Add support for RETURNING clause in bulk insert queries (#11)

- Add RETURNING clause detection to suffix boundary logic
- Preserve RETURNING clause when building bulk insert queries
- Add test cases for RETURNING clause with and without ON CONFLICT
- Add additional test cases for ON DUPLICATE KEY UPDATE with case variations
- Ensures RETURNING clause is properly handled similar to ON DUPLICATE KEY UPDATE and ON CONFLICT

Author: tomtwinkle

templates/template.go

@@ -67,6 +67,7 @@ func buildBulkInsertQuery(originalQuery string, numArgs int, numParamsPerArg int
 	// Use LastIndex to find the main clause
 	onDuplicateUpperIndex := strings.LastIndex(strings.ToUpper(trimmedQuery), "ON DUPLICATE KEY UPDATE")
 	onConflictUpperIndex := strings.LastIndex(strings.ToUpper(trimmedQuery), "ON CONFLICT")
+	returningUpperIndex := strings.LastIndex(strings.ToUpper(trimmedQuery), "RETURNING")
 
 	// Find the earliest starting position of any suffix keyword
 	suffixBoundary := len(trimmedQuery)
@@ -76,6 +77,9 @@ func buildBulkInsertQuery(originalQuery string, numArgs int, numParamsPerArg int
 	if onConflictUpperIndex != -1 && onConflictUpperIndex < suffixBoundary {
 		suffixBoundary = onConflictUpperIndex
 	}
+	if returningUpperIndex != -1 && returningUpperIndex < suffixBoundary {
+		suffixBoundary = returningUpperIndex
+	}
 
 	if suffixBoundary < len(trimmedQuery) {
 		// Suffix found

templates/template_test.go

@@ -161,6 +161,30 @@ func TestBuildBulkInsertQuery(t *testing.T) {
 					}
 			},
 		},
+		"valid:upsert (ON DUPLICATE KEY UPDATE)": {
+			arrange: func(t *testing.T) (Args, Expected) {
+				return Args{
+						originalQuery:   "INSERT INTO users (id, name) VALUES (?, ?) ON DUPLICATE KEY UPDATE id = VALUES(id), name = VALUES(name);",
+						numArgs:         2,
+						numParamsPerArg: 2,
+					}, Expected{
+						query: "INSERT INTO users (id, name) VALUES (?,?),(?,?) ON DUPLICATE KEY UPDATE id = VALUES(id), name = VALUES(name)",
+						err:   nil,
+					}
+			},
+		},
+		"valid:upsert (ON DUPLICATE KEY UPDATE) case-insensitive": {
+			arrange: func(t *testing.T) (Args, Expected) {
+				return Args{
+						originalQuery:   "insert into users (id, name) values (?, ?) on duplicate key update id = values(id), name = values(name);",
+						numArgs:         2,
+						numParamsPerArg: 2,
+					}, Expected{
+						query: "insert into users (id, name) VALUES (?,?),(?,?) on duplicate key update id = values(id), name = values(name)",
+						err:   nil,
+					}
+			},
+		},
 		"valid:upsert (ON CONFLICT)": {
 			arrange: func(t *testing.T) (Args, Expected) {
 				return Args{
@@ -185,6 +209,30 @@ func TestBuildBulkInsertQuery(t *testing.T) {
 					}
 			},
 		},
+		"valid:RETURNING clause": {
+			arrange: func(t *testing.T) (Args, Expected) {
+				return Args{
+						originalQuery:   "INSERT INTO users (id, name) VALUES (?, ?) RETURNING id;",
+						numArgs:         2,
+						numParamsPerArg: 2,
+					}, Expected{
+						query: "INSERT INTO users (id, name) VALUES (?,?),(?,?) RETURNING id",
+						err:   nil,
+					}
+			},
+		},
+		"valid:RETURNING clause with ON CONFLICT": {
+			arrange: func(t *testing.T) (Args, Expected) {
+				return Args{
+						originalQuery:   "INSERT INTO users (id, name) VALUES (?, ?) ON CONFLICT (id) DO UPDATE SET name = EXCLUDED.name RETURNING id;",
+						numArgs:         2,
+						numParamsPerArg: 2,
+					}, Expected{
+						query: "INSERT INTO users (id, name) VALUES (?,?),(?,?) ON CONFLICT (id) DO UPDATE SET name = EXCLUDED.name RETURNING id",
+						err:   nil,
+					}
+			},
+		},
 		"valid:Squeeze spaces": {
 			arrange: func(t *testing.T) (Args, Expected) {
 				return Args{