     #[cfg(feature = "postgres-array")]
                     PgFunction::Any => "ANY",
                     #[cfg(feature = "postgres-array")]

src/expr.rs

@@ -614,20 +614,20 @@ impl Expr {
     /// let query = Query::select()
     ///     .columns([Char::Character, Char::SizeW, Char::SizeH])
     ///     .from(Char::Table)
-    ///     .and_where(Expr::col((Char::Table, Char::FontId)).equals((Font::Table, Font::Id)))
+    ///     .and_where(Expr::col((Char::Table, Char::FontId)).not_equals((Font::Table, Font::Id)))
     ///     .to_owned();
     ///
     /// assert_eq!(
     ///     query.to_string(MysqlQueryBuilder),
-    ///     r#"SELECT `character`, `size_w`, `size_h` FROM `character` WHERE `character`.`font_id` = `font`.`id`"#
+    ///     r#"SELECT `character`, `size_w`, `size_h` FROM `character` WHERE `character`.`font_id` <> `font`.`id`"#
     /// );
     /// assert_eq!(
     ///     query.to_string(PostgresQueryBuilder),
-    ///     r#"SELECT "character", "size_w", "size_h" FROM "character" WHERE "character"."font_id" = "font"."id""#
+    ///     r#"SELECT "character", "size_w", "size_h" FROM "character" WHERE "character"."font_id" <> "font"."id""#
     /// );
     /// assert_eq!(
     ///     query.to_string(SqliteQueryBuilder),
-    ///     r#"SELECT "character", "size_w", "size_h" FROM "character" WHERE "character"."font_id" = "font"."id""#
+    ///     r#"SELECT "character", "size_w", "size_h" FROM "character" WHERE "character"."font_id" <> "font"."id""#
     /// );
     /// ```
     pub fn not_equals<C>(self, col: C) -> SimpleExpr

src/extension/postgres/func.rs

@@ -14,6 +14,8 @@ pub enum PgFunction {
     TsRankCd,
     StartsWith,
     GenRandomUUID,
+    JsonBuildObject,
+    JsonAgg,
     #[cfg(feature = "postgres-array")]
     Any,
     #[cfg(feature = "postgres-array")]
@@ -350,4 +352,59 @@ impl PgFunc {
     pub fn gen_random_uuid() -> FunctionCall {
         FunctionCall::new(Function::PgFunction(PgFunction::GenRandomUUID))
     }
+
+    /// Call the `JSON_BUILD_OBJECT` function. Postgres only.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use sea_query::{tests_cfg::*, *};
+    ///
+    /// let query = Query::select()
+    ///     .expr(PgFunc::json_build_object(vec![
+    ///         (Expr::val("a"), Expr::val(1)),
+    ///         (Expr::val("b"), Expr::val("2")),
+    ///     ]))
+    ///     .to_owned();
+    ///
+    /// assert_eq!(
+    ///     query.to_string(PostgresQueryBuilder),
+    ///     r#"SELECT JSON_BUILD_OBJECT('a', 1, 'b', '2')"#
+    /// );
+    /// ```
+    pub fn json_build_object<T>(pairs: Vec<(T, T)>) -> FunctionCall
+    where
+        T: Into<SimpleExpr>,
+    {
+        let mut args = vec![];
+        for (key, value) in pairs {
+            args.push(key.into());
+            args.push(value.into());
+        }
+        FunctionCall::new(Function::PgFunction(PgFunction::JsonBuildObject)).args(args)
+    }
+
+    /// Call the `JSON_AGG` function. Postgres only.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use sea_query::{tests_cfg::*, *};
+    ///
+    /// let query = Query::select()
+    ///     .from(Char::Table)
+    ///     .expr(PgFunc::json_agg(Expr::col(Char::SizeW)))
+    ///     .to_owned();
+    ///
+    /// assert_eq!(
+    ///     query.to_string(PostgresQueryBuilder),
+    ///     r#"SELECT JSON_AGG("size_w") FROM "character""#
+    /// );
+    /// ```
+    pub fn json_agg<T>(expr: T) -> FunctionCall
+    where
+        T: Into<SimpleExpr>,
+    {
+        FunctionCall::new(Function::PgFunction(PgFunction::JsonAgg)).arg(expr)
+    }
 }