From df7ce674e978cbd16200991d3155edc3fecccaeb Mon Sep 17 00:00:00 2001
From: Anton Markelov <doublic@gmail.com>
Date: Fri, 3 Aug 2018 16:08:47 +1000
Subject: [PATCH] add support for the multiline clickhouse queries

---
 database/clickhouse/README.md     |  9 ++++++++-
 database/clickhouse/clickhouse.go | 27 +++++++++++++++++++++++----
 2 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/database/clickhouse/README.md b/database/clickhouse/README.md
index 2b185b3..b1ebe88 100644
--- a/database/clickhouse/README.md
+++ b/database/clickhouse/README.md
@@ -1,6 +1,6 @@
 # ClickHouse
 
-`clickhouse://host:port?username=user&password=qwerty&database=clicks`
+`clickhouse://host:port?username=user&password=qwerty&database=clicks&x-multi-statement=true`
 
 | URL Query  | Description |
 |------------|-------------|
@@ -10,3 +10,10 @@
 | `password` | The user's password | 
 | `host` | The host to connect to. |
 | `port` | The port to bind to. |
+| `x-multi-statement` | false | Enable multiple statements to be ran in a single migration (See note below) |
+
+## Notes
+
+* The Clickhouse driver does not natively support executing multipe statements in a single query. To allow for multiple statements in a single migration, you can use the `x-multi-statement` param. There are two important caveats:
+  * This mode splits the migration text into separately-executed statements by a semi-colon `;`. Thus `x-multi-statement` cannot be used when a statement in the migration contains a string with a semi-colon.
+  * The queries are not executed in any sort of transaction/batch, meaning you are responsible for fixing partial migrations.
\ No newline at end of file
diff --git a/database/clickhouse/clickhouse.go b/database/clickhouse/clickhouse.go
index 5492f41..4435a77 100644
--- a/database/clickhouse/clickhouse.go
+++ b/database/clickhouse/clickhouse.go
@@ -6,6 +6,7 @@ import (
 	"io"
 	"io/ioutil"
 	"net/url"
+	"strings"
 	"time"
 
 	"github.com/golang-migrate/migrate"
@@ -17,8 +18,9 @@ var DefaultMigrationsTable = "schema_migrations"
 var ErrNilConfig = fmt.Errorf("no config")
 
 type Config struct {
-	DatabaseName    string
-	MigrationsTable string
+	DatabaseName          string
+	MigrationsTable       string
+	MultiStatementEnabled bool
 }
 
 func init() {
@@ -66,8 +68,9 @@ func (ch *ClickHouse) Open(dsn string) (database.Driver, error) {
 	ch = &ClickHouse{
 		conn: conn,
 		config: &Config{
-			MigrationsTable: purl.Query().Get("x-migrations-table"),
-			DatabaseName:    purl.Query().Get("database"),
+			MigrationsTable:       purl.Query().Get("x-migrations-table"),
+			DatabaseName:          purl.Query().Get("database"),
+			MultiStatementEnabled: purl.Query().Get("x-multi-statement") == "true",
 		},
 	}
 
@@ -97,6 +100,22 @@ func (ch *ClickHouse) Run(r io.Reader) error {
 	if err != nil {
 		return err
 	}
+
+	if ch.config.MultiStatementEnabled {
+		// split query by semi-colon
+		queries := strings.Split(string(migration), ";")
+		for _, q := range queries {
+			tq := strings.TrimSpace(q)
+			if tq == "" {
+				continue
+			}
+			if _, err := ch.conn.Exec(string(q)); err != nil {
+				return database.Error{OrigErr: err, Err: "migration failed", Query: []byte(q)}
+			}
+		}
+		return nil
+	}
+
 	if _, err := ch.conn.Exec(string(migration)); err != nil {
 		return database.Error{OrigErr: err, Err: "migration failed", Query: migration}
 	}