From d9c8130d08cc85a354f02167643e4edf19b3cfd1 Mon Sep 17 00:00:00 2001
From: Ariel Mashraki <7413593+a8m@users.noreply.github.com>
Date: Thu, 13 Aug 2020 17:26:19 +0300
Subject: [PATCH] dialect/sql: configure contains-fold per dialect (#666)

---
 dialect/sql/builder.go      | 13 ++++++++++---
 dialect/sql/builder_test.go | 13 +++++++++++--
 2 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/dialect/sql/builder.go b/dialect/sql/builder.go
index c3cef2408..aa08e81f8 100644
--- a/dialect/sql/builder.go
+++ b/dialect/sql/builder.go
@@ -1138,13 +1138,20 @@ func (p *Predicate) Contains(col, sub string) *Predicate {
 func ContainsFold(col, sub string) *Predicate { return (&Predicate{}).ContainsFold(col, sub) }
 
 // ContainsFold is a helper predicate that applies the LIKE predicate with case-folding.
-// The recommendation is to avoid using it, and to use a dialect specific feature, like
-// `ILIKE` in PostgreSQL, and `COLLATE` clause in MySQL.
 func (p *Predicate) ContainsFold(col, sub string) *Predicate {
 	return p.append(func(b *Builder) {
 		f := &Func{}
 		f.SetDialect(b.dialect)
-		b.Ident(f.Lower(col)).WriteString(" LIKE ")
+		switch b.dialect {
+		case dialect.MySQL:
+			// We assume the CHARACTER SET is configured to utf8mb4,
+			// because this how it is defined in dialect/sql/schema.
+			b.Ident(col).WriteString(" COLLATE utf8mb4_general_ci LIKE ")
+		case dialect.Postgres:
+			b.Ident(col).WriteString(" ILIKE ")
+		default: // SQLite.
+			b.Ident(f.Lower(col)).WriteString(" LIKE ")
+		}
 		b.Arg("%" + strings.ToLower(sub) + "%")
 	})
 }
diff --git a/dialect/sql/builder_test.go b/dialect/sql/builder_test.go
index f4f6ad5ca..ac5759afe 100644
--- a/dialect/sql/builder_test.go
+++ b/dialect/sql/builder_test.go
@@ -802,7 +802,8 @@ func TestBuilder(t *testing.T) {
 			wantArgs:  []interface{}{"bar", "baz"},
 		},
 		{
-			input: Select().
+			input: Dialect(dialect.SQLite).
+				Select().
 				From(Table("users")).
 				Where(ContainsFold("name", "Ariel").And().ContainsFold("nick", "Bar")),
 			wantQuery: "SELECT * FROM `users` WHERE LOWER(`name`) LIKE ? AND LOWER(`nick`) LIKE ?",
@@ -813,7 +814,15 @@ func TestBuilder(t *testing.T) {
 				Select().
 				From(Table("users")).
 				Where(ContainsFold("name", "Ariel").And().ContainsFold("nick", "Bar")),
-			wantQuery: `SELECT * FROM "users" WHERE LOWER("name") LIKE $1 AND LOWER("nick") LIKE $2`,
+			wantQuery: `SELECT * FROM "users" WHERE "name" ILIKE $1 AND "nick" ILIKE $2`,
+			wantArgs:  []interface{}{"%ariel%", "%bar%"},
+		},
+		{
+			input: Dialect(dialect.MySQL).
+				Select().
+				From(Table("users")).
+				Where(ContainsFold("name", "Ariel").And().ContainsFold("nick", "Bar")),
+			wantQuery: "SELECT * FROM `users` WHERE `name` COLLATE utf8mb4_general_ci LIKE ? AND `nick` COLLATE utf8mb4_general_ci LIKE ?",
 			wantArgs:  []interface{}{"%ariel%", "%bar%"},
 		},
 		{