Ensure that schema search path is set with every connection on postgres (#14131)

* Ensure that schema search path is set with every connection on postgres

Unfortunately every connection to postgres requires that the search path is
set appropriately.

This PR shadows the postgres driver to ensure that as soon as a connection
is open, the search_path is set appropriately.

Fix #14088

Signed-off-by: Andrew Thornton <art27@cantab.net>

* no golangci-lint that is not a helpful suggestion

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Use Execer if available

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: techknowlogick <techknowlogick@gitea.io>

2 files changed, 85 insertions, 11 deletions

diff --git a/models/models.go b/models/models.go
index 6aaa26d627..f12a4e8b30 100644
--- a/models/models.go
+++ b/models/models.go
@@ -145,7 +145,16 @@ func getEngine() (*xorm.Engine, error) {
 		return nil, err
 	}
 
-	engine, err := xorm.NewEngine(setting.Database.Type, connStr)
+	var engine *xorm.Engine
+
+	if setting.Database.UsePostgreSQL && len(setting.Database.Schema) > 0 {
+		// OK whilst we sort out our schema issues - create a schema aware postgres
+		registerPostgresSchemaDriver()
+		engine, err = xorm.NewEngine("postgresschema", connStr)
+	} else {
+		engine, err = xorm.NewEngine(setting.Database.Type, connStr)
+	}
+
 	if err != nil {
 		return nil, err
 	}
@@ -155,16 +164,6 @@ func getEngine() (*xorm.Engine, error) {
 		engine.Dialect().SetParams(map[string]string{"DEFAULT_VARCHAR": "nvarchar"})
 	}
 	engine.SetSchema(setting.Database.Schema)
-	if setting.Database.UsePostgreSQL && len(setting.Database.Schema) > 0 {
-		// Add the schema to the search path
-		if _, err := engine.Exec(`SELECT set_config(
-			'search_path',
-			? || ',' || current_setting('search_path'),
-			false)`,
-			setting.Database.Schema); err != nil {
-			return nil, err
-		}
-	}
 	return engine, nil
 }
 
diff --git a/models/sql_postgres_with_schema.go b/models/sql_postgres_with_schema.go
new file mode 100644
index 0000000000..0c8893ea27
--- /dev/null
+++ b/models/sql_postgres_with_schema.go
@@ -0,0 +1,75 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package models
+
+import (
+	"database/sql"
+	"database/sql/driver"
+	"sync"
+
+	"code.gitea.io/gitea/modules/setting"
+
+	"github.com/lib/pq"
+	"xorm.io/xorm/dialects"
+)
+
+var registerOnce sync.Once
+
+func registerPostgresSchemaDriver() {
+	registerOnce.Do(func() {
+		sql.Register("postgresschema", &postgresSchemaDriver{})
+		dialects.RegisterDriver("postgresschema", dialects.QueryDriver("postgres"))
+	})
+}
+
+type postgresSchemaDriver struct {
+	pq.Driver
+}
+
+// Open opens a new connection to the database. name is a connection string.
+// This function opens the postgres connection in the default manner but immediately
+// runs set_config to set the search_path appropriately
+func (d *postgresSchemaDriver) Open(name string) (driver.Conn, error) {
+	conn, err := d.Driver.Open(name)
+	if err != nil {
+		return conn, err
+	}
+	schemaValue, _ := driver.String.ConvertValue(setting.Database.Schema)
+
+	// golangci lint is incorrect here - there is no benefit to using driver.ExecerContext here
+	// and in any case pq does not implement it
+	if execer, ok := conn.(driver.Execer); ok { //nolint
+		_, err := execer.Exec(`SELECT set_config(
+			'search_path',
+			$1 || ',' || current_setting('search_path'),
+			false)`, []driver.Value{schemaValue}) //nolint
+		if err != nil {
+			_ = conn.Close()
+			return nil, err
+		}
+		return conn, nil
+	}
+
+	stmt, err := conn.Prepare(`SELECT set_config(
+		'search_path',
+		$1 || ',' || current_setting('search_path'),
+		false)`)
+	if err != nil {
+		_ = conn.Close()
+		return nil, err
+	}
+	defer stmt.Close()
+
+	// driver.String.ConvertValue will never return err for string
+
+	// golangci lint is incorrect here - there is no benefit to using stmt.ExecWithContext here
+	_, err = stmt.Exec([]driver.Value{schemaValue}) //nolint
+	if err != nil {
+		_ = conn.Close()
+		return nil, err
+	}
+
+	return conn, nil
+}