From e9c28f4df85d4ac63c1b4c4e0315edc1108fd75d Mon Sep 17 00:00:00 2001
From: Chris Tsang <chris.2y3@outlook.com>
Date: Sun, 29 Aug 2021 19:19:39 +0800
Subject: [PATCH] Merge pull request #115 from
 code-mm/postgres-concatenate-operator

Postgres concatenate operator
---
 src/backend/postgres/query.rs |  7 ++++---
 src/expr.rs                   | 26 ++++++++++++++++++++++++++
 src/types.rs                  |  2 ++
 3 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/src/backend/postgres/query.rs b/src/backend/postgres/query.rs
index 9824ba8f8..6b40e7861 100644
--- a/src/backend/postgres/query.rs
+++ b/src/backend/postgres/query.rs
@@ -40,9 +40,10 @@ impl QueryBuilder for PostgresQueryBuilder {
 
     fn prepare_bin_oper(&self, bin_oper: &BinOper, sql: &mut SqlWriter, collector: &mut dyn FnMut(Value)) {
         match bin_oper {
-            BinOper::Matches => write!(sql, "{}", "@@").unwrap(),
-            BinOper::Contains => write!(sql, "{}", "@>").unwrap(),
-            BinOper::Contained => write!(sql, "{}", "<@").unwrap(),
+            BinOper::Matches => write!(sql, "@@").unwrap(),
+            BinOper::Contains => write!(sql, "@>").unwrap(),
+            BinOper::Contained => write!(sql, "<@").unwrap(),
+            BinOper::Concatenate => write!(sql, "||").unwrap(),
             _ => self.prepare_bin_oper_common(bin_oper, sql, collector),
         }
     }
diff --git a/src/expr.rs b/src/expr.rs
index 5fbbc1ce2..98a817236 100644
--- a/src/expr.rs
+++ b/src/expr.rs
@@ -1373,6 +1373,32 @@ impl Expr {
         self.bin_oper(BinOper::Contained, expr.into())
     }
 
+    /// Express an postgres concatenate (`||`) expression.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use sea_query::{*, tests_cfg::*};
+    ///
+    /// let query = Query::select()
+    ///     .columns(vec![Font::Name, Font::Variant, Font::Language])
+    ///     .from(Font::Table)
+    ///     .and_where(Expr::val("a").concatenate(Expr::val("b")))
+    ///     .to_owned();
+    ///
+    /// assert_eq!(
+    ///     query.to_string(PostgresQueryBuilder),
+    ///     r#"SELECT "name", "variant", "language" FROM "font" WHERE 'a' || 'b'"#
+    /// );
+    /// ```
+    #[cfg(feature = "backend-postgres")]
+    pub fn concatenate<T>(self, expr: T) -> SimpleExpr
+    where
+        T: Into<SimpleExpr>,
+    {
+        self.bin_oper(BinOper::Concatenate, expr.into())
+    }
+
     pub(crate) fn func(func: Function) -> Self {
         let mut expr = Expr::new();
         expr.func = Some(func);
diff --git a/src/types.rs b/src/types.rs
index ecee23039..351fdda99 100644
--- a/src/types.rs
+++ b/src/types.rs
@@ -118,6 +118,8 @@ pub enum BinOper {
     Contains,
     #[cfg(feature = "backend-postgres")]
     Contained,
+    #[cfg(feature = "backend-postgres")]
+    Concatenate,
 }
 
 /// Logical chain operator