From f117ed317cdda81d629c4a0df676f4430a29865a Mon Sep 17 00:00:00 2001
From: Diptesh Choudhuri <ignisda2001@gmail.com>
Date: Wed, 19 Jun 2024 06:42:19 +0530
Subject: [PATCH] feat: add `json_agg` function for postgres

---
 src/backend/postgres/query.rs  |  1 +
 src/extension/postgres/func.rs | 25 +++++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/src/backend/postgres/query.rs b/src/backend/postgres/query.rs
index b843dc58..6fa5f263 100644
--- a/src/backend/postgres/query.rs
+++ b/src/backend/postgres/query.rs
@@ -117,6 +117,7 @@ impl QueryBuilder for PostgresQueryBuilder {
                     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")]
diff --git a/src/extension/postgres/func.rs b/src/extension/postgres/func.rs
index defc241e..062d2828 100644
--- a/src/extension/postgres/func.rs
+++ b/src/extension/postgres/func.rs
@@ -15,6 +15,7 @@ pub enum PgFunction {
     StartsWith,
     GenRandomUUID,
     JsonBuildObject,
+    JsonAgg,
     #[cfg(feature = "postgres-array")]
     Any,
     #[cfg(feature = "postgres-array")]
@@ -382,4 +383,28 @@ impl PgFunc {
         }
         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)
+    }
 }